A roof takeoff is the order, not the measurement

A measurement tells you the size of the roof. The takeoff is what you buy: bundles, rolls, sticks of metal. Short, and the crew waits on a delivery. Long, and you are storing shingles you cannot send back.

1. Buy packages, not squares

A square is 100 square feet. Most architectural shingles pack 3 bundles to a square. Twenty-four squares is 72 bundles, and that is before you cut anything.

Underlayment is whatever the roll says. A common synthetic covers about 10 squares. Felt covers less. People order felt as if it were synthetic and run out on the back slope.

Drip edge is a 10-foot stick. Eaves plus rakes, divided by 10, then round up. Corners waste a foot or two, so add a couple of sticks.

Ridge cap and starter are separate from the field shingles. So are pipe boots and vents. Coil nails on a normal nail-down run about 2 to 2.5 pounds a square. If you are replacing decking, a sheet of OSB is 4 by 8, 32 square feet. Count sheets.

2. Do not order from the ground

If your report already gives roof area, use that. The bad number is the one somebody paced off in the yard. A 6/12 is about 12 percent more roof than the footprint. A 9/12 is 25 percent more. Forget the pitch and every slope comes up short.

3. Waste is the part you still pay for

Hips, valleys, and anything sticking through the roof turn into offcuts. On a simple gable, 10 percent on the shingles is usually enough. On a cut-up hip roof, start at 15. Steep roofs waste more, because the pieces get smaller. Underlayment can stay near 10 percent unless the roof is chopped up. The extra bundles cost less than sending a driver back at 2 p.m.

4. Do the list before the truck is loaded

The order goes wrong in the driveway: no pitch, no drip edge, or a 32 that got typed as 23. Write the takeoff while the measurement is still open, and round to whole bundles and whole rolls.

If the job is in Skallix, keep the measurement on the job with the estimate. The order should not be a photo of a notebook.