Shingles and materials
Work out how many bundles or panels to buy, how much attic ventilation you need, and the model code rules on slope and re-roofing.
Guides and calculators
Shingle Calculator: How Many Bundles Do You Need?
Enter your roof area and waste allowance to get squares and shingle bundles, with the formula and manufacturer guidance on bundles per square.
Shingles and materialsMinimum Roof Pitch for Asphalt Shingles
The 2021 IRC allows asphalt shingles on slopes of 2/12 or more, and requires double underlayment from 2/12 up to 4/12. Here's what that means for your roof.
Shingles and materialsCan You Put New Shingles Over Old Shingles?
When the International Residential Code allows a roof recover, when it doesn't, and what to ask your contractor before skipping a tear-off.
Shingles and materialsMetal Roof Calculator: Panels and Roof Area
Work out how many metal roof panels you need from the eave length, slope length and panel coverage, plus the code's minimum slopes for metal roofs.
Shingles and materialsAttic Ventilation Calculator: The 1/150 and 1/300 Rules
Work out your attic's required net free vent area using the 2021 IRC's 1/150 rule and its 1/300 exception, with the conditions and a worked example.