Building Planning…

Egress & Core strategies

Example, multi-tenant office bulding

Key issues Return on investment Clear circulation/wayfinding Maximize value of perimeter glass/views Allow for street level retail High net to gross ratio (what’s that?)

Net: What you can rent… Face of wall to face of wall

The higher the net assignable square footage (NASF) the higher the income

Also used to compare efficiency between concepts

Gross: everything else Stairways Lobby Toilets Custodial Mechanical/electrical Wall thicknesses Amenity spaces

(workout/atrium…)

Some common net to gross ratios

Administrative buildings 67/33

Auditorium buildings 70/30 Courthouse 61/39 Hospital 55/45 Office buidling 75/25 (80/20

common) Science building 60/40 Warehouse 93/7

The larger number is usually the net…those functions that are the reason to build the building

The smaller number is the net…those functions that serve the above.

… even star architects watch it very closely between schemes

Public/employee sequence dominates…but doesn’t locate

elevators

Lobby/Reception/directory/security

Entry/vestibule

retailretail

Double loaded lobby allows two retail tenants

Single loaded would allow one larger tenant

Challenge might be identity

Other core responsibilities

Besides housing egress, access, toilets and HVAC, cores often act as the primary space definition elements on a floor.

They also are often used for lateral bracing of the structural frame, with walls reinforced to be shear diaphragms or with “X” bracing or chevron bracing concealed within their enclosing walls

Core location…always center?

Willis Tower, Chicago

53,000 net rentable s.f.

Empire State Designed for

Rapid-Building• … 2,768,591s.f. in 410

days?6,752 s.f. per day!

• Standard Bay sizes• Standard Mullion

spacing• Stone sizes fit to

milling equipment• Steel sizes fit to

transport/lifting equipment

Setbacks change

floor plates• Meeting zoning

required stepping back the building, reducing the number of repeated floors

• Upper floors consumed by elevators (73 total)

End Core location responds to local conditions…view, climate…

What looks problematic?

Lever House, NYC, Gordon Bunshaft, 1952

Multi Core placement for large floor dimensions (<300’)

Sendai Mediateque, Ito atomizes the core

So…if its an office building…

Alley

Main Street

Easy

Str

eet

Adjacentstructure

High-value corner retail

Lower-value

streetfront retail

…but the tail can’t wag the dog

The corner retail will produce higher rental costs, but will it compromise the 15 floors of building above it?

The street-front retail will tolerate more spatial disruption due to its lower rents, but how much can we intrude on it?

Time to consider the cores

coreS?...not just one? Every floor will need

Elevator access 2 means of egress (elevators won’t count) Toilets for each gender Some electrical/telecom space Some space for ventilation/hvac

Could be a shaft Could be a fan room

A midrise building core

Will Paton, final study F2011

men

women

egress egressmechelevators

Basic organization forms

You might generate alternatives in more than one

Or the site, or inner organization of the clients enterprise might hint at which is most appropriate

Ultimately these begin to form a backbone, an armature to hang the building infrastructure upon.

Deploying infrastructure Building planning is a design stage where the

infrastructure elements of the building are located in ways that meet the appropriate codes and delineate space for the primary functions of the building

Put these somewhere…in a way that makes the primary functions better

Elevators Stairways Entry/Lobby Toilets Mechanical/Systems spaces Circulation elements, corridors, egress paths

Know the land

From a building planning perspective, this might mean answering these questions Where do we enter? Where should trash and deliveries go? Does the building have to be phased or planned

for an addition? Which orientation or orientations have the

highest value? Which have the lowest?

Know a few things about the code

…how to get out in a fire …how to arrange exits …how big they have to be …

Egress Promoter P.T. Barnum is said to have charged people 25

cents to enter a darkened room and “See the Egress.” Once in the darkened room, the people could only see a

dim light over a door with a sign on it saying “This way to the Egress.”

Upon opening the door and walking through they found themselves on the street!

Egress is the term applied to the various means (corridors, stair enclosures, stairs) to be used as a means of escape in the event of a fire or other disaster in the building.

