affordable residential construction vol2

8/8/2019 Affordable Residential Construction Vol2

1/94

Challenge andResponse -Volume II

AffordableResidential

Constructon

A Guide forHome Builders

Joint Venture forAffordable Housing


2/94

One of my h i gh e s t p r i o r i t i e s when I came t o HU D i n 1981 was t o makeh o u s in g a f f o r d a b l e a g a in . A s p a r t o f t h i s e f f o r t , i n Ja n u a ry 1982 Ia nn ou nc ed t h e f o r m a t i o n o f t h e J o i n t Ve nt ur e f o r A f f o r d a b l e H o us in g as ap u b l i c - p r i v a t e p a r t n e r s h i p t o f i n d ways t o o vercome t h e c o s t im p ac t o fo u t d a t e d a nd u n n ec e ss a ry b u i l d i n g and l a n d u se r e g u l a t i o n s .

O ve r t h e p a s t f i v e y e a r s, we a t HU D h av e w ork ed w i t h b u i l d e r s a ndl o c a l government o f f i c i a l s i n more t h an 30 c o m m u n i t i e s a c r o s s t h e n a t i o ni n a su c ce s sf ul e f f o r t t o d e mo ns tr ate t h a t r e g u l a t o r y r e f o r m c an r e du ceh o u s i n g c o s t s b o t h i n new s u b d i v i s i o n s a n d f o r new homes i n e s t a b l i s h e dn e i gh b o r ho o d s. The A f f o r d a b l e H o u s in g D e m o n s t r at i o n p r o j e c t s p r o v e d t h a tt h i s a p pr oa ch w o rk s; t h e J o i n t Ven tu re c on ce pt o f a c o o p e r a t i v e e f f o r t t or e d u ce h o u s i ng c o s t s i s n ow an o p e r a t i n g p r o gr am o f t h e D e pa rt me n t.

r e p o r t e d i n a s e r i e s o f i n d i v i d u a l c a se s t u d i e s , h ave now be en co mb in edi n tw o f i n a l r e p o r t s w i t h t h e g en er al t i t l e , A ff o r da b le H ou sin g:Chal lenge and Response .

L o c a l G ove rn me nt a n d D e v e l o p e r s ," d e s c r i b e s t h e l a n d u se , s i t e

d e v el o pm e n t, a nd a d m i n i s t r a t i v e a nd p r o c e d u r a l c ha n ge s used i n t h eA f f o r d a b l e Housing Demonstrations .C o n s t r u c t i o n : A G u id e f o r Home B u i l d e r s , " a d d re s se s t h e ch a ng e s i nb u i l d i n g d e s ig n , m a t e r i a l s , c o n s t r u c t i o n sy ste m s, and m a r k e t i n g m eth od sw h ic h p r o ve d s u c c e s s f u l i n t h e d e m o n s tr a ti o n p r o j e c t s .

a b o ut t h e ch an ge s n e ce s sa r y t o r e a c h t h e g o a l o f a f f o r d a b l e h o u s i n g f o r

The le s so n s le a r n e d i n t h e d e m o n st ra t io n p r o j e c t s , o r i g i n a l l y

Volume I , " A f f o r d a b l e R e s i d e n t i a l L a n d D e v e l o p m e n t : A G u i d e f o r

Volume I I , " A f f o r d a b l e R e s i d e n t i a l

I b e l i e v e t h a t t h e i n f o rm a t i o n i n t he s e r e p o r t s w i l l h e l p b r i n g

everyone .


3/94

AFFORDABLEH O U S I N G

CHALLENGEAND RESPONSE

Volume I I

Affordable ResidentialConstruction: A Guidefo r Home Builders

Prepared for:U.S. Department ofHousing and Urban DevelopmentInnovative Technology andSpecial Projects Division

By:NAHB National Research Center40 0 Prince Georges Ctr. Blvd.Upper Marlboro, Md. 20772

July 1987


4/94

Foreword

For years the U.S. Department of Housingand Urban Development (HUD), the NationalAssociation of Home Builders (NAHB), andthe NAHB National Research Center(formerly the NAHB Research Foundation,Inc.) have been searching for solutions tothe rising cost of housing.

The Joint Venture for Affordable Housing(JVAH) program has been a significant

step toward lowering housing costs. Thismanual contains a compilation of provencost-saving construction techniques. Allthe techniques may not be applicable inevery situation, but most builders willlikely find many ways to lower housingcosts. Volume I, the companion manual,contains proven cost-reduction methods ofland planning and development as well asactions local governments can take toencourage more affordable housing.

Acknowledgements

This manual is the result of materialobtained from the Joint Venture forAffordable Housing Demonstration buildersand from other sources. It was preparedfor the Department of Housing and UrbanDevelopment by the NAHBNationalResearch Center. The demonstrationprogram was directed by the Office ofPolicy Development and Research.

The principal author was E. Lee Fisher,with assistance from Carol B. Schaake,Richard A. Morris, and untold others whoprovided years of residential research effort

and documentation. Most importantly, wewish to thank the builders of the JVAH

demonstration and the communities whotook the risks and put their resources onthe line to prove that affordable housingfor all Americans can be a reality.

The work that provided the basis of thispublication was supported by funding undera contract with the U.S. Department ofHousing and Urban Development. Thesubstance and findings of that work arededicated to the public. The authors aresolely responsible for the accuracy of thestatements and interpretations contained inthis publication. Such interpretations do

not necessarily reflect the views of theGovernment.


5/94

TABLE OFCONTENTS

v

1

26

36

43

53

56

58

67

69

73

81

83

INTRODUCTION

HOUSE AND LOT DESIGN

FOOTINGS AND FOUNDATIONS

WOOD FRAME FLOORS

WALLS AND PARTITIONS

FIREWALLS

ROOF FRAMING

PLUMBING

ELECTRICAL

HEATING, VENTILATlON,AND AIR CONDITIONING

BUSINESS/MARKETING

REFERENCES

APPENDIX I


6/94


7/94

INTRODUCTION

HUDs Joint Venture for AffordableHousing (JVAH) demonstration was aprogram designed to help reevaluatebuilding regulations and typicalbuilder practices in an attempt tofind solutions for building afford-able homes. Many cost savingconstruction methods had beendeveloped over the years but had notbeen adopted by local codes or hadnot been put into practice bybuilders. The U.S. Department of

the National Association of HomeBuilders (NAHB), and the NAHB

compiled those ideas and, workingwith builders, developers andcommunity officials all over thenation, instituted many of them withoutstanding results.

The JVAH demonstration program wasextremely successful in encouragingunderstanding and cooperation betweendifferent interest groups in finding

solutions to high housing costs.This was accomplished by restructur-ing processing procedures, using landmore efficiently, revising outmodedland development practices, and usingproven cost-saving constructiontechniques. encourage innovation.

This guide contains methods to reducecosts in most phases of directconstruction of the house itself.Cost-saving land use and developmenttechniques and streamlined processingprocedures are presented in acompanion manual (See Volume I).Most of the methods described hereinwere demonstrated in at least one ofthe JVAH sites. Many were repeatedin almost all of the sites. Theguide is not intended to be thedefinitive construction manual, but

rather a compilation of techniquesthat were proven effective in theJVAH program and in other areas.

Most homes in the demonstrationprogram were "stick-built" on site.Somewere factory-built, .e.,modular, HUD Code, or panelized.

The manual is written for those whoare already familiar with construc-tion terminology and "typical" ways

section at the end of the manualcontains titles and sources of other

complete backup information and data.

It is likely that some of themethods discussed herein are notpresently acceptable under some localregulations. Before attempting toadopt any new technique, check thelocal code or with local buildingofficials. If not acceptable, it

will be worthwhile to work with thelocal authorities for change.Success of an affordable housingprogram depends upon builders,government officials, and concernedcitizens taking necessary steps to

The manual is organized along thelines of how a house is builtstarting with design, then footingsand foundations, floors, walls,etc. Each section contains ageneral discussion of the topicfollowed by specific cost-saving

innovations, and then JVAH case studyexperiences. Hopefully each readerwill find several ideas that willresult in reducing housing costswithout sacrificing health, safety,and general welfare features.

Housingand Urban Development (HUD), of building homes. A eference

NationalResearch Center (NAHB/NRC), manuals that will provide more


8/94


9/94


10/94

For smaller homes, it becomes moreimportant to orient central livingareas to outdoor spaces or views.Single-story homes preserve privacybecause they do not look out overfences and more rooms can be placedaround patio space.

Second story windows should beoriented away from neighbors yardsand toward natural views wheneverpossible. By promoting outdoor livingwith decks, patios, porches, andgarden seats, small homes becomemuch more attractive and lose thesmall feeling.

A well-designed floor plan willconsider the functions of differentareas of the house; i.e., sleeping,living, working, dining and circulationspaces and their relationships to eachother.

By orienting major living areas to thesouth, you can take advantage of thewinter sun and provide a measure ofpassive solar heating. Likewise, byplacing storage space and seldom usedwindowless rooms on the northelevation, heat loss to the sunless sideof the house will be minimized. Thesetechniques will, of course, be moreimportant in certain climates thanothers.

