Climate Guide · Snow + structural
Roof framing is rated for snow load — typically 30, 40, or 50 pounds per square foot (psf) of ground snow load equivalent, depending on jurisdiction and design year. NE ground snow load ranges from 30 psf along the southern coast to 100+ psf in the White Mountains. When framing meets accumulation, math matters.
Building codes specify a design ground snow load (Pg) for every NE county — ranging from 30 psf in coastal RI to 100+ psf in higher elevations of NH and VT. The actual roof snow load is calculated by adjusting Pg with factors for roof slope (steeper = less snow stays), exposure (windswept = less accumulation), and importance (hospitals require higher safety factors). The result is the per-square-foot load your framing was designed for.
Fresh fluffy snow weighs about 7 pounds per cubic foot. Settled snow: 15 lbs. Wet packed snow: 20 lbs. Ice: 57 lbs. So 4 feet of fresh fluffy snow is about 28 psf — well within most framing capacity. But 4 feet of accumulated wet snow with ice layers underneath can easily exceed 60 psf, which gets close to or over the design rating for older NE homes.
Risk factors: low-pitch additions (porches, mudrooms, sheds) on older homes where the addition was built to a lower standard than the main house. Sagging ridge lines visible from the ground. Homes built before 1960 that have been added onto multiple times. Mountain NH and VT homes in the highest snow-load zones. Homes with extensive cathedral ceilings (less interior reinforcement than truss-framed attic spaces).
Sagging ridge or rafters visible from the attic. Cracking sounds during heavy snow. New cracks in interior drywall above doorways or windows (an indicator of framing flex). Doors that stop closing properly during a heavy snow event. Any of these = call a roofer and a structural engineer immediately.
Do: remove the first 3–6 feet of snow from the eave with a long-handled roof rake (not by climbing on the roof). Do: clear paths under valleys where snow shedding accumulates. Don’t: climb a snowy roof. Don’t: use sharp tools to chip ice. Don’t: assume the framing is fine because the house hasn’t fallen down — sustained over-load damages framing over years before it fails catastrophically.
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