Snow on the Roof: Warning Signs and When to Act

Warning signs that a roof is overstressed

FEMA says overstressed roofs usually give some warning, and that wood and steel structures may sag noticeably before they fail. The signs it lists are:

• Sagging ceiling boards or tiles, or ceiling boards dropping out of their grid.
• Sprinkler lines or sprinkler heads that sag or hang below a suspended ceiling.
• Popping, cracking and creaking noises.
• Roof members that sag, including the plywood sheathing or metal decking.
• Truss bottom chords or web members that bow.
• Doors or windows that can no longer be opened or closed.
• Wood members that have cracked or split.
• Cracks in walls or masonry.
• Severe roof leaks.
• On a low-slope roof, a lot of water collecting where it does not drain.

What to do if you see one

1. Get everyone out. FEMA's wording is that the building should be promptly evacuated.
2. Call for an inspection. Contact the local building authority (your city or county building department), a qualified design professional, or both, and ask for a detailed structural inspection.
3. Do not go up to clear the roof yourself. If anyone is already removing snow and there is any concern that the roof may collapse, FEMA says to stop all removal and evacuate.

Why depth alone does not tell you

The flyer gives no safe depth of snow, and neither does this page. It names four things that put more load on a roof than the snowfall total suggests:

• Drifting and sliding snow. Snow that piles deeper in some places than others puts a high, concentrated load on those parts of the roof.
• Rain on snow. Heavy rain soaks into the snow and can add a great deal of load.
• Melt between storms. If the roof drainage is blocked or poorly maintained, ice dams can form, which load the eaves and stop a sloped roof shedding snow. On flat and low-slope roofs, meltwater can pond in the low areas.
• The shape of the roof. Simple, steep roofs shed snow most easily. Drifts collect in valleys, behind chimneys and equipment, against parapets and where a lower roof meets a higher wall.

So look hardest at the places where snow collects: valleys, the roof below a taller section, around dormers and chimneys, and porch or sunroom roofs under a main roof that can shed snow onto them.

After a heavy snowfall: does the snow need to come off?

FEMA's advice is to ask before you act. A local building authority or a qualified design professional knows the snow conditions in your area and what local buildings are designed to carry under the building code, and can say whether removal is needed. If more snow is forecast, taking snow off sooner lowers the risk from the next storm, and it is less work than removing it later.

If the snow does need to come off, FEMA says the work should only be done by qualified individuals following safety protocols, because roof snow removal is dangerous. For most homeowners that means hiring someone who does this work, not climbing up.

How snow is removed safely

These points are from the flyer's lists for the people doing the work. They are also a useful check on anyone you hire.

• From the ground where possible. In some cases a long-handled, non-metallic snow rake can be used from the ground, which lowers the risk. Metal rakes can damage the roofing and are an electrocution risk, so FEMA says to avoid them.
• Stand clear of the eave. Roof snow can slide at any moment. Keep far enough back to be outside the slide, and watch for icicles coming loose.
• Keep people away below. Have someone on the ground keeping others away from where snow and ice will fall, and move anything that falling snow could damage.
• Do not scrape the roof bare. Removing all the snow can damage the roof covering and lead to leaks. FEMA says to leave at least a couple of inches.
• No sharp tools or machines. No picks and no mechanical snow removal equipment; plastic shovels, not metal ones.
• Drifts first, and keep the load even. Remove drifted snow first, do not pile snow elsewhere on the roof, and on a sloped roof work from the ridge toward the eave if possible.
• Mind where it lands. Keep removed snow away from exits, downspouts, vents and equipment.
• On the roof itself, the work should follow OSHA protocol for rooftop work, with fall arrest harnesses where they apply, and buried skylights and other hazards should be marked.
• Afterwards, have the roofing checked for damage. After a particularly large snowfall, a quick look at the structure is sensible too.

Before winter

Blocked drainage is one of the causes FEMA names, so clear gutters and downspouts in the fall. If ice dams have formed at your eaves before, see how much ice and water shield you need for the membrane that goes under the first courses of shingles, and for paths and steps see how much ice melt you need. The rest of the season's jobs are in the winter home prep planner.

Source: Federal Emergency Management Agency, FEMA Snow Load Safety Guidance flyer (FEMA P-957), read October 12, 2026. The flyer summarizes the full FEMA P-957 Snow Load Safety Guide, which also covers what to do before the snow season. For questions, the flyer gives the FEMA Building Science Helpline, 866-927-2104.

Frequently asked questions