District of Columbia, DC Roof Snow Load - 20 psf
District of Columbia, DC: your roof's ASCE 7 snow number, in plain English
District of Columbia's roofs are built to hold 20 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. §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.
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. 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.
District of Columbia, DC: quick facts
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#525 of 2,758
- District of Columbia rank#1 of 1
- Population702,250
- Annual snowfall, NOAA normal15.8 in.
- FIPS11001
District of Columbia by the numbers
Nationally that's #525 out of 2,758 rated counties, the top 19%; within District of Columbia alone, District of Columbia ranks #1 of 1. District of Columbia's figure lands almost exactly on District of Columbia's own county-average of 20 psf.
District of Columbia, FIPS 11001, is home to 702,250 people near 38.9042°N 77.0165°W. Its 25 psf ground snow load figure is the map value; 20 psf is what a roof is actually designed for.
District of Columbia's snowfall, most winters
15.8 in. a year: that's District of Columbia's NOAA 1991-2020 snowfall normal, measured at BELTSVILLE, MD US (9.8 mi away). See the density guide.
Before you rely on District of Columbia's number
Treat the District of Columbia 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. See the methodology guide.