Mercer County, NJ Roof Snow Load - 20 psf
How much snow is too much for a roof in Mercer County, NJ?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Mercer 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. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
Mercer County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#551 of 2,758
- New Jersey rank#12 of 17
- Population392,138
- Annual snowfall, NOAA normal26.6 in.
- FIPS34021
How Mercer County compares
20 psf ranks #551 of 2,758 US counties with a mapped snow load (top 20%) - and #12 of 17 in New Jersey. That's 0.1 psf below New Jersey's own county-average design load of 20.1 psf.
Population 392,138 (FIPS 34021), roughly 40.2825°N 74.7037°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 Mercer County, NJ
NOAA's 30-year normal for Mercer County: 26.6 in. of snow a year, from the EWING TWP 0.8 ESE, NJ US station. (fresh vs. packed vs. ice explains why.)
What this Mercer 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.
Mercer 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.