Washtenaw County, MI Roof Snow Load - 20 psf
How much snow is too much for a roof in Washtenaw County, MI?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Washtenaw County to carry. The physics-based figure alone would be 14 psf, but ASCE 7's own low-slope minimum (§7.3.4) sets a floor of 20 psf for flat and low-pitch roofs here, which is the number that actually governs.
Picture it, not just weigh it: 44 in. if it's fresh powder, 16 in. once it settles, or a mere 4 in. if it's ice. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
Washtenaw County, MI: quick facts
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#555 of 2,758
- Michigan rank#59 of 70
- Population373,875
- Annual snowfall, NOAA normal32.9 in.
- FIPS26161
How Washtenaw County compares
20 psf ranks #555 of 2,758 US counties with a mapped snow load (top 20%) - and #59 of 70 in Michigan. That's 11.7 psf below Michigan's own county-average design load of 31.7 psf.
Population 373,875 (FIPS 26161), roughly 42.2522°N 83.8434°W. The 20 psf ground snow load ASCE 7-22 maps here becomes 20 psf once the code's own design factors are applied.
Typical snowfall in Washtenaw County, MI
NOAA's 30-year normal for Washtenaw County: 32.9 in. of snow a year, from the CHELSEA, MI US station. (fresh vs. packed vs. ice explains why.)
What this Washtenaw County figure assumes
This is a county-level reference figure for a typical heated home built to Risk Category II (ordinary residential), on a partially exposed lot - the assumptions ASCE 7-22 itself treats as the default case. A steeper roof, a fully exposed hilltop lot, an unheated structure, or a higher risk category all change the actual number.
Washtenaw County's permit office wants an address-specific figure, not this county average - the ASCE 7 Hazard Tool is free, takes under a minute, and outputs a PDF most reviewers accept. See the methodology guide.