Calvert County, MD Roof Snow Load - 20 psf
What ASCE 7 says about snow load in Calvert County
That's Calvert County's design roof snow load per ASCE 7-22, for a typical heated single-family home - the number a permit reviewer starts from. Flat and low-pitch roofs in Calvert County are actually governed by ASCE 7's §7.3.4 minimum of 20 psf, not the 17.5 psf the ground-load formula alone would produce.
Converted to something you can actually eyeball on a roof: about 44 in. of fresh powder, 16 in. once it settles and packs down, or just 4 in. if it's turned to ice. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
Calvert County in numbers
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#658 of 2,758
- Maryland rank#14 of 21
- Population94,913
- Annual snowfall, NOAA normal13.4 in.
- FIPS24009
Where Calvert County's figure sits nationally
Out of 2,758 rated US counties, Calvert County sits at #658, the top 24% nationally - #14 of 21 within Maryland. Maryland counties average 20.1 psf; Calvert County runs 0.1 psf lower than that.
Near 38.5227°N 76.5298°W, FIPS 24009: Calvert County counts 94,913 residents and a 25 psf map value, which the code's own factors turn into 20 psf.
How much it actually snows in Calvert County
Most winters bring Calvert County roughly 13.4 in. of snow - NOAA's normal at FRANCONIA 1.3 SSE, VA US, 36.3 mi off. 36.3 mi is a real gap between Calvert County and its nearest reporting station, so local snowfall can diverge from this figure, especially near elevation changes. (fresh vs. packed vs. ice explains why.)
Read this before you rely on it
Calvert County's number above is ASCE 7-22's default case, not a custom calculation: ordinary residential occupancy, heated, sited on ground that's neither fully sheltered nor fully exposed. Any one of those changing - pitch, exposure, heating, occupancy - moves the real figure.
Nothing here substitutes for an address-level number. Get one free, in about a minute, from the ASCE 7 Hazard Tool using your own coordinates rather than Calvert County's county-wide figure. Details: the calculation guide.