Ontonagon County, MI Roof Snow Load - 49 psf
Ontonagon County, MI roof snow load, translated
A typical heated home in Ontonagon County is designed to carry 49 pounds per square foot of snow on its roof, per ASCE 7-22.
On a roof that means 107.8 in. of fresh snow, 39.2 in. once it packs down, or 9.8 in. of solid ice - three very different piles for the same load. This is a serious structural load - older homes built before modern snow-load provisions, or ones with low-slope or flat roof sections, are worth having checked.
Snow on Ontonagon County's roofs right now?
Ontonagon County, MI: quick facts
- Design roof snow load49 psf
- Ground snow load, ASCE 7 map70 psf
- National rank#25 of 2,758
- Michigan rank#10 of 70
- Population5,824
- Annual snowfall, NOAA normal177.7 in.
- FIPS26131
Where Ontonagon County ranks
#10 of 70 Michigan counties by design load, top 1% of 2,758 nationally - that's Ontonagon County's spot. Michigan counties average 31.7 psf; Ontonagon County runs 17.3 psf higher than that.
FIPS 26131, population 5,824, centered near 46.8352°N 89.2769°W. ASCE 7's underlying ground snow load here is 70 psf before the code's exposure and importance factors bring it to the 49 psf design figure above.
Ontonagon County: average annual snowfall
Ontonagon County sees about 177.7 in. of snow most winters, per the ONTONAGON 6 SE, MI US station's 1991-2020 NOAA normal. See the density guide.
Read this before you use Ontonagon County's figure
The figure above assumes the case ASCE 7-22 treats as typical: a heated, ordinary-occupancy home on a partially exposed site. Change any of those - exposure, heating, roof pitch, occupancy category - and the real design number moves.
A building permit needs the number at your exact address, not the county average - the free ASCE 7 Hazard Tool returns that from your coordinates in about a minute and produces a PDF a plan reviewer will accept. Details: the calculation guide.