Corrugated Sheet Roofing, Corrugations Corrugated sheet roofing material is widely available and easy to use. Corrugations should run in a straight line between the highest and lowest points, and at a right angle to the purlins (the intermediate supports). The overlaps (ends and sides) depends upon the sloop of the roof. Purlin spacing should suit the end laps required for the size of sheet to be used. Sheets should be laid so that the side overlaps are directed away from the prevailing wind. All purlins should be in one plane and parallel to each other. They should be properly anchored to the supporting superstructure. Ends of all sheets should be supported by purlins. The free overhang at the eaves should not exceed 300 mm. 8 mm diameter (min) hook bolts, crank bolts or coach screws, should be inserted through 10 mm diameter drilled holes.- NEVER PUNCHED - in the crown of the corrugations. Nuts or screws should be tightened lightly at first, and then tightened again when a dozen or more sheets have been laid. At intermediate purlins, they should not be tightened in an attempt to make the sheet rest on the purlins. A cat-ladder or roof board should always be used when working on a roof for safety of the person and to avoid damage to the roofing material. Installation of corrugated roof sheeting These notes are intended to cover the use and installation of corrugated roof sheets such as PVC, other plastics and bitumen fibre sheets. Although very different as materials and where they are used, they do have similar properties regarding flexibility and weight. One advantage of these corrugated materials is that it is far more rigid than a flat sheet of a similar type and thickness. This enables considerable savings in both weight and cost, it also makes the sheet relatively easy to handle. Generally all these types of material can be used either as roofing or vertical cladding. Most of these sheeting tends to be susceptible to condensation when used as cladding for outhouses etc. - being relatively thin they tend to have low thermal insulation properties. Condensation will be reduced if the interior of the structure is well ventilated.