Where heating is of little consequence,

orientation is not as important.Where heating and cooling are both


11/94

important, shading of south facingwindows in the summer becomes veryimport ant.

Minimize the distance between parkingand the kitchen. This not onlyprovides relief from carrying heavyshopping bags, but also reducestracking in dirt across carpeted areas.An entrance from parking through awork zone such as a laundry roomprovides an area for muddy shoes andheavy outer garments.

Circulation area is, in effect, wastedfor most other uses. The exceptionmight be a pass-through work area.Otherwise, small homes cannot affordthe luxury of space that is intendedsolely to travel from one area toanother. Good design will hold suchspace to the absolute minimum withoutundue traffic through living areas.Placement of entry doors and closetswill dictate traffic patterns.

Small homes often seem more spaciousby careful use of sight distances.That is, when in a closed-in room, itdoes not matter whether the housecontains 1,000or 2,000 square feet.Perception of size ends at the walls.Therefore, eliminate interior walls andprovide angles where the occupant canlook through other spaces, preferablyto the outdoors through a largewindow or sliding glass door.However, looking through a workspace is not normally considereddesirable.


12/94


13/94

Room -By-Room Analysis Good plans are made up through room-by-room analyses. How can you tell agood room from a bad one? Before aroom can qualify as being wellplanned, it must pass two tests:

1. Does circulation work inside theroom?

2. Is there a place to put furnitureand arrange it properly aftercirculation and stairs are takencare of?

Possibly the most important room isthe living area, but it is not neces-sarily the most difficult room to plan.Kitchens, laundries, bedrooms,bathrooms, family rooms, and storageareas all present planning problems.

The good living room is free fromthrough traffic and designed for bestfurniture arrangement. It will bedesigned for both interior Views (T.V.,fireplace, feature areas) and exteriorviews. In a good layout, furnituredoesnt have to be moved every time


14/94

you wish to look at your favorite T.V.program, watch the fire, or look outthe window.

A good kitchen is not necessarily"glamorous" or "gadgety," althoughsome glamour or gadgets may bemarketable. Primarily, a good designis one that works. Is it laid outefficiently? Does it have the rightkind of storage in the right places andin the right amounts? Does it makethe user feel like a prisoner or does itmake the time spent relativelypleasant? Is it located properly in

relation to the rest of the plan?Above all, is the kitchen the controlarea for the rest of the house?

Modern laundries are designed to saveprecious small home space. But thisdoes not mean laundries should becrammed into a left-over corner. Thelaundry-utility core should be locatednear the kitchen or a bathroom.Garages or basements are alternativelocations although they have draw-backs. Arrange laundry applianceslogically with good outside light ifpossible.


15/94

Bedroom space in small homes is oftentoo small. Don't throw away space inexcessive hallways. Large windowsmake the bedroom look bigger andprovide plenty of light and ventilation.Master bedrooms should containadequate space for at least queen-sizeor twin beds.

The argument for small windowsbecause of privacy considerations isnot valid since curtains or drapes arepulled over even the smallest windows.A good bedroom will have unob-structed closet space. Other livestorage, where circulation is likely to

attic storage with pull-down stairsmay be feasible. The most importantthings to remember about storage are:

1. There is never enough of it.

2. It should be located according to

3. It should be designed, dimen-sioned, and subdivided accuratelyfor articles to be stored, not justvaguely tossed into a plan as a"closet" or "shelf .

frequency of use.


16/94

Exterior Appearance Design does not end with a good floorplan. The exterior style and combina-tions of shape and mass are equallyimportant. Pleasing visual proportionsand textures are not limited to larger,luxury homes. Uncluttered, simpleappearances can be pleasing in small,less expensive homes too.


17/94

Do not ignore what has been success-ful in the community, but also do notarbitrarily assume that certain sidings

and styles will not work. Builders aretraditionally much more conservativethan the home buying public. This isunderstandable when one considers therisk involved in doing somethingdifferent. An award winning design isuseless if it does not sell. Butpent-up demand for different styles ofhomes often goes untapped because oftoo much conservatism.

In the JVAH, Santa Fe builder Mike

Chapman risked putting a contem-porary, plywood-sided, sloped-roofhouse on the market in anadobe/stucco, flat-roofed, Spanisharchitecture community. He was ofthe o inion that the only reason this

that it had not been built. Heconducted a marketing survey thatindicated there was, indeed, a pent-upmarket. The 47-unit first phase soldout in two weeks. The entire 154-unitsubdivision sold out one year ahead of

schedule. Chapman paid a lot ofattention to both interior and exteriordesign.

Good design rules are not carved instone for all houses and communities.A California contemporary designmight not sell on Cape Cod. A CapeCod cottage might be out of lace in

take advantage of a market that allothers ignore because of "tradition."

Basically, however, there are somerules that transcend local preferences.

style homewas not ''marketable" was

Arizona. But an astute builder will


18/94

For the roof, provide a strong fasciaon overhangs. Depth and style ofoverhangs should complement theoverall appearance. A cascade ofroofs at the same slope can bevisually pleasing if not overdone.

Normal transitions, say from the houseto the garage, are the best places tochange roof lines. Roof overhangchanges for a porch or sun shading ofwindows also create a visual break.Remember, however, each change inroof lines adds to costs.

The home entry should be clearlyrecognizable at first glance. Full-height windows and sliding glass doorson the front of the house need to beeasily distinguished from the primaryentry. This can be done by creating atransition space to the front entry byusing paths, steps, or landscaping.

Once inside, there should be anentrance "space" that clearly definesthe area. A separate vestibule or

entrance room is not necessary, butthe area needs to be defined by achange in floor surface, railings,closets, etc. Ideally, entrance"control" should be maintained fromthe kitchen. That is, the primaryentry should be visible from theprimary work area -- the kitchen.


19/94

Since the garage is often the mainentrance for much of the family, itcan be designed as a positive entry

rather than just a passage door to thegarage.

Keep window and door heads in line.Wall thickenings add interest (but alsoadd cost), as do front entry setbacks.Carefully select windows to fit overalldesign and locate them for bestnatural ventilation and for architec-tural balance.

The rear elevation is often the"forgotten" elevation. Because muchtime is often spent in the back yardand because the rear elevation isoften viewed by the neighbors or fromanother street, care should be takento make it attractive also.

For small homes, it is difficult tomaintain good width/height balance.If the house sits on a high foundation,proportions often are not the best andthe house looks "boxy" and evensmaller. A lowerprofile elevationtends to make the house appear larger.The building to ground connection canbe softened by landscaping, steps,terracing, etc. This tends to reducethe high boxy look.


20/94

Within the framework of goodmarketable design, there are methodsto ensure that costs are loweredwithout sacrificing marketability.

First, use modular dimensioning. Mostbuilding materials are produced inincrements of 2 feet, including trim,lumber, sheathing, and some sidings.The most efficient use of thesematerials will be obtained if overallhouse dimensions are laid out on a2-foot grid. The, most efficient planis a basic rectangle which allowssimple floor and roof structures on

the 2-foot grid.

For design variation, two offsetrectangles provide a break in rooflines as well as an elevation change.A n offset garage also can be used tobreak up the flat front look. Keep inmind, however, that each variationfrom the basic rectangle adds cost.Depth of the most cost effectiverectangle is limited by the allowablespan of roof and/or floor framingmembers.

House shape and configuration effecttotal cost for the same amount offloor space. For example, an "H shapedlan has 46 more linear feetof wall, 8 more corners, 4 moreroofing areas, 2 more gable ends, and4 more valleys than a rectangularplan.

The most cost-effective plan is onethat encloses the desired floor area


21/94

with the least amount of exteriorwall. The ratio of loor to wallshould be as high as possible withindesign parameters. For example, a28x40 plan has 1,120 square feet offloor area and 136 linear feet of wallfor a floor/wall ratio of 8.24. A24x46 has 1,104 square feet of floorarea and 140 linear feet of wall, aratio of 7.89. The 28x40 plan is moreefficient.

The high floor-to-exterior-wall ratioapproach can also apply to the interiorpartitions. That is, the "open

planning" concept of space limits thetotal length of interior partitions. Asmentioned earlier, this is also atechnique to make a small house seembigger inside.

Defining areas by floor textures,railings, ceiling height changes, etc.,eliminates the need for some interiorpartitions. It also results in lowercosts for framing, drywall,painting,and, very importantly, for electricalwiring.

Plans that provide for future expan-sion may be desirable in somemarkets. If done, give special

circulation, and plumbing and heatingextensions. It can be a usefulmarketing tool, especial1 to first time

home buyers with small families.Future usable space within theexterior shell was provided in theSanta Fe, Lincoln, Tulsa, andBaltimore County JVAH demonstrations.

attention to problems ofaccess,


22/94

Slab-on-grade esigns minimize costand foundation problems in many areasof the country. If basements areperceived necessary because ofmarketing or site considerations, usemulti-level designs which increasehabitable space at minimal cost.

