Garfield County, MT Roof Snow Load - 20 psf
Garfield County, MT roof snow load, translated
A typical heated home in Garfield County is designed to carry 20 pounds per square foot of snow on its roof, per ASCE 7-22. The physics-based figure alone would be 17.5 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.
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. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
Garfield County, MT: quick facts
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#1,288 of 2,758
- Montana rank#20 of 29
- Population1,181
- Annual snowfall, NOAA normal32.2 in.
- FIPS30033
Where Garfield County ranks
#20 of 29 Montana counties by design load, top 47% of 2,758 nationally - that's Garfield County's spot. Montana counties average 19 psf; Garfield County runs 1 psf higher than that.
FIPS 30033, population 1,181, centered near 47.2672°N 106.996°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.
Garfield County: average annual snowfall
Garfield County sees about 32.2 in. of snow most winters, per the MALTA 35 S, MT US station's 1991-2020 NOAA normal. 59.8 mi is a real gap between Garfield County and its nearest reporting station, so local snowfall can diverge from this figure, especially near elevation changes. See the density guide.
Read this before you use Garfield 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. (How this figure is calculated.)