Cant Strip
A triangular piece of material placed at the junction of a flat roof and a vertical surface to create a gradual transition. Cant strips prevent membrane cracking at 90-degree angles.
What Is a Cant Strip
A cant strip is a triangular piece of material installed where a flat roof surface meets a vertical wall or parapet. It provides a 45-degree beveled transition so the roofing membrane is not forced into a sharp 90-degree bend that would stress and crack the material over time.
Materials and Installation
Cant strips are made from wood, perlite board, polyisocyanurate insulation, or fiber-cement. The standard size creates a 45-degree angle with legs typically measuring 3 to 4 inches. The strip is set in adhesive or mechanically fastened before the membrane is applied over it.
Insurance Relevance
When a flat roof is replaced after storm damage, cant strips are part of the scope. If existing cant strips are deteriorated, they need replacement before the new membrane is installed. This is a legitimate line item that adjusters sometimes overlook.
Frequently asked questions
A cant strip is a beveled piece of material (typically wood, perlite, or polyiso) placed where a flat roof meets a vertical wall. It creates a 45-degree transition that prevents the roof membrane from cracking at the sharp 90-degree angle.
Most roofing membrane manufacturers require cant strips at roof-to-wall transitions. Without them, the membrane is forced into a sharp bend that creates stress points and leads to premature failure.
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