Roofing guides
Plain explanations of how roofs are measured and quoted. Each guide does one job, carries a worked example through, and links to the sources it relies on.
How to measure a roof
From the footprint to roofing squares in five steps: measure from the ground, find the pitch from the attic, convert to roof area, then add waste for shingles. One example runs through every step so you can check it with the calculator.
How to read a roofing quote
What the scope should say, how to check the units, the lines you'll usually see, and what to get in writing before you sign.
What a roof is made of
A quick reference for terms you'll meet in quotes. The numbers in the drawing match the list.
- ShinglesThe weather surface. Asphalt shingles overlap in courses from the eave up.
- UnderlaymentA water-resistant sheet under the shingles. Many codes require two layers on slopes from 2/12 up to 4/12.
- Decking (sheathing)Plywood or OSB panels fastened to the rafters. Damaged sheets are often found only during tear-off.
- RaftersThe sloped framing members that carry the roof.
Roof shapes at a glance
Shape affects how many sections you measure and how much shingle waste a roof produces.
GableTwo slopes meeting at a ridge, with a triangular wall at each end. 
HipSlopes on all four sides, meeting at hips and a short ridge. 
ShedOne plane sloping in a single direction. 
GambrelTwo slopes on each side, the lower one steeper. 
MansardSteep lower slopes on all four sides under a low-pitched top. 
Flat (low-slope)Nearly level; uses membrane systems rather than shingles.
Each pitch on a roof has its own roof-area multiplier. The roof pitch calculator gives it for any pitch, and the quote checker compares a quote's quantities with the roof size you work out.