Snow Load on Your Roof: When to Worry

Roofs are designed for snow, up to a point

Every roof is built to carry a design snow load set by the local building code, and in western Montana that number can change a lot with elevation. A cabin up a drainage may be built for far more snow than a house in town a few miles away. Your city or county building department sets the requirement for your address.

Trouble usually comes from conditions the roof wasn't planned for. FEMA's Snow Load Safety Guide points to:

• Drifting and sliding snow piling up unevenly, for example on a lower roof below a higher one, or behind a chimney.
• Rain on snow, which soaks the snowpack and makes it much heavier.
• Melting and refreezing between storms, including ice dams that hold snow and water at the eaves.
• Complicated roof shapes with valleys, dormers, and steps where drifts collect.

Warning signs of an overloaded roof

FEMA and the U.S. Department of Energy's Building America program list these warning signs:

• Sagging ceilings or roof lines, or a ridge that's no longer straight.
• Popping, cracking, or creaking sounds from the roof or attic.
• Doors or windows that suddenly stick or won't close.
• New cracks in walls, ceilings, or masonry.
• Cracked or split rafters or trusses, if you can safely see the attic.
• Severe leaks.

If you see these signs, get everyone out of the building and contact your local building department or a structural engineer, as FEMA advises. Then call us at 406-210-3168. We take emergency calls and messages 24/7.

Clearing snow safely

• Use a roof rake from the ground where you can, and keep ladders and tools clear of power lines.
• Leave a few inches of snow on the roof instead of scraping down to the roofing, which can damage shingles and metal.
• Use plastic tools, not metal, and work with a helper on the ground.
• If the roof is sagging or creaking, don't go up. Your weight adds to the load.
• On metal roofs, remember that snow can slide all at once. Keep people, pets, and cars out from under the eaves.

Plan ahead: snow guards, slopes, and heat loss

Good roof design helps the roof deal with snow. Metal roofs shed snow, so we plan where it lands and add snow guards over doors, decks, and walkways. Shingle roofs hold snow, so the attic needs to stay cold to avoid the melting and refreezing that builds ice dams and extra weight at the eaves. Uneven melt on your roof is often a sign of heat loss; read what snow melt patterns say about your attic.

How Revive helps

After a heavy winter, or before one, we inspect the roof and attic for sagging, damaged framing we can see, leaks, ice dam damage, and insulation and ventilation problems. If we see signs of a structural issue, we'll tell you plainly and recommend an engineer. We are roofers, not structural engineers.

Sources

• FEMA P-957: Snow Load Safety Guide
• U.S. DOE Building America Solution Center: Managing Snow Loads on Roofs and Decks
• Mass.gov: Roof collapse and snow removal safety

Sources are public pages we checked on November 13, 2026. This guide is general information, not engineering, insurance, or legal advice.