If the foundation type is optional,remember that it is almost always lessexpensive and more desirable to addhabitable space above ground thanbelow ground.

Use cantilevered loors over base-ments, crawl spaces, or first floorson two-story homes to provide designvariations or to increase floor area atminimal extra cost. Cantilevers of upto 2 feet are generally permissibleand help reduce out-of-squarefoundation problems. Cantileveredfloors must be well insulated toprevent heat loss and frozen pipes.

When laying out interior partitions,locate them to intersect with an


23/94


24/94

exterior wall stud (on the 2-footgrid). This provides a tie-in withoutextra framing or blocking and providesone side of drywall backup.

At least one side of window or doorframing can coincide with normalmodular framing in almost every case.It may be necessary to move therough opening a few inches in onedirection or the other to save a studor two and, in most cases, thearchitectural balance will not beaffected enough for anyone to notice.

If trusses are used, able end walls

this, structural headers over openingsare not necessary. Therefore, locatelarge openings in the gable ends ifconsistent with exterior design andfloor plan.

Likewise, interior partitions areusually nonbearing. Openings do notrequire structural headers. If aload-bearing interior wall is necessary,limit the number of openings in thatwall.

Most major model codes allow a 7'6"ceiling height. For small homes, thisheight may provide a better exteriorscale. It also reduces siding and mayeliminate one step from stairs in atwo-story home. However, extra costscan be expected on drywall applica-tion. Studs must be trimmed unlessthey can be purchased precut for 7'6"ceiling heights.

When possible, plan for straight-runstairs,

parallel to floor framingmembers, and coordinate the stairswith normal joist positions on oneside to reduce floor joist disruptions.As shown in the framing section, stairtrimmers and headers can be reducedif properly laid out.

are essentially nonbearing.Because of

Attic/crawl space access doors shouldbe located between framing membersto eliminate structural headers. Ifframing members are spaced 24 incheson center, ample access space isprovided.

Consider centralized back-to-back"plumbing around a common stack tominimizepiping requirements. Intwo-story homes, arrange upper levelover lower level plumbing connected tothe same stack. It will be necessary,no doubt, to point out these featuresto the plumbing contractor in orderto get a reduced bid from him. Alsolay out plumbing to minimize disrup-tions to structural members. Con-centrate as much plumbing as possiblein the same wall.

Plan chases for ducts and lues toallow ample clearances and to avoiddisruption or displacement of struc-tural members. Too often, ductplacement is an afterthought whichrequires expensive solutions.

When practical, locate heating/coolingequipment in a central location toreduce duct runs and sizes and toprovide good distribution. For smallhouses, a centralized system oftenmeans duct runs of less than 10 feetif high inside wall or ceiling registersare used. However, be sure to followmanufacturers' recommendationsconcerning placement because someequipment is designed specifically foroutside wall locations.

Develop complete working drawingsand specifications covering allimportant details for the constructionprocess. Where possible, concentratedetails for specific trades on a singledrawing. Avoid tight or highly criticaldimensions where possible (such ascabinets between walls). If such


25/94

critical dimensions are necessary, showin bold lettering, by underlining, orby some other method that leaves nodoubt that these dimensions must beaccurate.

All design recommendations applyequally to site-built, factory-built(modular and HUD code), and com-ponentized housing. Most JVAHdemonstration sites consisted of site-built homes, but modular units wereused in Springfield, MA, Orange, NJ;

and Elkhart, IN. HUD code-manufac-tured units were used in OklahomaCity, Stevenville, TX,and Elkhart.Panelized units were erected in SiouxFalls, SD, and White Marsh, MD.

The first step toward cost-effectiveconstruction is efficient design. Manycostly details can be corrected in thedesign process. Therefore, theimportance of merging good design formarketability and efficient design forconstruction cannot be overemphasized.


26/94

EXAMPLES FROM THEDEMONSTRATION PROJECTS

Santa Fe, New Mexico

Builders in the affordable housingdemonstration were not given specificdesigns to build. Rather, they wereasked to design homes they thoughtwould be marketable in their areas,and to submit these designs to HUDand NAHB/NRC for evaluation andsuggested cost-saving revisions.

Since the builders were not subsidized,they could accept or reject sugges-tions. Most were very successful inoffering high-quality, well-designedhomes at affordable prices.

Mike and Walton Chapman wereexceptionally daring, building homes

Lacey, Washington The JVAH site was a mixture oftownhouses, quadplex, zero-lot-line,and pinwheel cluster cottages. Densitywas eight units per acre.


27/94

The cottages contained two bedroomsand one bath in 880 square feet.John Phillips, the builder/developer,

had previously built another sub-division of these small, inexpensivehomes and received national attentionin Professional Builder magazine as anaward-winning project.

Sixty-four of the 176 units were thesecottages. They were basically squarein design, giving the best floor areato exterior wall ratio. A small 4-footoffset provided a break in the frontelevation and also allowed a break inthe roof lines.

The floor plan was very functionalwith minimal circulation area. Theliving/dining areas were combined into

a "great room" of approximately 360square feet. A vaulted ceiling overthe 14x18 living room area added to

the feeling of spaciousness.A sliding glass door off the living arealeading to a small fenced-in yard alsohelped in making a small home seemvery large. A window off the kitchenarea facing the front door providedentrance control.

Although it contained only one bath,Phillips provided a second lavatory ina dressing room off the large masterbedroom walk-in closet. The bathroomfeatured a skylight, cultured marbleshower surround, and a "step-upbathtub which added a sense o luxuryat minimal extra cost.

P


28/94

The one-bedroom "loft" home quadplexunits were designed for singles,newlyweds, and others who neededminimal space. They were arranged ina back-to-back configuration, eachwith its own private entrance andsmall yard.

The smallest loft home contained 648square feet and the largest, 674 squarefeet. The main level consisted of aliving room with a vaulted ceiling, adining area with vaulted-open beamceiling and a kitchen. The upper loftarea contained one bedroom and abath.

The bedroom was open to the livingarea below, separated by a 4-foot highwall. This provided, in effect, onelarge open area for all rooms in theunit. The only full height interiorpartitions were for the bathroom andclosets.

The zero-lot-line homes contained twobedrooms and one bath with a smallloft overlooking the living area.Each featured a two-car garage.Floor plans were more traditional thanother styles within the project, butthe loft added interest and the vaultedceilings created space.


29/94

Phoen ix, Arizona

with openness in mind. Living roomsleading into dining areas and vaultedceilings with lofts made the smalltwo-bedroom units seem much larger.

Knoell Homes designed the house planswith the goal of making the smallunits attractive and saleable whilepayingattention to productionefficiencies.

Innovative use of interior space, suchas vaulted ceilings and living areasopening onto outdoor patios, created asense of openness.

Three models of townhouses and threebasic models of zero-lot-line detachedhomes ranged in size from 770 to1,295 square feet. The largestdetached home had alternative floorplans providing either two or three

Bedrooms.


30/94


31/94

The market was determined to be firsttime buyers, including singles andnewly marrieds. The one-bedroomunit contained 896 square feet. Thelower level consisted of a large living/dining great room and the kitchen.The upper level contained one largebedroom and a large bathroom/laundry.

The two-bedroom unit contained 1,088square feet. The lower level con-tained a 15 1/2x18 great room,kitchen, and powder room. The upperlevel contained two bedrooms, a singlebathroom and separate vanities foreach bedroom.


32/94

Crittenden County, Arkansas

acres. Three basic zero-lot-linedetached models were built, ranging insize from 1,076to 1,624 square feet.Sunridge homes were designed to makethe units energy efficient, attractive,marketable, and affordable.

The builder, Rich Boyden, wasespecially attentive to details thatappealed to his target market,including interesting angles, privacy,and an abundance of light.

All units were designed with the bulkof the glazing facing south formaximum passive solar gain. Clere-story windows and other large areasof glass made the homes very energyefficient. In addition, Boyden installedsmall wood burning stoves in all unitswhich proved to be a very desirablefeature. Interviews with occupantsindicated that, during the winter of1985-86,total heating costs werebetween $15 and $50per month,depending on the use of the woodburning stove. The south-facingwindows are shaded in the summer.

Rex Rogers determined that there wasa market for very small (504 squarefeet to 960 square feet) homes onsmall lots. Rogers believed basic,no-frills housing would sell in hisarea.


33/94

Four models were offered: a 504-square-foot efficiency unit, a 638-square-foot two-bedroom unit, a 782-

square-foot three-bedroom unit, and a960-square-foot three-bedroom unit.The efficiency unit, which was nothingmore than one large room with anaccordion wall separating the bedroomarea did not sell. However, the otherunits sold well.

A popular option was a loft whichadded from 384 to 528 square feet.The homes sold from about $27,000 toabout $35,000 without the loft orgarages.

Although the units were small andbasic in design, they were built withquality materials and workmanship.Exterior walls were built with 2x6framing, 24 inches on-center, andcontained R-19 insulation.

