Tama County, IA Roof Snow Load - 20 psf
Tama County, IA roof snow load, translated
A typical heated home in Tama County is designed to carry 20 pounds per square foot of snow on its roof, per ASCE 7-22. §7.3.4's low-slope minimum of 20 psf is what actually governs on a flat or low-pitch roof here - higher than the 17.5 psf the base ground-load formula gives.
On a roof that means 44 in. of fresh snow, 16 in. once it packs down, or 4 in. of solid ice - three very different piles for the same load. 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.
Tama County in numbers
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#996 of 2,758
- Iowa rank#70 of 99
- Population16,738
- Annual snowfall, NOAA normal32.8 in.
- FIPS19171
Where Tama County ranks
#70 of 99 Iowa counties by design load, top 36% of 2,758 nationally - that's Tama County's spot. That's 1.7 psf below Iowa's own county-average design load of 21.7 psf.
FIPS 19171, population 16,738, centered near 42.0748°N 92.5294°W. ASCE 7's underlying ground snow load here is 25 psf before the code's exposure and importance factors bring it to the 20 psf design figure above.
Tama County: average annual snowfall
Tama County sees about 32.8 in. of snow most winters, per the TOLEDO 3N, IA US station's 1991-2020 NOAA normal. See the density guide.
Read this before you use Tama 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. See the methodology guide.