Skip to Main Navigation Skip to Content

Under One Roof

Canadian Roofing Reference Manual

2.4.2 Screw Type Fasteners

Because of their great holding power, screws are more widely used than nails or staples in roofing. This is particularly true in the case of steel deck assemblies where the insulation, and sometimes the membrane cover must be mechanically attached to the deck to meet the specification requirements for wind uplift resistance.

Even if the roof system itself is not mechanically fastened, most single ply assemblies require the mechanical attachment of battens, perimeter restraint strips, edging and termination or compression bars as part of the assembly. These are almost always attached using screw type fasteners instead of nails or staples.

One advantage of screws is that they may be removed without causing damage to the workpiece. Although screws are costlier, their neat appearance and ease of application for certain jobs make them the better choice.

It is important when purchasing screws to specify the length, gauge, number, type of head, type of material and finish. Most insulation and membrane screws used in roofing are treated to be corrosion resistant. They also have especially designed threads and heads to prevent the fastener from backing or popping out once installed. When fastening insulation, or the membrane, a plate must always accompany the screw. These plates or disks provide the clamping force necessary to prevent the material from blowing off under pressure and the screw from pulling through the membrane or insulation. Plates are usually made of metal or hard plastic.