The floor plans have proven to bemarketable in other areas of Arkansas.Through the efforts of HUD AreaOffice Manager, John Suskie, theJVAH program has become extremelysuccessfulin the region.


34/94

FOOTINGS AND FOUNDATIONS

Because the foundation transfers theweight of the house to the soil,prudent engineering principles andcalculations are necessary. However,prescriptive code requirements oftencodify the worst case situation, addingunnecessarily to costs for all founda-tions built in an area. The optimumfoundation will depend on factors suchas climate, soil, topography, andbuilding loads.

Basically, concrete footing widths aredetermined by total design loads inpounds per linear foot o footing andallowable soil bearing capacity inpounds per square foot. Columnfooting sizes are determined by totaldesign load in pounds and allowablesoil bearing capacity in psf. SeeTables 1 and 2.

As shown in the above tables, if soil bearing tests are made, footing widthsmay be reduced substantially thereby reducing costs, assuming local codes areperformance based.


35/94

The 1986CABO One and Two FamilyDwelling Code prescribes minimumfooting widths and depths, butSection R-108, AlternateMaterials andSystems, provides a mechanism forinnovative design and material usage.All major model codes have similarprovisions that should be usedwhenever soil bearing tests orengineering calculations areappropriate.

Reinforcing of concrete footings isrequired by some local codes or isroutinely installed as "localpractice." Footing reinforcement isseldom necessary for footings placedon undisturbed soil. Compacted filloften has sufficient bearing capacitythat makes reinforcing unnecessary.

Footings in expansive soil conditionsshould always be designed by qualifiedengineers and will most likely require

reinforcing. Otherwise, elimination offooting reinforcing rods is a legitimatemethod of reducing costs in manycases.

As with footings, reinforcement infoundation walls is seldom necessary innonexpansive soil and in areas outsideof seismic zones 2,3 or 4. If rein-forcement is routinely installed inaccordance with local code require-ments or local practice, it will beworthwhile to examine soil conditionsand work toward change.

Under stable base conditions, concreteslab floorsdo not require welded wiremesh. It is not recognized as struc-tural reinforcement and provides nosignificant function. If installedcorrectly (in the upper third of theslab), welded wire mesh may be ofminor value in limiting the width ofcracks.


36/94


37/94

Waterproofing Throughout the years, there have beenmany attempts to develop the defini-tive basement waterproofing method.

Some methods have worked better thanothers, but basement leakage continuesto be one of the most commoncustomer complaints.

Capillary water and condensation ncomparatively cool walls and floorscreate dampness. Most capillaryproblems diminish or go away whenconcrete completely cures or whenpositive drainage steps are taken. Aplastic film vapor barrier under thebasement slab and on walls reducescapillary action through the concrete.Condensation dampness is a functionof internal humidity and temperaturedifference between air and surfaces.When the dew point is reached, water

The most consistent and major problemis the hydrostatic l a t e r a l ressure ofground water which seeks out cracksin concrete or mortar joints.

Elastomeric compounds applied to the

exterior surface of the foundation wallhelp reduce the problem. In addition,drain tile set in gravel around theexterior basement perimeter (Frenchdrain) helps to some degree. Pargingalone is practically ineffectual.Substitution of plastic ilms forparging and many of the so-called"sealants" has, in some cases, beeneffective.

Good drainage starts by keeping rainand melting snow away from thefoundation by proper surface grading.A 1-inch rainfall on an 1,800 square-foot roof will generate about 1,125

gallons of water. Add the water thatfallswithin a few feet of the founda-tion and the drainage from patios,porches, driveways, etc., and thepotential for basement leakage isvery high unless most of the waterhas been removed before it has achance to percolate near the house.

vapor changes froma gas to a liquid.


38/94

Gutters and downspouts are helpful ifthe downspouts direct water far awayfrom the foundation. If not, water isconcentrated in one area, increasingthe probability of leakage at thatpoint. In addition, settling of backfillallows water collection alongside thefoundation walls. By paying carefulattention to surface grading, founda-tion waterproofing is simplified.

Many new drainage boards,panels,fabrics,and plastic mesh productshave been developed recently that areapplied to the exterior foundation wall

and relieve hydrostatic pressure bydraining away water. Some weredeveloped for highway and commercialbuilding construction and have beenproven effective. Some even haveintegral insulation laminated withfilter fabrics and water retardantfacings.

All these products are based on thefact that lateral water pressure is theculprit in most leaky basements. The

major drawback of most systems isthat water which has drained downhas no place to go once it gets there.Drainpipe that simply circles thefoundation perimeter can fill upquickly with water and then eventuallysilt. Water starts backing up thefoundation wall, recreating hydrostaticpressure.

The NAHB/NRC developed a water-proofing method in about 1965 thatstill works. It relieves the hydrostaticpressure by allowing water to drain inthe path of least resistance -- down.The system does not stop at thefooting, however. It provides amethod which keeps the water awayfrom the foundation wall permanently.

The system is used with the pressuretreated wood foundation but wasoriginally developed for use withconcrete and concrete block founda-tions. The system lets water drainunder the basement floor in acontrolled manner where it can eitherdrain into the soil below the slab orinto a dry or wet sump. The systemis described in detail in BasementWater Leakage - Causes, Prevention,and Correction, available from NAHB,15th and M Streets, NW, Washington,DC 20005.

Good supervision and constructionpractices are very important inwaterproofing the foundation.

Cleaning the footing prior to placingthe foundation wall; using care inplacing concrete to prevent entrappedair or aggregate segregation; placingconcrete at least 4 eet per pour;vibrating concrete; using low slumpconcrete; and providing drains forwindow and door wells all help toreduce leakage problems.


39/94


JVAH Foundations

Christian County, Kentucky

Several JVAH sites used innovativeapproaches to foundation constructionthat reduced costs while maintainingstructural integrity. In some cases itwas necessary to provide results ofsoil bearing tests and engineering datato the city building department. Inevery case, less costly foundationsresulted.

Crawl space foundations in ChristianCounty typically are built of onecourse of 12x8x16 lock and twocourses of 8x8x16block. The 12-inchblock serves as a brick ledger. Thebuilder, Norris "Pup" Robertson, usedthree courses of 8x8x16block stackedwithout mortar and bound togetherwith glass fiber reinforced surface


40/94

bonding cement. This reduced theconcrete footing from 20 to 16 incheswide and eliminated 16 inches ofbrick veneer.

Cost savings amounted to $203 perunit for the footing and foundation,and $410 per unit in brick for a totalsavings of $613 per unit.

ical Santa Fe single familyhome oundation consists of an 8x16concrete spread footing and an 8-inchthick, 22-inch high cast-in-placefoundation wall.Mike Chapman, builder, decided tobuild a thickened-edge, monolithicslab which is common in some areasbut not in Santa Fe. This allowed aone-step operation instead of threesteps and saved two days of construc-tion time. Cost savings amounted to$106per unit.

The ypSanta Fe, New Mexico


41/94

Tulsa, Oklahoma

Phoenix, Arizona

Typically, Tulsa single family homesare built with concrete slab-on-gradefoundation/floors. Crawl space homes

with wood floors are rare and usuallymore expensive. Wayne Hood, builder,decided to build a system unique toTulsa -- the underfloor plenum systemon a pressure treated wood foundation.

Instead of using heating and cooling

used as a sealed plenum chamber.Basically, it consists of wood floorconstruction with sealed and insulatedfoundation walls. In the Tulsa JVAHhomes, the underfloor area was usedas a return air plenum with a conven-cases, the underfloor area is used as asupply plenum without duct work.

Information on the system can beobtained from the American PlywoodAssociation, the National ForestProducts Association, the SouthernForest Products Association, and theWestern Wood Products Association.It is being marketed under the namePlenwood.

According to Hood, cost savingsamounted to $1,470 per unit versusconventional slab-on-grade foundationswith overhead heating/cooling ducts.

ducts, the entire under floorspace is

tional up-flow furnace.In most

Knoell Homes conducted soil bearingtests on the site and found the soilhad a bearing capacity of over 3,000psi. Because of this and because ofminimal disturbance to the soil, Knoellreceived a waiver to reduce slabthickness from 3 1/2 to 2 1/2 inchesand to eliminate fill under exteriorconcrete. Savings amounted to $195per unit.


42/94

Valdosta, Georgia


Fairbanks, Alaska

Gary Minchew eliminated reinforcingrods from footings and welded wiremesh from the slab. In addition, heeliminated a metal "key- way" control

joint down the center of each slab,saving $132 per unit in labor andmaterials.

Rex Rogers reduced concrete slab-on-grade thicknesses from a nominal4 inches to a nominal 3 inches, andreduced concrete strength from 2,500psi to 2,000 psi, saving $160per unit.

Pressure treated wood basementfoundations were used in all FairbanksJVAH homes. Tom Webb had beenbuilding wood foundations for severalyears and found no sales resistance.Because of the high concrete costs inFairbanks, the wood foundation wasespecially attractive. It also allowedWebb to extend the building seasonwhich was very important inFairbanks. Cost savings amounted to$1,035 per unit.


