While the roofers of Pinnacle towers -Africa tallest building in Nairobi at 300 meters – will have to worry about getting the helipad-roof right , most roofers of other buildings will content with worrying more, about common but critical design elements like how well the roof will protect building occupants from the weather and fire ,how it should provide stability to the walls(for without the roof the top of the wall is weak) and finally how it will reduce heat loss and noise . In other words roofing requires great skillfulness and nerves of steel because it is neither for persons who do things by half measures nor those who are jittery about heights. This bring me to thrust of the matter-that is the the four things about roofing that will leave you looking at your house in new light.
Number one, the support structure is constructed using softwood and consist of the ridge, rafters, ceiling joists, struts, collars and ladder frames. By the way, the term soft wood can be misleading -it does not necessary refer to the strength of the wood in question. Now once this support structure is secured on the wall plate, it is then covered by one of the following roofing materials: sheet metal, clay tiles, concrete tiles, stones(such as slate), wood(such as cedar shingles),mineral felt or polyester or grass ( like reeds, straw or needle grass).
Number two, roofs are either classified as pitched or flat and further given names according to their shapes as follows:
a). Pitch roof
This is any roof having a sloping surface in excess of 10 degree pitch. Those with a single sloping surface are known as mono pitch and those with two opposite slopping surfaces are called double pitched roofs.
b). Gable roof
This a double pitched roof with one or more gable ends. A gable is the triangular part of the end wall of the building with a pitched roof.
c). Hipped roof
A hipped roof is a double pitched roof where the roof slope is turned around on the shorter sides of the building to form a sloping triangular end(that is to say, has four sloping sides).
Number three, the roof rafters are nailed to the wall plate or in area notorious for high winds framing anchors or truss clips can be used. The wall plate must be secured to the wall with straps at two meters centers. The rafters and ceiling joist near to gable end should also be tied into the wall with metal restraint straps at two meters centers.
And last, number four, heat insulation in pitched roofs is done by placing insulation materials between the ceiling joist and roof cover. Expert recommend that the roof void must remain ventilated; hence make sure the eaves are not blocked with the insulation material .
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Sources: Site carpentry and Joinery by peter Brett