Some key IBC Definitions Area of Refuge: Area where persons unable to use

stairways can remain temporarily to await instructions or assistance during emergencies

Corridor: An enclosed exit access component that defines and provides a path of egress travel to an exit.

Exit: That portion of a means of egress system which is separated from other interior spaces of a building by fire resistance rated construction and opening protectives as required to provide a protected path of egress travel between the exit access to the exit discharge including exit doors, exit enclosures, exit passageways

How Many People? The IBC offers the choice of two processes for

determining the number of people (occupants) in the building. The first method is to determine the actual number of people

in the space. This is easier to do in a building with fixed seating

(auditorium) than in say an open office space where, the density varies over time.

The second method is to refer to the Maximum Floor Area per Occupant table, find your use type, divide the number of gross square feet per occupant in the table into your project’s gross square footage to arrive at the number of occupants in the building, or per floor.

Occupant load table …excerpted

Occupancy Floor Area in Square Feetper occupant

Assembly without fixedseats Concentrated (chairs) Standing space Unconcentrated (tables and chairs)

7 net5 net15 net

Business Areas 100 grossDormitories 50 grossEducational Classroom Area Vocational Areas (shops)

20 net50 net

Library Reading Area Stack Area

50 net100 gross

So our BusinessOccupancy would take the program area (40,000 s.f.) and divide it by 100 s.f. to determine we have 400 occupants

Egress convergence

As the occupants from a floor above exit through lower floors, they don’t impact the exit size for the floor the pass through, but the exit size cannot get smaller.

But when exits converge at a floor, like the ground floor where they leave the building, the occupant load for the ground floor must take into account the occupant load of the floor immediately above.

First floor, 10,000 s.f. = 100 occ + 100 from second, 200 occupants

100

100 + 100

100

100

How wide does that make the exit?

The IBC reads “The total width of the means of egress in inches shall not be less than the total occupant load served multiplied by” .3 for stairs in unsprinkled buildings .2 for corridors, other egress components in unsprinkled buildings

.2 for stairs in sprinkled buildings .15 for other components in sprinkled buildings

So our top floor stair in our unsprinkled example could be no less than 100 x .3 or 30 inches…not nearly wide enough to meet minimums of the IBC or ADA

So the code continues to read “nor less than specified elsewhere in this code” so it let’s itself out of an apparent contradiction

Stairways Two required Fully enclosed with 2

hour fire rated construction

Minimum stair width 48”

Max stair width without intermediate railing = 5’ Minimum headroom 80” from nosing line

Max height between landings = 12’-0”Minimum depth

Of Landing, 48”

Max riser 7”Min tread 11”Within 3/8 of same dimension for all steps

Max intrusion of door on landing = 7”

Stairways…cont’d

Handrail height 34” - 38”

Handrails required both sides. 1-1/4 to 2” dia, 1-1/2” from wall (clear)

Handrails must extend 12” beyond top riser, and one tread (11”min) beyond bottom tread

11”12”

2 exit spacing

Exits cannot be closer than 1/2 the maximum diagonal distance of the floor plate80 feet

60 feet

Diagonal is 100’ long so 1/2 diagonal is 50 feet

2 exit spacing

• So in this example, the exit stairs could not be placed closer than 50 feet apart

• Maximum travel distances would be for this type ‘B’ building– 200 feet without

sprinklers– 250 feet with sprinklers

• What would be the maximum stair spacing in a sprinkled type ‘B’ building?

80 feet

60 feet

So stair entries must be 50 feet apart, minimum

50 feet

Dead End Corridors

A corridor not ending in an exit is considered a dead end corridor

Dead end corridors are limited to 20 feet in length in most occupancies.

In occupancy group B with a sprinkled building, the dead end can be extended to 50 feet long.

20 feetDead End

Ends in an exitNot a dead end

On your way to the exit...

DO NOT plan the egress path to exit through another tenants space

DO NOT plan the egress path to exit through storage spaces, kitchens, mechanical rooms…or other high hazard occupancies.