43/94

Lincoln, Nebraska Karl Witt used pressure treated woodfoundations in two units but wasreluctant to build more because heanticipated negative market reaction.None occurred.


44/94

WOOD FRAME FLOORS

Most wood frame floors utilize nominal2-inch thick joists placed on a center-bearing beam and covered with sheath-ing. Floor trusses have recentlybecome more popular and post-and-beam crawl space floors have been inuse in some areas for years.

Floor design is based on a number offactors, such as:

Designload

Lumber species, size, and grade

Clear span between supportsFloor sheathing materials and

Fastening techniques

Utilization of fu ll pan capacify oflumberoists can often save between 6and 8 percent of joist framing costs.If allowable spans for joists presentlyused exceed the spans shown on thefloor plan by 1 foot or more, impor-tant savings may be realized bychanging either the joist grade,spacing, or size.

Built-up woodgirders are usually morecost effective and easier to work withthan steel girders.

Floor sheathing adds stiffness to thefloor and, depending on thickness andfastening methods, can result inreducing the size and/or increasingthe spacing of framingmembers.When a plywood subfloor is properlyglued and nailed to the joists, thesubfloor and joist act together as acomposite T-beam and as such willspan a greater distance than if the

subfloor is fastened with nails only.Glue-nailing is also effective inreducing floor squeaks and stiffens thefloor. A single layer tongue-and-groove system is usually less costlythan a separate subfloor and under-layment system.

Bridging or blocking between floorjoists at mid-span has been provenineffectual in almost all cases. Anextensive series of tests conducted bythe NAHBNational Research Center inthe early 1960'sproved that mid-spanbridging adds nothing but cost to mostfloor systems. Major model codes

thickness


45/94

require bridging only in floors withjoists exceeding a depth-to-thicknessratio of 6 to 1 based on nominal

dimensions. In other words, joists upto and including 2x12s do not requiremid-span bridging.

Another common but unnecessarypractice is to doublefloor joists undernonbearing interior partitions, Infact, it is not necessary to locatenonbearing partitions over any joistwhen 5/8-inch or 3/4-inch plywood

partition does not warrant extrasupport. Load-bearing interior wallsusually run perpendicular to joists anddo not require added support. If load-bearing walls run parallel to floorjoists, a supporting girder system isrequired.

Wood frame floors must be anchoredto the foundation to resist wind forcesacting on the structure. In conven-tional construction practice, 2x6 sillplates are attached to the foundationwith anchor bolts, and floor joists aretoe-nailed to the sill plate.

Metal anchor straps are available forembedding in the foundation concreteor mortar that do not require holes inthe sill plate. Such straps are lessexacting and do not interfere withjoist or band joist framing as anchorbolts often do.

Sill plates can be eliminated alto ether

ciently level and accurate. Joists,

however, must rest on a solid surfaceand not over the cores of concreteblock. Anchorage can be provided byanchor straps attached to the joistsand firmly set in foundation concreteor mortar.

Floors built on pressure treated woodfoundationsdo not require separatesill plates or anchoring devices.Joists are toe-nailed directly into thefoundation wall top plate.

subfloor is used. The weight of the

if the top of the foundation is suffi-


46/94

Stairwellframing costs can be reducedin the design stage by positioningstairwell openings parallel to floorjoists. Double joists (trimmers) oneach side of the opening are notnecessary where the header whichthey support is located within 4 feetof the end of the joist spans. Asingle header is generally adequate foropenings up to and including 4 feet inwidth.

The band oist (sometimes called therim or header joist) typically is thesame size as floor joists. The majorfunction of the band joist is to keep

the floor joists vertical. Therefore,if wall studs and floor joists arealigned, a nominal 1-inch thick boardor plywood band is adequate.

In certain cases, the band may beeliminated altogether. When astructural exterior wall sheathing isused, it can extend over the ends ofthe floor joists where the band would

normally be. Joists must be temporar-ily braced until the wall sheathing isapplied.

The typical wood frame floor has twojoists lapping over the center girder,each joist acting independently fromthe other. This system creates pro-blems with plywood sheathing layout,one side of the floor being 1 1/2inches out-of-kilter with the other.

The allowable span of floor joists maybe increased by maintaining continuityover the center bearing -- that is, ifthe joist is continuous rather thanlapped over the girder.

If two joists of unequal length arespliced together so that the spliceoccurs at a point off center, anincrease in stiffness of up to 40percent is possible. This off-center-spliced-joist technique can result inreduced lumber size, increased spacing,or both. In addition, subfloor layoutis greatly simplified.


47/94


JVAH Floors

Tulsa, Oklahoma

However, the added cost of endtrimming and splicing the joists mustbe considered. A Research report

titled Off-Center-Spliced Floor Joists(143-5) s available from NAHB, 15th &M Streets NW, Washington, DC 20005.

Floor trusses are becoming morepopular as alternatives to conventionalwood frame floors. They are usuallymore costly but have the advantage ofgreater spans between supports,

flexibility. There are several differentfloor truss designs, some with openwebs and some with a continuousplywood web. Open web trusses havethe added feature of providing plumb-ing, wiring, and sometimes HVACchases without drilling or cutting.

The major disadvantage of single-spanfloor trusses is the height of thetrusses. In order to span greaterdistances, the truss must be muchdeeper than conventional 2x framing.This adds extra costs to sheathing,siding, stairs, etc. These, plus theextra cost of the floor itself, shouldbe analyzed versus the value of theclear span.

thereby creating greater floorplan

Innovative floor framing methods wereused on several JVAH sites. Somewere unique while others were known

methods not normally used in the localarea.

As discussed in the Foundationsection, Wayne Hood built thePlenwood system in his demonstrationhomes. The wood framefloorportionof the system consisted of 2x8 floorjoists spaced 24 inches on centerwith glue-nailed 3/4-inch plywood.


48/94

Lacey,Washington

John Phillips constructed one of themost innovative wood frame floors inthe demonstration. Typically, in theLacey area, the foundation/ floorsystem consists of a conventionalspread footing, a cast-in-placeconcrete foundation wall, a post-and-beam center bearing girder, 2x10joistsspaced 16 inches on center, and a twolayer sheathing/underlayment system.

Phillips designed and built a systemthat used 2x6s,spaced 24 inches oncenter, spanning about 8 feet betweenpost-and-beam supports. Band joistswere eliminated. Floor framing didnot come into contact with theperimeter foundation at all. The firstinterior support girder was placedabout 4 eet from the foundation walland the joists cantilevered about 2feet toward the foundation.


49/94

Christian County,Kentucky

The 2-foot gaps at the ends of thefloor joists and the 2-foot spacingwhere the joists are parallel to thefoundation were easily spanned with3/4-inch tongue-and-groove glue-nailedwaferboard. Floor construction costswere reduced by an average of $852when compared to the conventionalfloor.

Pup Robertson also built an innovativefloor system that saved $295perhouse. Instead of the conventional2x8, 16-inch on-center joists over asingle center girder, he used two boxgirders spaced about 8 feet on centerand 2x6 joists at 24 inches on center.He used 3/4-inch glue-nailed T&G

tional 1/2-inch underlayment.plywood instead ofhe more conven-


50/94


51/94

WALLS AND PARTITIONS

The key to economical wall and parti-tion construction is preplanning toeliminate unnecessary materials andlabor. Carpenters usually find extramaterial is needed here and there toaccommodate doors and windows.

They may also follow traditionaltraining by adding studs wherepartitions intersect exterior walls,blocking at mid-height of walls,double studs and headers at openingsin nonbearing walls, and similarpractices. Each of these excessivematerial uses is avoidable throughproper attention in the planningstage. They add significantly o ostwithout benefit to the home buyer.

Cost savings will be greatest when theoverall out-to-out dimensions of thehouse and the location of wallopenings coincide with a module of 2

feet. This provides maximum use ofmaterials that are available in 2-foot

increments and reduces scrap andwaste.

An important side benefit to preplan-ning will be education of the car-pentry crew. When the crew has builta number of units in accordance withcost saving techniques presented inthis section, less detailed instructionsand fewer on-site modifications will berequired.

Tilt-up wall construction continues tobe the preferred method for reducinglabor and material costs. Assemblingwall sections to the greatest extentpossible prior to erection is beneficialsince materials do not have to beheld up while they are being fastened.This includes framing and sheathing (ifused), as well as siding, windows andexterior trim. Fabrication can bedone on a shop table or right on the

floor deck. Use end nailing, not toe-nailing, to fasten plates to studs.


52/94

OVE Techniques Engineering analysis and testing haveresulted in widespread acceptance ofmany changes in traditional wallframing techniques. Many of theseOVE (Optimum Value Engineered)techniques were developed and testedby NAHB National Research Center.

Building 7'6" high walls instead of 8'0saves approximately one course ofsiding or two courses of brick, 6percent of wall insulation, 3 percentof painting labor and material, onetread and riser on a flight of stairs,and 9 to 12 inches of stair landingspace.

