Roofs and wall Flashcards
Tell me about a Traditional pitched roof and the structure.
Ordinary pitched roof is based on a triangle. Most rigid and economical form for a loading bearing structure.
roof covering weight is carried by the rafter.
Rafter - head meets at the central ridge at the top of the roof
Lower end - fixed to the timber wall plates, bedded on the exterior wall (helps to distribute weight evenly.
Ceiling joist supports usually support the ceiling plasterboard
what is a double roof aka Purlin roof?
Purlin is a structural timber that supports the rafter between the wall plate and the ridge.
it reduces the spans of the rafter and allows lightweight timbers to be used.
Purlin size is kept to a minimum by diagonal struts. struts transfer some weight back to the center of the ceiling joist.- Binder and hangers may be used to give support to relatively lightweight ceiling joists.
What is trussed roofs and the structure?
Trussed roof is made out of trussed rafters.roof is lightweight and fixed to the walls with steel anchor straps to resist wind pressure.
They are factory made and delivered to site for assembly.
they transmit their weight to the exterior wall.
Each truss combines two rafters, a joist and strut bracing in a single fame.
The trusses are spaced a maximum distance of 600mm apart, linked with horizontal and diagonal bracing member
What roof covering layer was used and is used now and Name the three roof coverings?
1945 - roof covering had a layer of felt or breathable underlay that was under the tile lath and above the rafter.Made the roof water tight.
1950-2000-Bitumen impregnated felt was used, usually black in colour and has a coarse texture to its finish.
2000 onwards - Vapour permeable felt or membranes have been used. Keeps the water out but allows vapour to go through - reduces the chance of condensation in the roof space.
Roof covering
Slate -
Clay titles -
Concrete tiles -
What are flat roofs and the two main types of flat roofs?
Flat roofs are roofs that are laid at an angle of up to 10 degrees from the horizontal.
two main types of flat roofs are:
1. Timber - in warm flat roof the thermal insulation is above the deck of the roof but below the water covering.Doesnt need to be ventitlated - roof temperature is the same as the room below.
cold flat roof - insulation located just above the ceiling - space has to be ventilated to stop condensation developing.
2.Concrete - main issues with old concrete flat roofs is rain penetration, condensation and mould.flat roof has been replaced by pitched roof under social housing moderation scheme.
Both flat roofs were built in the past without any insulation
Different covering of flat roofs - built up felt, asphalt,glass fibre, purpose made ruberiod, metals
describe an internal wall finish and external wall finish
Internal wall finish - could be made of brickwork or blockwork depending on how old the property is and if they have to support the floor above.
carried out using plasterboard. Can be finished using a thin plaster skim coat or the joints between the plasterboards taped and finished ready for decorating.
Internal stud partition walls are finished using plasterboards
External wall finish - finish for external wall is sand and cement render.the render mix is typically brick block or stone depending on the background.
Render is applied in two coats - strong sand and cement mix and the final coat is weaker mix.Once final coat starts to set it is rubbed up to leave a smooth finish. Usually painted using masonry paint.
other render finish - pebble dashing, tyrolean, ashlar jointing and special materials.
