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ROOF

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From the earliest times, humans and their ancestorssought protection from the elements of nature, changing

seasons and predators, in natural shelters such as cavesand rock overhangs.

Gradually, they learned to improve their caves with

inlaid stone floors, walls at the entrances and fireplaces.Ultimately they began creating entirely new habitats

in locations that had no natural shelter.

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Shelters built from natural materials indicates that theyhad knowledge of the stress, strain and insulation

properties (heat, cold and water-proofing) of thematerials used.

The use of hand-made bricks or stone blocks indicated

knowledge of properties such as compression forces.

The symmetrical shapes of the designs indicated theknowledge and application of the principles of

geometry.

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Natural features, caves and overhangsNatural shelters like caves or overhangs were usedas homes. Little or no building materials were used.

http://mccoy.lib.siu.edu/illinois/images/cave-n-rock.gif

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Crude shelter

Temporary structures that needed little workmanship.Materials found nearby were used and arranged on acrude framework of branches.

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Beehive hutA typical building style of the Nguni people (Zulu andXhosa). Vertical branches were stabilised withhorizontal bracing with no distinction between the

walls and the roof. The sapling structure was boundtogether by grass fibre ropes and the grass coveringwas 'sewn' to the structure with grass rope.

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Cone on cylinder

A typical style among the Tswana, Sotho and Vendapeople. The roof is separate and can be clearlyidentified. The roof was made from grass and thewalls from daga or a type of cement

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Hipped-on cube

Western influence led to the introduction of the 90wall construction. The wall layout also dictates theshape of the roof. Walls are higher and doorwayslarger.

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FUNCTION

To keep out rain, wind, snow & dustTo prevent excessive heat loss in winter

To keep the interior building cool in summer

Designed to accommodate all stressesencountered

Designed to accept movement due to changesin temperature & moisture content

To provide lateral restraint & stability to adjacentwalls

To resist penetration of fire & spread of flamefrom external sources

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TYPES OF ROOF

Flat RoofIts not perfectly flatMust have a slight slope for drainage

Shed Roof

A single slopeGable Roof2 slope meeting at ridge. 2 walls extends tothe ridge

Hip Roof2 gable, pyramid should be considered as ahip roof

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Gambrel Roof

4 slopes in one direction, the typical

barn roof Mansard Roof

2 gambrels

Basically is to the gambrel what the hip is to gable

Pitched Roof

drains water

insulates main area of heat loss

support snow load

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Shed roof

http://www.behmdesign.com/garageplans/t360-1.jpghttp://marshall.csu.edu.au/html/ONeill/JDB_House/JDB_Shed_Roof.jpg

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Hip Roof

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FLAT ROOF & PITCHED ROOF

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Mansard Roof

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Gambrel Roof

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FLAT ROOF

Its not perfectly flat, slightly slope which is less than10.

This roof is been used in hot climates

where water accumulation is not a

problem. (less rain)

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ADVANTAGES OF FLAT ROOF

a) Less material is being used than in a sloped roof

b) The rooftop is potentially useful as a terrace or sleepingporch

c) Potentially pleasing appearance

d) Easier to build than a sloped roof

WATERPROOFING THE FLAT ROOF

a) The flat roof relied on some kind of membrane forkeeping moisture out.

b) The slight slope of flat roof directs standing moisture todrains at edges.

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DISADVANTAGES OF FLAT ROOF

a) Roof elements cant overlap, hence waterproofing must

be more complex and more thorough.

b) Drainage isnt automatic. Unless properly designed &

constructed, pools of water will collect on the surface

causing local variations in temperature. This will resultin deterioration of the covering finally leading to highmaintenance cost.

c) It have little or no space below roof to accommodateservices.

d) It have limited capacity for insulation

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PITCHED ROOF

Roof whose angle of slope to the horizontal liesbetween 10 - 70.

Construction cost for pitched roof is higher than flatroof and more material is needed.

Theres bigger space below the roof than flat roof

can be made as attic.

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PITCHED ROOF DESIGN

The slope for pitched roof depends on the rain (howheavy the rain is, frequency of the rain) in a year.

In Malaysia, the roof built at West Coast Malaysia &

East Coast Malaysia is different due to the factor ofwind and rain.

