Fairfax County, VA Roof Snow Load - 20 psf
How much snow is too much for a roof in Fairfax County, VA?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Fairfax County to carry. 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.
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. Modern-code homes carry a load like this without issue; an older addition, a carport, or any flat-roofed section is where it is worth checking first.
Fairfax County, VA: quick facts
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#508 of 2,758
- Virginia rank#12 of 110
- Population1,160,925
- Annual snowfall, NOAA normal18.5 in.
- FIPS51059
How Fairfax County compares
20 psf ranks #508 of 2,758 US counties with a mapped snow load (top 18%) - and #12 of 110 in Virginia. That's 1.7 psf above Virginia's own county-average design load of 18.3 psf.
Population 1,160,925 (FIPS 51059), roughly 38.8295°N 77.2733°W. The 25 psf ground snow load ASCE 7-22 maps here becomes 20 psf once the code's own design factors are applied.
Typical snowfall in Fairfax County, VA
NOAA's 30-year normal for Fairfax County: 18.5 in. of snow a year, from the VIENNA, VA US station. (fresh vs. packed vs. ice explains why.)
What this Fairfax 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.
Fairfax 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.