A lower ceiling height also increasesthe structural capacity of studs actingas a column. The savings in material

labor to cut 6 inches from the top ofthe gypsum wallboard panels.

Placing studs 24 inches on center,instead of 16 inches, reduces framinglabor and material. The 24-inch on-center spacingis permitted in most

the second story of two storyconstruction. Use of 24 inch spacingsaves nearly a third of the regularstudding.

Single top plates can be used whenstuds and trusses are in line on 24-inch centers so that the weight of thetruss bears directly on the stud.Special connectors to splice joints inthe top plate or to tie corners are notrequired because the floor or roofsystem attached to the top plateserves this function, This techniqueeliminates one-third of the platematerial.

When studs sit directly over floorjoists, the bottom plate is used onlyto facilitate alignment of the studs,and to provide a nailing base forwallboard, sheathing and baseboard,and not to carry weight from the stud

and labor more than of Het the extra

areas oPhe country for one story and


53/94

to the joist. Since the bottom platedoesn't have to be as strong, a 1x4 issufficient.

Because the maximum load on thecorner studs in an exterior wall isone-half or less than the load on aregular stud, two-stud corners aremore than adequate structurally. Thethird stud in the normal three-studcorner post serves only to back up theinterior finish, and can be eliminated.Metal drywall clips or wood blocks canbe used to backup the wallboard.

Similarly, partition posts built into the

exterior wall for attachment ofinterior partitions can be eliminated.The partition can be nailed to a mid-height wall block, and wood blocks ordrywall clips can be used to backupthe wallboard.

Ceiling nailers can be replaced withdrywall clips. Since they secure theceiling gypsum board to the walls,the clips offer the additional advan-

gypsum board from separating. Mid-height "firestop" wall blocking can beeliminated. Wall plates, floor sheath-ing, and insulation psufficient

wall to minimize fire spread, and theblocking is not required for structuralbracing.

Headers or lintels, and jack (jamb)studs which support them are requiredonly where loads must be carried tothe sides of window and door open-ings, If the loads don't exist, or ifother members, such as roof trusses,joists, joist bands, large areas ofstructural sheathing, or second storyheaders carry all or part of the loadsacross the openings, headers can beeliminated or downsized.

Openings in nonbearing walk can havesingle 2x4's on each side to whichwindows and doors are fastened.

tage ofkeeping the ceiling and wall

constriction of air flowwithin the


54/94


55/94


JVAH Walls and Partitions


Most JVAH sites used some aspects ofOptimum Value Engineered wallsystems to minimize costs. The mostcommonly used techniques were in-lineframing with 24-inch stud spacing,single top-plates, 1x4 bottom plates,two-stud outside corners, metaldrywall clips instead of wall andceiling nailers, and elimination of

headers and jack studs in nonbearingwalls.

Besides using OVE techniques whichsaved $448per unit, Pup Robertsonsaved 3,000 bricks per house bystarting the brick at the bottom ofthe wood floor instead of below grade,eliminating gable brick and reducingthe wall height to 7'6"; moreover,since each house required less brick

than normal, he was often able tobuy odd-lot quantities at substantialsavings. These techniques saved$1,685per unit on brick veneer.


56/94

Fairbanks, Alaska

White Marsh,Maryland

Tom Webb used 2x6 exterior walls and2x4 interior partitions on 24-inchcenters. Costs were reduced by over$1,200 per unit.

Ryland Homes has been using efficientconstruction techniques for years. Forthe JVAH demonstration, modularhousing units were used with 24-inchon-center wall framing, two-studcorners, and no headers in nonbearingwalls. Costs were reduced by $850when compared with more typicallyused 16-inch on-center framing.


57/94

Charlotte, North Carolina

Lacey, Washington

John Crosland had already adoptedmost of the OVE techniques. Inaddition to 24-inch on-center wall

framing, he also used sections ofplywood truss floor joists for windowand door headers. This no t only wasless expensive than ical built-up

for insulation.wood headers, but alsoprovided space

John Phillips used almost all of theOVE framing techniques in the demon-stration homes. He also had a veryinnovative floor system (see floorframing section) and used single-layerplywood siding without a separatesheathing. He saved almost $1,200 perunit.


58/94


59/94

were about the same as conventional2x4,16-inch on-center costs. But inorder to get the same insulation R-value (R-19) with a 2x4 wall, costswould have been $460 per unit higher.Interior partition costs were reduced

Crittenden County, Arkansas By using OVE techniques, Rex Rogerssaved $495 per unit even though he


60/94

Valdosta, Georgia

Tulsa, Oklahoma

Burlington, Vermont

Mesa County, Colorado

Gary Minchew has long been a propo-nent of the OVE framing system. Hisdetailed cost recording system pro-

vided a unique breakdown of wherecosts were saved with OVE. Totalreduction amounted to over $1,200 perunit when compared with conventionalconstruction in the area.

Wayne Hood used 24-inch on-centerframing with two-stud corners on allnonbearing walls and partitions, saving$250 per unit.

Bill Hauke had been using OVEtechniques in Vermont for years. Heestimated that these methods savedhim over $450 per unit in the JVAHIn-fill Demonstration Project.

Roger Ladd used two-stud corners andsingle-layer plywood siding on 16-inches on-center exterior walls.

Partitions and common walls wereframed 24 inches on center.


61/94

FIREWALLS

Growing pressures on land availabilityand housing affordability are resultingin an increase in demand for attachedhomes. Zero-lot-line configurations allowed.are becoming more popular fordetached homes because of moreinnovative use of small lots. Theprincipal added code consideration forattached and zero-lot-line homes isthe requirement for fire barriers.

Requirements of the major model codesare not always clear and are often

subject to local interpretation and/oramendment. It is important to under-stand that all major model codes havean "Alternate Materials and S stems"

have the discretion to approvealternate construction. Appropriatedocumentation is, of course, usuallynecessary.

To be acceptable, firewall construc-tions must be rated by a recognizedtesting laboratory in accordance with

ASTM E119, Standard Methods of FireTests of Building Constructions andMaterials. Many different one- andtwo-hour wall constructions have beenapproved and are listed in literatureavailable from the Gypsum Association,1603 Orrington Avenue, Evanston, IL60201; the National Concrete MasonryAssociation, P. O. Box 781, Herndon,VA 22070; and other industryassociations and productmanufacturers.

For zero-lot-line homes, each unitmust have an independent one-hourfire-resistive rating. The StandardCode Southern) Uniform BuildingCode ICBO), and the One and TwoFamily Dwelling Code (CABO), allrequire one-hour ratings for homesbuilt less than 3 feet from theproperty line. The Basic/NationalCode (BOCA) requires a one-hourrating on exterior walls less than 6feet fromthe property line. None of

the codes permit unprotected openingsthrough a firewall. Normal electrical,plumbing, and ductwork are generally

The most common one-hour firewall isof wood frame construction with 5 /8 -inch type X gypsum wallboard or

sum sheathing attached to eachsidewith 6d coated drywall nails 7inches on center. Joists are requiredto be staggered at least 24 inches oncenter on each side.

For attached homes, a two-hourfirewall is required, either as twoseparate one-hour walls or as acommon two-hour wall at the propertyline. Check your local Code. Thetwo-hour common wall typically builtis a single wood frame wall with twolayers of 5/8-inch type X gypsumwallboard on each side or concreteblock. Two-hour walls typically haverestrictions on electrical wiring,plumbing, and ductwork within the

wall.In addition to the firewall, someprovision is required to block thespread of fire to the roof of anadjoining unit. For zero-lot-linedetached homes, codes are somewhatvague because there is no adjoiningroof.

In addition to confusing major modelcode firewall and roof treatments,some local codes require that firewallsbe built of masonry construction.This requirement is prohibitive forfactory-built construction.

As mentioned, three of the four modelcodes require a firewall if within 3feet of the property line. The othercode, BOCA, requires a firewall ifwithin 6 feet of the line. If a homeis built 37 inches from the propertyline (73 inches under BOCA), nofirewall is needed.

section and that local code officials


62/94



If an easement for use of that narrowstrip of land is assigned permanentlyto the house next door, a zero-lot-

line effect is obtained without cost ofa firewall or roof parapet. It will beworthwhile to check local interpreta-tion of firewall/roof treatmentrequirements prior to construction.

Since the major model codes aredifficult to interpret and have notseriously addressed detached zero-lot-line homes in many cases, a completereview and rewrite of all codes shouldbe undertaken.

Three JVAH sites, (Lacey, WA,Everett, WA, and Santa Fe, NM),all

built under UBC, ran into the problemof firewall and roof treatmentrequirements.

In Santa Fe, the normal city require-ment is a masonry firewall betweenattached garages, including a parapetabove the wall. The builder obtainedthe Fire Resistance Design Manualfrom the GypsumAssociation whichshows wood frame firewalls.

In addition, he pointed to the 1,000square foot per floor exception forroof fire treatment in UBC. Theseconvinced the city that a commontwo-hour wood-framed firewall withno parapet or roof treatment wasadequate.


