Iron County, MO Roof Snow Load - 20 psf
How much snow is too much for a roof in Iron County, MO?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Iron County to carry. ASCE 7's low-slope-roof minimum (§7.3.4) raises the governing figure to 20 psf - higher than the 14 psf the ground-load formula alone would give, and the code says use the larger one.
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. This is a meaningful design load - most modern-code homes handle it fine, though an addition, a carport or a flat-roofed section can be a weak spot.
Iron County, MO: quick facts
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#1,116 of 2,758
- Missouri rank#64 of 115
- Population9,420
- Annual snowfall, NOAA normal8.7 in.
- FIPS29093
How Iron County compares
20 psf ranks #1,116 of 2,758 US counties with a mapped snow load (top 40%) - and #64 of 115 in Missouri. 18.6 psf is Missouri's typical county figure - Iron County beats it by 1.4 psf.
Population 9,420 (FIPS 29093), roughly 37.626°N 90.6996°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 Iron County, MO
NOAA's 30-year normal for Iron County: 8.7 in. of snow a year, from the FARMINGTON, MO US station. (fresh vs. packed vs. ice explains why.)
What this Iron 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.
Iron 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. Details: the calculation guide.