Presentation on theme: "Roofs are one of a building’s primary elements and play a major part in giving a building its character. There are several different types of roof in."— Presentation transcript:
1 Roofs are one of a building’s primary elements and play a major part in giving a building its character.There are several different types of roof in this one building.RoofsSubtitle
2 A roof must have the following qualities: A roof must be weather resistant to rain, snow, wind and sun.The durability of a roof should be equal to or in excess of those materials used in the remainder of the building.A roof should have good thermal insulation properties.A roof should require a minimum of maintenance.A roof should be constructed in such a way as to retain structural stability when dead and imposed loads are applied to it ( dead loads is the weight of materials used to make the roof, imposed loads are loads created by wind, snow, etc.
3 Roof ElementsWhen designing a roof the following points should be considered in relation to its final appearance.PitchThe steeper the pitch the greater the roof area visible. This will result in a larger roof space, you can also use smaller cladding units such as plain tiles and slates. Pitched roofs are the most suitable in countries where there is a high rain fall.CoveringsMaterials used for roof coverings should harmonise with the local surroundings. These materialsshould be fit for purpose in theirability to keep out the elements,thermal insulation, durability andappearance.Concrete interlocking roof tiles
4 Roofs Valley Rafter Ridge Hipped End Verge Jack Rafters Common Rafters EavesGable EndLean-toRoofFlat Roof
5 Terminology Wall plate Usually 100 x 50 mm softwood timbers are fixed to the top ofload bearing walls to distribute loads and provide fixings forroof timbers.Ceiling joistThese are timbers which provide a support for fixing ceilingfinishes and act as a collar to prevent rafters spreading.Common raftersThese are inclined timbers fixed between wall plate and ridgewhich transmit live and dead loads to wall plate.RidgeThe ridge is a horizontal board set on edge to which therafters are attached (not required on trussed rafters).
6 Terminology Hip Rafter A hip rafter is a rafter running from the wall plate to the ridgewhich forms the external angle of the sloping side of a roof.PurlinThis is a horizontal roof member supporting the rafters andusually at right angles to these. This enables small sectiontimbers to be used for the rafters.HangersThese are timbers hanging from the purlins to the ceiling joistto give additional support to binders.FasciaA board fixed vertically to rafter ends, which provide an additional fixingfor gutters.
7 TerminologySoffitA horizontal board fixed to the underside of the rafter outsidethe building.BargeboardVerge or gable board.EavesThe lower part of the roof, which usually includes the end ofthe rafter, ceiling joist, soffit, fascia and gutter.DormerA vertical window coming through a sloping roof.ValleyThis is the name for the intersection between two sloping surfaces,forming an internal angle ( the opposite to a hip).
8 Pitched roofIf the roof space is or may be intended to be used in the future, the structure should be designed accordingly.Roof with a gable end
10 Pitched roof with dormer windows A pitched roof with dormerwindows.Timber to support the dormer windowLay boardWhen a steep pitched roof is used in domestic construction dormer windows can be used to create additional head room in the roof space. This allows the roof space to be utilised for habitable rooms.Common Rafter
11 Roof parts Ridge Dormer window Barge board Gutter chimney Down pipe DoorEaves detail
15 Traditional cut roof structure A traditional cut roof was the first development to create pitched roofs as we know them today.This type of roof structure is still widely used for individual dwellings or for roofs of a complicated shape.The timbers rafters are cut individually and nailed into position.A purlin is often placed half way up the length of the rafter to help support the roof and allow smaller sections of timber to be used.Common raftersSteel purlinPad-stone built into the wall to help distribute the load of the roof over a larger section of wall.
16 Trussed raftersA high percentage of roofs designed now are constructed using prefabricated trussed rafters. They have been developed since the mid 1960’s.The principal disadvantage is that the roof space is occupied by a large number of timber sections.The following are the main reasons for developing truss rafters:1.Smaller and light sections of timber can be used.2. Speed of erection.3. Semi-skilled labour can be used.4. Eliminates the need for purlins and ridge boards.5. Loadbearing partitions are eliminated, allowing greater freedom of internal room arrangements.