But exiting through a non hazardous accessory space is acceptable, as long as there is a clear path discernable to the exit.

Where do we enter?

Prominence Number of entries Security Types

Public Employee Service Shipping/receiving

A 150x250 siteAlley

Main Street

Easy

Str

eet

Adjacentstructure

Zoning setbacks

Alley

Main Street

Easy

Str

eet

Adjacentstructure

Where do we enter?

Alley

Main Street

Easy

Str

eet

Adjacentstructure

Possible Service

Barrier!No view!

Best public/ employee entry

Possible employee entry

Now you need the insight

If the employees have to clock in, change clothes, and report to the workspace, then the lockers/lunchroom/timeclock need to be near their entrypoint

If they just walk in and go to their workstation, there’s no need for this

Now you need the insight

If there is a public/retail first floor, the street-fronts become high value, so putting employee or utility functions there would be counterproductive

If the business ships and receives high volumes of product, then the side-street and alley become high value.

Regardless, we need to keep in mind, trash storage, backup generators, and misc. delivery

Example, multi-tenant office bulding

Key issues Return on investment High net to gross ratio (what’s that?) Clear circulation/wayfinding Maximize value of perimeter glass/views Allow for street level retail

Public/employee sequence dominates…but doesn’t locate

elevators

Lobby/Reception/directory/security

Entry/vestibule

retailretail

Double loaded lobby allows two retail tenants

Single loaded would allow one larger tenant

Challenge might be identity

If its an office building…

Alley

Main Street

Easy

Str

eet

Adjacentstructure

High-value corner retail

Lower-value

streetfront retail

…but the tail can’t wag the dog

The corner retail will produce higher rental costs, but will it compromise the 15 floors of building above it?

The street-front retail will tolerate more spatial disruption due to its lower rents, but how much can we intrude on it?

Time to consider the cores

coreS?...not just one? Every floor will need

Elevator access 2 means of egress (elevators won’t count) Toilets for each gender Some electrical/telecom space Some space for ventilation/hvac

Could be a shaft Could be a fan room

A midrise building core

Will Paton, final study F2011

men

women

egress egressmechelevators

A minimal stair• 48 inches between handrails• 1.5” handrails (each side) that are 1.5” from the walls• So a single run of stairs is 54” wide• If the stair runs between 12 foot floors,• 12x12=144” of rise• divided by max riser 7.0 = 20.5 risers, say 21 at 6.8” or just

over 6 and ¾ inches.• always one less tread than riser so 20 risers at min dimension

of 11 inches so 20x11inches = 220 inches or 18 feet 4 inches of horizontal run, add 6-5 foot landings at the top and bottom if doors open into the stairs) (and, not counting the ARA), the overall inside of the straight run stair is 31’2” x 5’4” wide.

• now work out a dual run stair.

Building Planning… Part

II

Core strategies

Other core responsibilities

Besides housing egress, access, toilets and HVAC, cores often act as the primary space definition elements on a floor.

They also are often used for lateral bracing of the structural frame, with walls reinforced to be shear diaphragms or with “X” bracing or chevron bracing concealed within their enclosing walls

Core location

Core location

Lever House, NYC, Gordon Bunshaft, 1952

Core location

Sendai Mediateque, Ito atomizes the core

Considering cores…

Alley

Main Street

Easy

Str

eet

Adjacentstructure

High-value corner retail

Lower-value

streetfront retail

A minimal stair• 48 inches between handrails• 1.5” handrails (each side) that are 1.5” from the walls• So a single run of stairs is 54” wide• If the stair runs between 12 foot floors,• 12x12=144” of rise• divided by max riser 7.0 = 20.5 risers, say 21 at 6.8” or just

over 6 and ¾ inches.• always one less tread than riser so 20 risers at min dimension

of 11 inches so 20x11inches = 220 inches or 18 feet 4 inches of horizontal run, add 6-5 foot landings at the top and bottom if doors open into the stairs) (and, not counting the ARA), the overall inside of the straight run stair is 31’2” x 5’4” wide.

