From a roof measurement to a buyable exterior takeoff

An exterior measurement — from HOVER or measured by hand — gives you areas and lengths: roof surface, ridge, hip, valley, eave and rake footage, siding facade, opening counts. That is not a materials list. Like any scope line, each measurement is an assembly that has to explode into things you can actually put in a cart.

Roofing starts with squares, not square feet

Roof area comes back in square feet; roofing is bought in squares (100 SF). So 2,766 SF is 27.66 squares — and shingles, synthetic underlayment, and starter all count off that number, each with its own waste factor. Steep or cut-up roofs waste more than a simple gable, so a good takeoff raises the factor when the pitch does.

The linear trades come off the edges

Each perimeter measurement drives a different material:

• Drip edge — eaves plus rakes, in 10-foot pieces
• Starter strip — eaves plus rakes
• Hip & ridge cap — ridges plus hips
• Ice & water shield — valleys plus eaves, where leaks start
• Ridge vent — along the ridges

One measurement set, a dozen purchase lines — each derived, not guessed.

Siding is net of its openings

Facade area alone over-orders. The real quantity is gross wall area minus the windows and doors, converted to squares with waste, plus house wrap over the full facade and J-channel around every opening. Miss the openings and you have paid for siding you will cut off and throw away.

Measured beats estimated

The point of starting from a measurement instead of an eyeball is that every quantity traces back to a number someone can check. Waste is explicit, pack sizes are real, and when the roof is 27.66 squares the order is 27.66 squares plus a stated waste percentage — not "about 30."

That is the whole idea: a takeoff you can hand to a supplier, not a rounded guess.