New Castle County, DE Roof Snow Load - 20 psf
How much snow is too much for a roof in New Castle County, DE?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in New Castle County to carry. ASCE 7's low-slope-roof minimum (§7.3.4) raises the governing figure to 20 psf - higher than the 14 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. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
New Castle County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#533 of 2,758
- Delaware rank#1 of 3
- Population588,093
- Annual snowfall, NOAA normal11.8 in.
- FIPS10003
How New Castle County compares
20 psf ranks #533 of 2,758 US counties with a mapped snow load (top 19%) - and #1 of 3 in Delaware. New Castle County's figure lands almost exactly on Delaware's own county-average of 20 psf.
Population 588,093 (FIPS 10003), roughly 39.5759°N 75.6441°W. The 20 psf ground snow load ASCE 7-22 maps here becomes 20 psf once the code's own design factors are applied.
Typical snowfall in New Castle County, DE
NOAA's 30-year normal for New Castle County: 11.8 in. of snow a year, from the SEABROOK FARMS, NJ US station. (fresh vs. packed vs. ice explains why.)
What this New Castle 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.
New Castle 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. (How this figure is calculated.)