Starter strip and ridge cap basics
These two accessories are easy to forget and easy to under-order, yet they protect the most vulnerable parts of the roof — the edges and the peaks. Here is what each does and how it is counted.
What starter strip does
Starter strip is the first course laid at the eaves and rakes, beneath the visible field shingles. Its factory-applied adhesive bonds to the bottom edge of the first row of shingles, locking them down against wind uplift, and it gives a clean, straight line along the roof edge. Skipping proper starter — or cutting up field shingles to fake it — leaves the edges prone to blow-off and can void wind warranties.
How starter strip is counted
Starter is counted by the linear feet of eave plus rake, divided by the coverage per bundle. A common factory starter such as GAF Pro-Start covers about 120 linear feet per bundle. So a roof with 80 feet of eave and 60 feet of rake has 140 linear feet of edge, needing two bundles. Manufacturers generally recommend installing starter at both the eaves and the rakes, not just the eaves, which is easy to forget.
What ridge cap does
Ridge cap shingles finish the hips and ridges — the lines where two roof planes meet at the top. These are high-stress areas exposed to wind and water from multiple directions, so they get a dedicated, often thicker, cap shingle rather than field shingles. Proper ridge cap seals these lines, gives the roof its finished look, and is where ridge ventilation is integrated into the roof system.
How ridge cap is counted
Ridge cap is counted by the linear feet of hip plus ridge, divided by the coverage per bundle. A common cap such as GAF Seal-A-Ridge covers about 25 linear feet per bundle at standard exposure. So 50 linear feet of combined hip and ridge needs two bundles. Coverage varies by product and by the exposure it is installed at, so confirm against the specific cap you are buying rather than assuming the default.
Why they get left off estimates
Field shingles dominate the order by volume, so the edge and peak accessories are the easiest line items to overlook — and running short on ridge cap halfway up a hip is a frustrating delay. Counting eave, rake, hip, and ridge lengths separately keeps them on the list. The full calculator takes those linear-foot inputs and returns exact starter and ridge bundle counts alongside the field shingles.