Stairways Two required Fully enclosed with 2

hour fire rated construction

Minimum stair width 48”

Max stair width without intermediate railing = 5’ Minimum headroom 80” from nosing line

Max height between landings = 12’-0”Minimum depth

Of Landing, 48”

Max riser 7”Min tread 11”Within 3/8 of same dimension for all steps

Max intrusion of door on landing = 7”

Stairways…cont’d

Handrail height 34” - 38”

Handrails required both sides. 1-1/4 to 2” dia, 1-1/2” from wall (clear)

Handrails must extend 12” beyond top riser, and one tread (11”min) beyond bottom tread

11”12”

Other core responsibilities

Besides housing egress, access, toilets and HVAC, cores often act as the primary space definition elements on a floor.

They also are often used for lateral bracing of the structural frame, with walls reinforced to be shear diaphragms or with “X” bracing or chevron bracing concealed within their enclosing walls

Considering cores…

Alley

Main Street

Easy

Str

eet

Adjacentstructure

High-value corner retail

Lower-value

streetfront retail

Chicken or the egg?What sets the core-to-skin distance?

How far is it from the core to the skin?

Know your typology…what’s that mean?

typology meets client culture…meets market…

Client Culture, Organization, and Form

Market needs inform

Modularity…common denominators…

• Planning grids

• Structural grids

• Lighting grids

• Power grids• Mechanical

grids

Built from the most common…and smallest acceptable unit of space

Minimum skin to core?

14’

6’

10’

10’

Minimum structural?

14’

6’

10’

10’ 10’ 10’

Check structural capabilitySteel Frame

Cast-in-Place Concrete Frame

Precast Frame

Steel R.O.T. p.356

Depth of Girders = 1/15 span (width=1/3 to 1/2 depth)Depth of Beams 1/20 span (depth of slab included in composite structures)Depth of bar joists 1/20 span (spacing 2 to 10 feet depending on decking / concrete thickness) Depth of decking and concrete for floors 1/24th of span (2 1/2 to 7 inches typical)Depth of decking for roof 1/40 th of span (1 to 4 inch decking available)

Bay proportions…are long girders better?

20’

40’

Here the girders are spanning 40’ and are framing into the columns and carry the secondary floor beams.

This requires W30x108 girdersAnd W16x26 beams

With a 5 1/4” slab over the beams that’s 6,400 pounds of steel in this bay

30”14” for ductwork, lights...

16”

Site-Cast-Concrete Systems…Basic flavors

Basically, there are 4 types of slabs an architect chooses from when considering a system for a project.

Slabs are usually flat, can be reinforced to span one way or two ways. Their span usually depends on their depth, but there is a point where the extra concrete in the depth works against the slab due to its weight.

Joist slabs usually can span farther and carry heavier loads because they eliminate concrete not contributing to the slabs strength. (hence the joists)

All diagrams from Allen “Architects Studio Companion”

One way flat slabs…will it work?

The one way slab spans between beams or columns. It requires a structural bay (spacing between columns in both directions) that is within 20% of being square.

It is usually used for light loading applications where it’s thin structural depth gives a low floor to floor height.

When heavily loaded it requires the beams below the slab, It is more desirable to NOT have these beams as they take additional labor to form and pour.

Costs 25x25 6” 40psf load about $13.80 per sq.ft. 25x25 6” 125psf load about $17.20 per sq.ft.

Span min 6’Span max 18’R.O.T. Slab depth 1/22th of span Postten rot Slab depth 1/40th of span

Min thick for 2hr = 5”Min thick for 3hr = 6 1/2”

One way joist slabs• To address heavier loading conditions, its necessary

to remove the concrete that’s acting as dead weight - working against the slab that comes along with an increase in the uniform thickness of a slab.

• This one way joist slab does just that, using prefab formwork set on a plywood deck voids are formed between the joists which make the slab lighter, and stiffer.

• The joists bear into beams (called bands) spanning from column to column. These bands give this system the ability to move columns off the grid, (as long as they still fall under the bands) allowing for more plan flexibility.

