· Structure: This refers to the part of the roof that bear the weight, both of the roof itself as well as weather effects like rain and snow. It is mostly made out of timber or steel. Whichever the material used, the structural frame of the roof consists of these main members;
o Truss: This is the most identifiable member of the roof structure, with its triangular form consisting of rafters, ties, struts and a kingpost. It is used to span the shorter side of the building and transfers its weight and loads to the ring beam.
o Rafter: This is a linear member and is meant to transfer its weight to two walls or beams directly. It is common with flat roofs and lean to roofs. In most of these cases, one wall is usually higher than the other, thus providing a gradient for fall.
o Ridgeboard: Used to link rafters. Cannot be attributed any structural assignment though.
o Purlins: Also used in the same way as the ridgeboard, only that the ridgeboard is at the apex of the roof while purlins are on either side.
o Valley / Hip board: These are used where the roof turns, either forming a valley or hip. These act as rafters and as such constitute structural members.
· Cover: Roof cover is provided in different forms and materials, with examples here including;
o Clay Tiles: Probably the most common roof covering material around. They are preferred for their heat insulation properties as well as noise absorption and superior finish. They have a disadvantage of weight, requiring a stronger frame.
o GCI Sheets: The initials stand for Galvanised Corrugated Iron Sheets. These are also very common and the pros and cons can be said to be in contrast with the former.
o Concrete: This is mostly in flat roofs, although not very common these days. This is due to the problem of rainwater disposal as well as weight. Where used, this is enhanced by the application of waterproofing solutions like Tar Felts.
· Rainwater disposal: This is a very important part of the roof as it takes care of rainwater in an organized manner, by directing it to appropriate areas for disposal or even collecting it for domestic use. This includes of gutters and downpipes. The conventional rainwater goods were made of steel plates although the use of PVC is slowly gaining momentum. Concrete gutters are also done in some cases.