2 ROOFSIt is constructed to protect the building from weather (rain, wind, heat, snow, etc)Roof is the uppermost part of the building
3 REQUIREMENTS OF A ROOF Durable against various natural agencies Adequate thermal insulationWater proofFire resistantSound insulationGood drainage arrangement
4 CLASSIFICATION OF ROOFS Pitched or slopingSingle roof,Double roof,Trussed roof.Flat or terracedR.C.C roof,Madras terrace roof.CurvedShell roof,Dome roof.
5 PITCHED ROOFSThese roofs have sloping top surfaceSuitable in those areas where rainfall/snowfall is very heavySpan: clear distance between the supports of beams, roofs or trussRise: vertical distance between the top of the ridge and the wall platePitch: inclination of sides of a roof to the horizontalRidge: an apex line of a sloping roof
9 TYPES OF PITCHED ROOFS Single roofs Double or purlin roofs Trussed roofKing post trussQueen post trussMansard trussBel fast trussSteel trussComposite truss
10 SINGLE ROOF: 1.LEAN TO-ROOFS Rafters slope to one side only.Upper ends- rafters are fixed by nails to the wooden plates.Lower ends- rafters are notched & nailed to the wooden post plate.Battens are placed and fixed over rafters.Roof covering materials.Spans upto 2.5 m.
11 2.COUPLE ROOF Pair of rafters Slopes to both sides Upper ends- nailed to common ridge pieceLower ends- notched & nailed to wooden wall plates.Battens are fixedRoof covering materialsSpan upto 3.60 m.
12 3.COUPLE CLOSE ROOFTie beamPrevent from spreadingSpans upto 4.20 m.
13 COLLAR BEAM ROOF Span increase or heavy load- leads to bend Prevent by raising the tie beam1/3rd to ½ of the vertical ht. from wall plate to the ridge.Spans upto 5m
14 DOUBLE OR PURLIN ROOFS Rafters- rest at the ends on wall Purlins- intermediate supportsSpans upto 5.5 m.
15 TRUSSED ROOFA number of straight members connected in the shape of triangle and forming a frame is known as truss.Truss are provided at regular interval of about 3m along the length.Used for the span more than 5m.
16 KING-POST TRUSS King post- central post Struts- inclined members Principal rafters- support the purlinsSpans- 5 to 8 m.
17 QUEEN-POST TRUSS 2 vertical posts Straining beam 2 struts Straining sillSpans- 8 to 12 m.
18 MANSARD TRUSS Combination of king & queen post trusses. Upper portion- king post trussLower portion- queen post truss.Upper pitch- 30 to 40 degreeLower pitch- 60 to 70 degree.
19 BELFAST TRUSS/ BOW STRING TRUSS Thin sections of timberTop chord – curved30 m span – if roof covering is lightRise not more than 1/8th of the span
20 STEEL TRUSSES stronger than wooden truss Very large span (5m to 30m) KING-POST STEEL TRUSSCOMPOUND FINK & COMPOUND HOWE’S STEEL TRUSSADVANTAGE:stronger than wooden trussVery large span (5m to 30m)Easy to constructFire-proofMore rigidPermanentMore economical
21 STEEL TRUSSES…..Cont 1 Likely to get rusted DISADVANTAGE:Likely to get rustedNeed anti corrosive paints.Periodical maintenance required.USES:Building with large spanBuilding with no intermediate columns.Place of heavy rainfall of snow fall.
22 COMPOSITE TRUSS Timber and steel Tension members – steel Compression members – timberLight and economical
23 FLAT ROOFSIt is one which is either horizontal or horizontal with slope less than 10°.TYPES OF FLAT ROOFS:Madras terrace roofsReinforced cement concrete slab roof
26 REINFORCED CEMENT CONCRETE ROOF Easy to castVery smooth surfaceLength / width > 2 – one wayLength / width < 2 – two way
27 CURVED ROOFSModification of pitched roof and are frequently employed in modern age to cover large areas.Useful for assembly halls, recreation centres, factories, monumental worksPleasing appearanceTypesShell roofsDomes
28 NORTH LIGHT SHELL ROOF Mostly used in Where good day light id desired FactoriesWork shopsWhere good day light id desired
29 BARREL VAULT SHELL ROOF Long multiple cylindrical shellFeather edge beamsWhere day-lighting is not must
30 DOMES Semi-elliptical or semi-spherical Uniform or varying thickness Brick, stone, steel, wood, concrete or tile