Snow Load on Roofs: Warning Signs and Safe Snow Removal

A foot of light, dry snow weighs about 3 pounds per square foot, a foot of wet, heavy snow about 21, and a foot of ice about 57, according to FEMA. Depth alone does not tell you whether a roof is overloaded; the type of snow, any ice beneath it, and the house’s own warning signs do.

So the useful questions are how heavy this particular snow is, what the roof was built to carry, and whether the house is showing strain. If it is, the estimate stops mattering and the answer is to get people out from under that part of the roof.

Why the Same Depth of Snow Can Weigh Very Different Amounts

FEMA’s Snow Load Safety Guide (P-957), published in January 2013, gives the range: “The weight of 1 foot of fresh snow ranges from 3 pounds per square foot for light, dry snow” up to about 21 pounds per square foot for wet, heavy snow. It adds that “1 foot of ice weighs approximately 57 pounds per square foot.” Those figures are weight per square foot of roof for each foot of depth, not a density you can apply to packed or drifted snow, and FEMA gives no separate figure for packed snow.

The spread comes from water content. Fluffy snow is mostly air. Wet snow, snow that has settled over several storms, and snow that has soaked up rain all hold more water in the same depth. Ice is the extreme case: FEMA’s guide says “One inch of ice weighs a little less than 5 pounds per square foot,” so a thin layer under the snow can outweigh several inches of powder above it.

That is why the same roof can be fine under deep powder in January and struggle with less snow after a March rain. Ice under the snow, such as the ridge an ice dam builds at the eaves, adds the heaviest material of all at the edge of the roof.

A Rough Load Estimate and What to Compare It To

Read this section as arithmetic about the snow, not a safety check on the roof. It can tell you roughly how heavy the snow is; it cannot tell you the roof will hold it. If any warning sign in the next section is present, leave the rooms below first and skip the calculation.

You can estimate the load from the ground with a yardstick, a note of what the snow is like, and FEMA’s figures:

Estimated load (psf) = (snow depth in feet × weight per foot for that snow) + (ice thickness in feet × 57)

Use 3 for light, dry snow and 21 for wet, heavy snow, and pick a value between them for snow in between. Measure depth on a flat, open surface near the house, then look at the roof: drifts behind chimneys, in valleys and on lower roofs below a higher one collect more than the ground does. FEMA notes that snow weight on the ground is not the same as the load on a roof, so treat the result as a rough number.

To judge the snow type, lift a shovelful. Light, dry snow barely registers; wet, heavy snow makes you want to set the shovel down. If rain has fallen on the snowpack, use the wet-snow value of 21 even if the snow was light before the rain. That errs on the heavy side, the safe direction for a rough check, but it cannot tell you how much water the snow absorbed, so treat rain on deep snow as a reason to clear snow or call for help sooner.

Hypothetical example: a roof carries 2 feet of wet, heavy snow over 2 inches of ice. Snow: 2 × 21 = 42 psf. Ice: (2 ÷ 12) × 57 = 9.5 psf. Estimated load: about 51.5 psf. The same depth of light, dry snow over the same ice would be about 15.5 psf. The depth did not change; the weight more than tripled.

Then compare the estimate to what the roof was designed to carry:

• Manufactured homes. HUD’s construction rule, 24 CFR 3280.305, current on eCFR as of October 22, 2026, requires roofs designed for live loads by zone: 40 psf in the North zone, 30 psf in the Middle zone and 20 psf in the South zone. The data plate inside the home shows the zone; HUD requires it to “include reproductions of the Load Zone Maps.” For more on these roofs, see manufactured and mobile home roofing.
• Site-built homes. Design snow loads are set by the code your local jurisdiction adopted and vary by location and elevation. Ask your local building department for the design roof snow load used in your area, and remember that an older house, an altered roof or damaged framing may not carry it.

An estimate that comes close to the design figure is a reason to act. An estimate well below it is not a guarantee, because rot, prior damage or undersized framing can lower what a roof will actually hold.