63/94

Lacey, Washington

Everett, Washington

In Lacey, the city required either aparapet extending 30 inches above theroof or that all framing elements(trusses, wall plates, studs, etc.)within 5 feet of the two-hourseparation wall be of one-hour fireresistance construction.

The builder, John Phillips; pointed outthat none of the other major modelcodes had this requirement and thatfire-resistive sheathing, installed atleast 4 feet from the wall, providesadequate fire safety according tobuilding code experts. The cityaccepted his documentation whichresulted in substantial cost savings.

In Everett, zero-lot-line homes werebuilt with one-hour fire walls. Thecity accepted the builders documenta-tion that type X fire-rated gypsumboard under roof sheathing, within 4feet of firewall was adequate tocomply with the intent of the code.


64/94

ROOF FRAMING

The standard roof truss has becomethe most common and most cost-effective method of roof framing.Light-weight trusses are the mosthighly engineered component in newhome construction and form the basisof a very efficient roof system. Theyare easy to install and adapt to manybasic designs. Therefore, if cost isthe primary consideration, standardroo trusses are recommended.

eliminated, leaving the truss or raftertails exposed. Blocking betweentrusses or rafters and a 1x6 fasciaboard are the only finish itemsneeded. If soffit venting is needed,screening between trusses or rafterscan be used instead of blocking.

Three-eights-inchplywood roofsheathing with metal plyclips is anacceptable alternative to l/2-inchplywood.

P

The "in-line" framing concept dis-cussed in the House and Lot Designsection of this manual works very wellwith roof trusses. That is, the 24-inch on-center roof trusses align withthe 24-inch on-center wall studs whichin turn align with the 24-inch on-center floor joists. The key to thisconsistent alignment is to start alllayout from thesame corner.

Simplification of roof overhang andtrim details, consistent with designand function, provides opportunitiesfor cost reduction. For example, therake overhang is essential1 nonfunc-tional on a gable end roof. A simplefascia board at the siding/roofjunction serves to cover the roughedge of the siding and concealinaccuracies of fit. Several of thenation's largest builders use thisdetail on al l their production homes.

the frontan rear of he house.TheyRoof overhangs are desirable for mostdesigns and provide rain protection for

also can provide summer shading forsome windows. When an overhang isused, an inexpensive "open" soffit willeliminate much of the cost of thetraditional cornice. All trim details onthe underside of the overhang may be


65/94


Lincoln, Nebraska

Everett, Washington

Mesa County, Colorado

Many of the demonstration projectsused trusses and several used thesimplified trim details described above.However, several projects also used

provide more open space in relativelysmall homes. In some houses thevaulted ceilings provided lofts andexpandable space.

vaulted ceiling rafter framing to

Karl Witt used vaulted ceilings withclerestory windows in the living areaof his homes. This provided a degreeof passive solar heating and naturallighting.

Vaulted ceilings with clerestorywindows and open soffit overhangswere used in Everett.

Instead of the more typical 1/2-inchplywood roof sheathing, Roger Laddused 3/8-inch plywood with metalplyclips.


66/94

PLUMB IN G

An excellent opportunity exists toreduce construction costs throughinnovative plumbing. But plumbing isalso one of the more difficult areasto get innovations adopted. In spiteof the fact that present modelplumbing codes are updated periodi-cally, the process is lengthy anduncertain, so none of the model codesreflect current state-of-the-art.

In addition, comprehensive model

plumbing codes cover all types ofbuildings and are overly complex fordealing with relatively simple re-quirements of single family dwellings.

The four major model plumbing codesare the BOCA Basic Plumbing Code,the SBCC Standard Plumbing: Code, theNAPHCC National Standard PlumbingCode and the IAMPO/ICBO UniformPlumbing: Code.

Many local jurisdictions use one of

the model codes with their own modi-

fications. In almost all cases, localmodifications are more restrictive inmaterial and design than the parentmodel code.

Confronted with these facts, the NAHBNational Research Center has compileda state-of-the-art manual for residen-tial plumbing. This effort, sponsoredby NAHB and HUD, resulted inResidential Plumbing: Guidelines whichcontains all requirements to assure asafe, functional, durable, and cost-effective residential plumbing system.NAHB submitted proposed code changesto the Council of American BuildingOfficials (CABO) in 1984,and theproposed changes were adopted inJanuary, 1986.

Substantial changes were made in someareas of the code. Following is asynopsis of the more relevant changesthat affect the installed cost of

plumbing.


67/94

Drains The load on the drain, waste, andventing (DWV) system is determined bydrainage ixture unit (d.f.u.) values.

This is a measure of the probabledischarge into the drainage system byvarious types of plumbing fixtures andis used to size DWV piping systems.

The newly adopted d.f.u. values are,in every case, less than those in theold CABOcode. The old values arebasically the same as those used inthe other major model codes.

The new CABOcode includes d.f.u.values for plumbing fixture groupings.

These values are less than the sum ofindividual fixture units, whichrecognizes the fact that d.f.u. valuesare not additive when the probabilityof simultaneous use is very, very low.

The new CABO code allows 75 footspacing of cleanouts versus 50 footspacing in the old code. This isconsistent with standard availablesnake lengths.

The new CAI30 code allows smallersize traps and trap arms for somefixtures. Below-grade drain pipeminimums were reduced from 2 to1 1/2 inches in diameter because ofpower driven cleanout equipmentcapabilities.

In practice, large diameter drain pipeis often perceived to be desirable.However, with the lower dischargerates of modern residential fixturesmanufactured to water conservingstandards, large diameter drains havevery low flow rates which promotedeposition of solids.

Smaller diameter ipe with higher flowrates actually provides improvedtransport characteristics. This is aclassical case where bigger is notnecessarily better and where tradi-tional thought is outdated.


68/94

Vent Systems

The new CABO code allows anincrease in maximum trap arm lengths.This provides a degree of architecturalflexibility such as the location ofkitchen sinks under windows.

The purpose of the venting system isto maintain atmospheric pressurewithin the DWV system and to provideventing of gasses by circulating airthroughout the system. At low flowrates, characteristic of residentialconstruction, vent pipes need only be

of small diameter. In addition, ventsneed not penetrate the roof. Rather,vents can extend through an exteriorwall or roof overhang and terminatedownward.

According to the new CABO code, "Acommon vent may be used for twowaste fixtures connecting at differentlevels in the stack but within thesame branch interval, provided thevertical drain is one pi e diameter

but in no case smaller than the lowerfixture drain. The vertical pipingbetween fixture connections servesas a wet vent for the lower fixture."(Section P-2207.7.1, One and TwoFamily Dwelling Code).

Tne CABO code also states, "Stackventing, with certain preconditionsrelating to drainage loads and vent-ings, fitting types and sizes, andplacement of connections, shall be

permitted as a system that allowsFixtures and fixture group to beindependently connected to a soil orwaste stack without individual fixtureventing." (Section P-2207.8, One andTwo Family Dwelling Code).

larger than the upper fixture drain,


69/94

Water Serviceand Distribution

The significance of these paragraphscannot be overlooked inasmuch as thetotal cost of plumbing DWV in anaverage home can be reduced substan-tially. When combined with otherDWV innovative practices, total costshave been reduced by as much as$400,depending on which code wasused as the comparison.

Because of this (and the fact that thetechniques have been proven for manyyears to be safe and reliable), it Willbe well worth while for builders topush for adoption of the plumbingsection of the CABOcode.

As with DWV piping, water servicerequirements in the CABO code havebeen changed significantly toward costreduction and efficiency. Healthstandards have been maintained in allcases.


70/94


71/94

Other Cost Saving Techniques

The CABO code also recognizes thedifferent flow rates of different pipematerials and the w.s.f.u. values varyaccordingly. Therefore, supply pipeoften can be reduced in size dependingon the number and type of fixtures.

The significance of the new CABO Oneand Two Family Dwelling Code cannotbe overemphasized. Studies haveshown a total cost reduction in supplypiping of as much as 24 percent evenwhen the same piping material is used.

For more information on the innova-tions discussed herein, write theCouncil of American Building Officials,5203 Leesburg Pike, Suite 708, FallsChurch, VA 22041.

There are methods to reduce plumbingcosts regardless of code restrictions.Some may require negotiating with theplumbing subcontractor to get full

benefit, others may require marketevaluation to determine consumeracceptability.

Cluster theplumbing. This cost-savingdesign principle is to arrange plumbinggroupings back-to-back in a commonwall and to shorten distances of otherplumbing runs as much as possible. Inmultiple-story buildings, fixturesshould be located over each other tominimize DWV and supply piping.Savings can amount to as much as 10percent. Plumbing subcontractorsoften bid on a "per fixture" basis sothe value of clustered plumbing maynot be passed on without negotiation.

Whitelumbing fixtures are lessexpensive than colored fixtures. Asavings of $40 to $75 per bath can berealized. From a consumer standpoint,any accent or decorating color can beused with white fixtures.


72/94

C o d e r iberglass bathing modules.They often are less expensive thanother bathtub/shower materials.