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TERMINOLOGY IN PITCHED ROOFSTRUCTURE

Roof - The entire covering assembly

Pitch Rise over run

Substrate The decking that carries the roof material

Eaves Roof overhang

Ridge The peak of 2 or more slopes

Valley An inverse ridge

Ceiling The finish material that is attached to theunderside of the roof

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1

3

2

4

5

Some Of The Roof Elements

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This are the names of some of the pitched roof

elements which been labeled on previous slide:

1. Asphalt Shingles

2. Rafter

3. Ridge4. Valley Rafter

5. Collar Beam

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Some parts of the roof

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This are the names of some part of the roof elements

which been labeled on previous slide:

1. Ridge

2. Gable

3. Dormer

4. Roof Deck

5. Rake

6. Eave

7. Valley

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Ridge

- spine of the roof

- A pitching plate for the rafters that are nailed to eachother through the ridge board

Collars

- Its an extra ties to give additional strength & are placed atpurlins level

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Eaves

- Eaves of a roof is the lowest edge that overhangs the

wall, thus giving the wall a degree of protection- Also provides the fixing medium for the rainwater

gutter.

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PITCHED ROOF STRUCTURE

Depends on different types roof structure system, roofstructure can also include the followings:

a) Purlins

b) Rafter

c) Trusses

d) Beams

e) Girders

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Beam

- member that span across the openings & support

structure or loading above them.- Beam usually in timber, steel & reinforced concrete.

Purlins

- Act as a beam reducing the span of the rafterenabling an economic section to be used

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Girder

- A main horizontal or near horizontal structuralmember that supports vertical

loads.

- It may consists several pieces.

Rafter

- One of the series of structure of a roof

designed to support roof loads.

- Roof structural failure usually begin with

rafter deflection or rafter spread.

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Beams In Roof Structure

http://www.taima.org/img/miasa/miasa116.jpghttp://people.whitman.edu/~templeton/New%20Science%20Building%20Photos/2002-01/atrium%20roof%20monitors%20(in%20order)/01%20roof%20mon%20glu-lam%20beams.JPGhttp://www.gbt.org/timberframe/shop2/P8300099.JPG

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Purlins In Roof Structure

http://www.roundmaine.com/images/purlins3.jpghttp://www.hadleygroup.co.uk/purlins.jpghttp://www.gbt.org/timberframe/shop2/P8300099.JPG

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Girder

GIRDER

http://project.3wstudios.com/core_images/girder.gif

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RAFTER

http://images.google.com.my/imgres?imgurl=www.sindrey.com/Webpics/Rafter.jpg&imgrefurl=http://www.insanemembrane.com/domblog.nsf/wDocuments%3FReadForm%26Start%3D1%26Count%3D1000%26ExpandView%26View%3DwDocuments%26Cat%3DMisc&hl=en&h=600&w=762&prev=/images%3Fq%3Drafter%2B%26start%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26sa%3DN

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TRUSS

Roof structures can be formed very simply using trussedrafters.

These are made from small section timber and comprisethe rafters on the roof slopes, a horizontal to support the

ceiling, and various combinations of cross members toform a frame or truss.

RAFTER

COLLAR

TIE

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The members are usually fixed together using metalplate connectors.

The trusses are designed and produced by themanufacturer to suit the span and profile of a roof.

They are a very cost effective way of forming roofs ofhouses and are often seen on building sites.

T Of T

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Warren Truss

Pratt Truss

Fink Truss

Howe Truss

Types Of Truss

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King Post Truss

TIE

PRINCIPAL

RAFTER

KING POST

STRUT

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Elements Of Roof

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TYPES OF SHINGLES

Wood fire hazard unless treated

- expensive material & labour

Asphalt

Fiberglass

Slate split & punched, fire resistant

- heavy on structure, expensive

Tile

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PTICHED ROOF FAILURE

Symptom usually include widespread

sagging where roof covering has dished

and ridge lines are bowed over strutting

points.

Look at the ridge

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A ridge sag on 60 years old brick home

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WHY PITCHED ROOF FAIL?

Improper design or poor design

- under design of roofing members

sizing, spacing and support

Inadequate or incorrect support of roof trusses

Overloading to roof framing

- for example replacing corrugated ironby terracotta tiles.

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Deterioration

- Timber pest damage where weakened

structure timbers are unable to supportnormal roof loading

- Corrosion of roof fixing where water has

penetrated the roof covering or where the

nails and plate connection are subjected to

an aggressive salt environment near the

coast.

Inadequate repairWeather related influences (strong wind, snow

storms etc)

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Lack of precaution taken during construction process cause thepartially constructed pitched roof collapse due to strong wind.