SnowLoadCheck

Dallas County, IA Roof Snow Load - 20 psf

Dallas County, IA: your roof's ASCE 7 snow number, in plain English

Moderate
20 psf

Dallas County's roofs are built to hold 20 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. ASCE 7's low-slope-roof minimum (§7.3.4) raises the governing figure to 20 psf - higher than the 17.5 psf the ground-load formula alone would give, and the code says use the larger one.

In depth, not weight: that's roughly 44 inches of fresh, light snow, 16 inches of old, settled snow, or as little as 4 inches of solid ice - snow that heavy is rare here but ice from a freeze-thaw cycle adds up far faster than the depth suggests. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.

Dallas County, IA: quick facts

Dallas County by the numbers

Nationally that's #635 out of 2,758 rated counties, the top 23%; within Iowa alone, Dallas County ranks #47 of 99. 21.7 psf is Iowa's typical county figure - Dallas County comes in 1.7 psf under it.

Dallas County, FIPS 19049, is home to 115,343 people near 41.6853°N 94.0407°W. Its 25 psf ground snow load figure is the map value; 20 psf is what a roof is actually designed for.

Dallas County's snowfall, most winters

32.8 in. a year: that's Dallas County's NOAA 1991-2020 snowfall normal, measured at JAMAICA 3.2 S, IA US (15.9 mi away). See the density guide.

Before you rely on Dallas County's number

Treat the Dallas County figure as a starting point, not a final answer: it assumes standard occupancy, a heated structure and a moderately sheltered site, per ASCE 7-22's own defaults. Exposed terrain, an unheated building or a steeper roof all shift the real number.

For a real application, skip the county number and go straight to the ASCE 7 Hazard Tool - enter your coordinates and it returns a site-specific figure a plan reviewer will recognize. (How this figure is calculated.)