Warning Signs of an Overstressed Roof

The house tells you more than any formula. FEMA’s P-957 lists these warning signs:

• “Sagging roof members, including metal decking or plywood sheathing”
• “Popping, cracking, and creaking noises”
• “Doors and/or windows that can no longer be opened or closed”

Check from inside. Look along ceilings for a new dip or bow, especially near the middle of a span or below a valley. Try interior doors on the top floor, which can bind when the framing above them deflects. Listen from the top-floor rooms during the heaviest part of the storm.

If you see or hear any of these signs, get everyone out of the rooms under that part of the roof, or out of the house if you cannot tell how far the strain reaches, and keep them out. Then call a structural engineer or your local building department, and call 911 if a ceiling is visibly moving or cracking. Do not go into the attic or onto the roof to look more closely. Once everyone is safe, read the full FEMA guide before the next storm; DOE’s summary of the FEMA guide notes that it covers “actions that should be taken before, during, and after a snow event.”

A dip that is still there after the snow melts is a different question. The guide to a sagging roof explains what a lasting sag in the deck or framing means. If the same storm also tore shingles or dropped a limb on the house, checking a roof after a storm sets the order of first steps.

Removing Snow From the Ground Without Damaging the Roof

FEMA’s guidance is to remove snow from the ground where you can: “Snow removal can be conducted from the ground, removing the risk to people on a hazardous roof.” On steep roofs, it advises using “a non-metallic snow rake … if possible.” When the snow load is close to what the roof can carry, FEMA says snow removal “should be performed by a licensed, insured professional roofing contractor who has experience in removing snow from roofs.”

Raking from the ground still has costs. University of Minnesota Extension’s guide to dealing with ice dams notes that a roof rake and push broom “can be used to remove snow, but may damage the roofing materials.” A blade dragged hard across shingles can strip granules and catch tab edges. Pull the snow down in strips from the eave upward, and leave a thin layer on the roof rather than scraping to the shingle surface.

Work safely while you do it:

• Stand clear of the snow you are pulling down; a slab sliding off the roof can knock you over.
• Keep the rake and its handle well away from the electrical service line where it reaches the house.
• Do not use a ladder to reach higher snow. If you cannot reach it from the ground, it is a job for a crew.
• Leave ice at the eaves alone. Breaking it damages shingles and gutters; safe ways to deal with ice at the eaves covers what to do instead.

Low-slope and flat sections are the hardest case. They cannot be raked well from the ground, they hold snow longer than steep slopes, and they are where drifts from a higher roof land. If one of those sections is carrying heavy snow, that is the part of the house to hire out first. If you hire a removal crew, ask for a certificate of insurance and check it before anyone goes up; the guide to checking a roofer’s license and insurance explains what to look for.

If snow sliding off a metal or steep roof is the problem, rather than weight, snow guards are the hardware that holds it in place.

When to Rake, When to Hire, and When to Get Out

Get out first if the house shows any FEMA warning sign: sagging members, popping or cracking noises, or doors and windows that no longer open or close. People leave the rooms below, and the calls come after.

Hire a licensed, insured roofing contractor when your estimate approaches the design load you were given or the zone on your data plate, when the roof is low-slope or out of reach from the ground, or when rain is forecast on top of heavy snow. Rake from the ground yourself when the lower edge is reachable, the snow comes away with the rake and the house shows no strain.

An estimate below the design load is not proof that the roof is safe. The arithmetic is a rough average: drifts, snow sliding from a higher roof, ice at the eaves and earlier damage to the framing can overload one section while the average looks low. Use the number only to decide when to clear snow or hire help sooner. Whether the roof can carry what is on it, and whether to stay in the house, is a call for a structural engineer or your local building or emergency officials, and the warning signs override any estimate.

Check top-floor doors and ceilings for the warning signs now, measure the snow and note whether it is light or wet, and if you live in a manufactured home, find the roof load zone on the data plate before the next storm.

This guide is general information for U.S. homeowners, not legal, insurance, tax, or engineering advice. Codes, laws, and policy terms vary by location and change over time; confirm details with your local building department, your insurer, or a licensed professional.

Sources

• Snow Load Safety Guide, FEMA P-957, Federal Emergency Management Agency
• 24 CFR 3280.305, Structural design requirements, Office of the Federal Register (HUD regulation)
• FEMA P-957 Snow Load Safety Guide, U.S. Department of Energy Building America Solution Center
• Dealing with and preventing ice dams, University of Minnesota Extension