Materials & Shingles · FAQ

What’s the minimum pitch for asphalt shingles?

2/12 pitch (which means 2 inches of rise per 12 inches of run) is the absolute minimum under the IRC, but only with a double layer of underlayment beneath. Below 2/12 you’re into membrane-roofing territory (TPO, EPDM, or modified bitumen).

Trill’s practical recommendation for Illinois: stay above 3/12 for asphalt and consider a metal or membrane system for anything between 2/12 and 3/12. Low-slope asphalt in our climate is reliable for 12 to 15 years versus 25 to 30 for the same shingle on a steeper slope, because water dwell time on the surface is longer and the granules wear faster. The cost difference between a low-slope asphalt and a low-slope TPO membrane is closer than most homeowners expect.