Wall hung lavatories can reduce costsalthough vanities have becomestandard. Wall hung units may be amarketing problem, but they should beconsidered, especially in powder roomsand/or second bathrooms.

Size water heaters according tointended use. Smaller homes intendedfor small families do not need largewater heaters. Thirty-gallon gas or30- to 40-gallon electric water heatersare generally adequate. Also, waterheaters with a five-year warranty costabout $20less than units with a ten-year warranty. This reflects anadditional five-year insurance policy,not the basic construction of thewater heater.

Consider polybutylene supply piping.This material is flexible and, there-fore, requires only about 1/3 thenumber of fittings as rigid pipematerials. It normally costs much

less to install and has some ad-vantages in flow characteristics.Field studies have showncost savingsof between 30 and 50 percent.


73/94


Portland, Oregon



The Portland demonstration subdivisionwas arranged in clusters of fourdetached units. The city allowed one1 1/2-inch PVC water line to runfrom the main to each cluster and3/4-inch PVC from there to each unit.This was instead of one 1-inch linefrom the main to each unit. Costsavings amounted to $32 per unit.

Rough plumbing was installed in atrough above the slab so the plumberwould make only one site visit. Allplumbing was clustered to reduce DWVand supplypipe lengths. A standard-ized DWVlumbing "tree was used;therefore, much of the DWV systemcould be prefabricated. The plumbingwall was prefabricated with supplypipe and DWV installed. Polybutyleneplastic pipe was used instead ofcopper. Total plumbing cost savingsaveraged $182 per unit.

Polybutylene supply pipe, fiberglassbathtubs, and cultured marblelavatory/vanity tops were usedinstead of copper pipe, cast ironbathtubs with ceramic tile surrounds,

hardboard vanity tops, and ceramiclavatories. Total cost savingsamounted to $367per unit.


74/94

Tulsa, Oklahoma

Phoenix, Arizona

Valdosta, Georgia


Burlington, Vermont

Use of polybutylene supply pipereduced costs by about $100per unit.

Polybutylene supply pipe was usedinstead of copper, reducing costs by$65 per unit.

Gary Minchew redesigned his homes tocluster plumbing in a central area,thus reducing DWV and supply piping.Because the plumber would not reducehis total bid, Minchew hired his ownmaster plumber and found that hiscosts were reduced by an average of$400 per house.

The builder used CPVC rigid plasticpipe for hot and cold water serviceversus copper, thereby reducing costsby about $105 per unit.

Polybutylene water and PVC DWV pipewas used. Reduced size vents and onewater main per four units reduced costs.


75/94


76/94


Phoenix, Arizona

Santa Fe, New M exico

Homes were designed with duplexoutlets located at points of probableuse rather than the arbitrary 12 footminimum. About three outlets perhouse were saved. Because extracare was taken not to eliminateuseful outlets nor to endanger safetyof the occupants, the city buildingdepartment allowed the variance.

In addition, because the units weresmall and expansion possibilities few,service entrance panels were reducedfrom 200 to 100 am . Total electricalcosts were reduced by$108 per unit.

As in Phoenix, the builder wasrequired to comply with all electricalcode provisions except the arbitraryspacing of outlets. A well-thought-outlayout was submitted based on logicaluse patterns along with the rationalefor outlet locations.

In addition, garage ground-faultinterrupters were loop-wired tobathroom outlets, thereby eliminatingground-fault interrupters in bathrooms.Bathroom exhaust fans were eliminated

along with overhead light fixtures.Total electrical savings amounted to$320 per unit.


77/94

HEATING, VENTILATION, AND AIR CONDITIONING

Because HVAC system design iscomplex, judgement on system type,size, and location of ducts is oftenleft to the expert -- the HVACsubcontractor. But the builder shouldunderstand some basic facts to insurethat the most efficient, cost-effectivesystem available is being installed.

Select the most appropriate economicalsystem according to home design, localclimate, fuel availability, and market

preference. If a ducted system is tobe used, a concise guide is availablefrom the National Association of HomeBuilders, 15th & M Streets, NW,Washington, DC 20005. TitledResidential Duct Systems, this guidedescribes the most efficient ductmethods according to fuel, type ofequipment, operating efficiencies, andrelative cost.

Design starts with accurate heat losscalculations (and heat gain forcooling). This is the only real basisfor selecting equipment and designingthe system. Too often equipment isselected based on past experience andjudgement.

But, since each home design is unique,the HVAC system should be tailormade for that home. Guidelines onhow calculations are made arepresented in the Residential DuctSystems manual mentioned above as

well as in the Insulation Manual forHomes and Apartments, also availablefrom NAHB. 20036.

The standard calculation procedureused in the HVAC trade is in ManualJ, Load Calculation for ResidentialWinter and Summer Air Conditioningavailable from Air ConditioningContractors of America, 1228 - 17thStreet, NW, Washington, DC 20036.

Avoid the tendency to oversize W A Cequipment. Some believe that if acertain size equipment is adequatebased on roper calculations, a size

larger will be even more desirable.Since the incremental cost of upsizingappears not too excessive, it is tempt-ing to oversize. However, equipmentbased on sound heat loss-gain calcula-tions is almost always more efficientand uniform in heating and coolingthan oversized units. Also, be awareof unit efficiency.

For each 1/2-ton heat pump or airconditioning reduction, equipment andduct costs can be reduced by about

$275. Wiring costs may also be reducedsince a lighter circuit may be possible.

Downsized or redesigned duct systemswill be possible in energy-efficienthomes where HVAC equipment issmaller. In addition, the system willperform better since proper velocityand air flowwill be maintained.Another standard guide for residentialduct design is Manual D -Duct Designfor Residential Winter and Summer AirConditioning, from the Air

Conditioning Contractors of America,1228 17th Street, NW, Washington, DC

P


78/94

In small, single-story homes with acentral hall that abuts all living areas,consider using a dropped-hall ceilingplenum system. In this system, thehall ceiling and walls are drywalled asusual. Thenanother ceiling, dropped6 inches to 8 inches below the con-ventional ceiling, is framed anddrywalled, thus providing a plenum forair distribution.

High inside wall registers to eachadjoining room are connected to theplenum by a short sheet metal bootthrough the wall. Although thesystem described has worked well inmany installations, some local inspec-tors insist on sheet metal ductswithin the ceiling cavity. If so, thesystem is still more cost effectivethan most.

The CABO One and Two FamilyDwelling Code permits such "gypsumducts" up to 125 degrees F., whichwould accommodate low outputtemperature equipment such as mostheat pumps or electric furnaces.Fossil fueled equipment generallyexceed this temperature limit.

Radial duct systems are often thesimplest duct systems to install.Branch ducts connect directly to theequipment plenum without trunks.Radial systems are typically installedwhere it is not necessary to concealthe duct work and where the equip-ment is centrally located. The basicsimplicity of the system provides costsavings through reduced materials andless labor.


79/94

In smaller, well-insulated homes wherecentral air conditioning is not re-quired, electric baseboard heat withindividual room thermostats offerssignificant construction cost savings,and depending on comparative fuelcosts and availability, may offeroperating cost savings because of theability to "zone" heat the house.

One very innovative heating/coolingsystem that has enjoyed some regional

success is the underfloor heating/cool-ing plenum, being marketed by thewood industry under the name"Plenwood." Instead of using heatingand cooling ducts, the entire under-floor space is used as a sealed-plenum chamber to distribute warmor cool air to floor registers in therooms above.

A downflow forced air heating and/orcooling unit maintains slight airpressure in the plenum, assuringuniform distribution of conditioned airthroughout the building with few orno supply ducts. Studies have shownthat the initial costs of the Plenwoodsystem are typically about 10 percentless than conventional ducted systems.For more information on the PlenwoodSystem, write the American PlywoodAssociation, P.O. Box 11700, Tacoma,

WA 98411.

Non-ducted range hoods cost $20 to$40 less, eliminate a schedulingproblem, and are more energy-efficientthan ducted systems. However, humid-ity control and indoor air qualityshould be considered.


80/94


Several of the JVAH builders usedinnovative HVAC systems to reduce

costs. In SantaFe

andPhoenix,

bathroom ventilation fans wereeliminated, savin about $150 per unit

In Crittenden County, Arkansas, thebuilder used the ductless droppedceiling approach to air distribution inhomes with central air conditioning.

In Christian County,Kentucky, aradial duct system was used insteadof one large trunk line throughoutthe center of the crawl space withlateral ducts. This system saved anaverage of $125 per house.

The most innovative HVAC systembuilt in the JVAH program was inTulsa, Oklahoma, where the Plenwoodsystem described earlier was installed.Wayne Hood used the underfloor areaas a ductless return air plenum (SeeFootings and Foundation Section) witha pressure treated wood foundation.Hood estimated that foundation, floorand heating cooling costs were reduced

in ventilation andelectrical wiring.

by a total of$1,470 per unit.


81/94

BUSINESS/MARKETING

An important means of achievingaffordable housing is by running anefficient business. Good businessplanning, organization, and controlare essential to keeping costs as lowas possible.

affordable residential construction vol2

Documents