THE ROOF

ROOF CLADDING

In addition to the roof structure being fixed to the supporting wall, the cladding must be able to resist and transfer the wind loads to the purlins. Purlins are therefore important structural members of the roof and flat boards should not be used for this purpose. Purlins should be either 2” x 3” or 1” x 4” at no more than 2’0” spacing. Purlins should be fixed to each rafter passed over using hurricane straps or metal cleats.

• Corrugated galvanized steel sheeting is the most commonly used form of cladding in the Eastern Caribbean. Sheeting which is too thin and with inadequate numbers of fixings is extremely vulnerable during hurricanes. The minimum thickness of corrugated steel sheeting should be 6mm.

• Sheets should be fixed to the purlins using self-tapping screws or galvanized nails with large washer.

• At the eaves and ridge as well as the gable ends, the fitting should be two corrugations apart, and for the rest of the roof, no more than three corrugations apart.

• The corrugated sheeting should be properly overlapped (at least 2 1/2 corrugation) to prevent water from blowing under the seam.

• Roof capping should be made from materials as strong as the sheeting itself, it should be bolted or screwed down to the purlin on either side of ridge or ridgeboard or hip.

• Spaces between the sheeting and the wall plate should be closed up to prevent the wind from getting under the sheeting and lifting it. This can be done by nailing a fascia board to the wall plate and rafters.

CONNECTION OF SHEETING & CAPPING: Every corrugation sheeting near the eaves and Ridgeboard should be bolted and nailed to purlings. For rows in between at least every other corrugation. Self tapping screws or galvanized nails with large washers and protex to prevent leaking.