• Costs – 25x25 12” 40psf load about $14.10 per sq.ft.– 25x25 12” 125psf load about $16.50 per sq.ft.

Span min 12’Span max 45’R.O.T. Slab depth 1/18th of span Postten rot Slab depth 1/36th of span

Min thick for 2hr = 5”Min thick for 3hr = 6 1/2”

JoistSlabJoist band (beam)void

Standard Spanning elements

Solid slabs Hollow core slabs

Double tees

Rectangular beam “L” beams “T” beams

Each piece is numbered for location according to the shop drawings. This producer also dates each piece to be certain only fully cured

components are installedCastellated joint

Hollow Core slabs Like sitecast slabs, when the depth of a solid slab

increases past a certain point, the extra weight of the concrete works against the spanning member.

In precast, the hollow core slab, removes unemployed concrete increasing the structural efficiency of the slab.

Unlike the solid slab, the hollow core slab is reinforced with prestressing strands in the top and bottom of the slab.

Spanning The hollows are made in different ways by different

companies. Some have expanding air cylinders, some use pea gravel laid in the bottom half of the pour.

Span max 45’Widths 2’-0”, 3’-4”, 4’-0”, 8’-0”Span / Depth ratio 1/40Min produced depth 6” (2” increments)Max produced depth 12”Cost per s.f. topped $12.50Cost per s.f. untopped $10.50

aka the plank Like the solid slab, the hollow core slab (also known as the hollow

core plank) has castellated joints to form shear keys when filled with grout.

This helps the planks work together and increases structural efficiency. Like other precast systems when used as floors, the hollow core plank

needs a topping slab (2” or so) to level out the camber differences, make a diaphragm for lateral resistance, and make a place for electrical and hot water heating utilities.

Long beams, short planks or long

planks short beams?

One way

20’

40’

2’-8”

8”

3’-4”

• The longer a beam spans, the deeper it must be. While the plank stays pretty much the same. (the number of prestensioned strands increases)

• In this example, say the beam span is 20 feet, the rule of thumb of d=1/15 s gives 20/15=1’-4” deep. The plank spans 40 feet here and which gives an 12” plank. This makes a 2’-4” deep structural sandwich

40’

20’

40’

20’

1’-4”

12”

2’-4”

That’s a FOOT thinner! In a 8 story building it gives the owner an extra floor for FREE!

So bay size has a LOT to do with structural depth, which has a significant impact on the projects economics!

Beams & floor to floor heights…look familiar?

• Supporting the spanning member on top of the beam adds to the floor to floor height, but, if the spanning member on top of the beam is a single or double tee, the space between the top flange and bottom of the stem is available for ductwork to pass over the beam with no conflict!

Duct Space!

Duct

Mechanical PlanningIs mostly about providing ventilation…and cooling

…with big…noisy…machines

You can choose to Centralize or Decentralize the air handling machinery in the building

Centralized:Big vert shafts

Decentralized:Mech rooms each floor

Hybrid

If Shafts…plan for trunks

Don’t trap shafts behind elevators and stairs

Trunk ducts are the main ducts that emerge from the shafts

Since they serve large areas of floorspace, they contain lots of air and are bigger than distribution ducts

If Shafts…plan for trunksPlan return ducts to run inboard of supply…supply has to be delivered to the building skin, returns can be interior

Structure & trunk ducts

Plan a short structural span next to the core if possible, it makes for a thinner structural section to allow trunk ducts to pass

Short span

long span

Put it all together…Seeking modularity

You’re looking for the common denominators• Is the smallest space an increment of the largest?• Will the smallest plus a circulation path be modular with

the most frequently found space increment?• Is the structure an increment of the smallest and largest

spaces?Remember..

• Grids don’t need to be uniform• Core functions can be environmental buffers• Smaller grids spacing makes for shallower structure, very

helpful if coordinated with maximum ductwork depth• Mechanical zones are usually functional, environmental

or some combination of the two.• Ductwork is best run over circulation spaces, it gives

better acoustic isolation.