Start clearing snow from a commercial roof when the load reaches about half of what the roof was designed to carry. On some roofs that can happen with as little as 6 inches of heavy, wet snow or ice, so judge it by weight, not depth. The work should be done by a trained crew using OSHA fall protection.
This guide covers when and how snow should come off, the warning signs that mean get people out now, and how to protect a roof from snow and ice with a fall maintenance checklist.
Why Is Commercial Roof Snow Removal Important?
Removing snow keeps the weight on a roof below its design load, the most weight it was built to carry safely. Most commercial roofs are designed for roughly 15 to 40 pounds per square foot, and older buildings or roofs with added equipment can have less margin.
Snow adds up faster than most people expect. A foot of fresh snow weighs about 3 pounds per square foot when it’s light and dry and up to 21 pounds when it’s wet and heavy, and one inch of ice weighs close to 5 pounds per square foot. A foot of wet snow on a 10,000-square-foot roof can add well over 100,000 pounds.
Too much weight can crack or deflect the deck, open leaks, send snow sliding off sloped sections onto walkways, and shut down part of the building. In the worst case, a roof collapses and seriously injures the people inside.
When Should Snow Be Removed from a Commercial Roof?
Don’t wait for the roof to show stress. Start clearing when the snow load reaches about 50 percent of the roof’s design capacity. On a roof with a low design load, wet snow or ice can get there in as little as 6 inches, while dry, fluffy snow may take more than a foot.
Watch the drifts. Wind piles snow against parapets, rooftop units, roof steps, and the walls of taller buildings next door, so one area can carry several times the load of the rest of the roof. If you don’t know your roof’s design load, it’s usually listed in the general notes of the structural drawings, or a structural engineer can determine it.
Warning Signs That Need Attention Now
These are signs a roof may be overloaded. If you notice any of them, get people out of the affected area first. Then call a structural engineer and your roofing contractor right away, and don’t send anyone onto the roof until it has been evaluated:
- Sagging roof deck, beams, or ceilings
- Sprinkler heads, pipes, or conduit at the ceiling that look bowed or pushed down
- Doors or windows that suddenly stick or won’t open or close
- Popping, cracking, or creaking sounds from the roof structure
- Water ponding in spots on the roof that normally drain
- New leaks or ceiling stains during or after a storm
Heavy icicles over doors and walkways aren’t a structural warning, but they are a falling hazard. Keep people clear and have them removed safely.
GSM’s emergency line, 800-532-ROOF (800-532-7663), is staffed 24 hours a day, 365 days a year. For critical emergencies we dispatch a crew immediately, with a response target inside four hours. You can also request emergency roof repair online.
Why Can’t I Take Care of Commercial Roof Snow Removal Myself?
Roof snow removal combines fall hazards, heavy loads, and roof surfaces that are easy to damage, so it should be done by a trained crew working under OSHA fall protection. Sending your own maintenance staff up puts both the people and the roof at risk:
- Damage to shingles, ballast, membrane, flashing, or gutters
- New leaks from punctures and torn seams
- Uneven removal that overloads one section of the roof
- Falls from roof edges, ladders, or aerial lifts, and falls through skylights hidden under snow
- Shock and electrocution from damaged extension cords and contact with power lines
- Overexertion injuries, hypothermia, and frostbite
Skylights and roof openings can disappear under snow, and falls through them are often fatal. Anyone working on the roof must be protected under OSHA fall protection rules, and a violation can bring citations and fines on top of the injury risk. That’s why GSM’s snow removal crews work under OSHA fall protection on every job.
How Is Snow Safely Removed From a Flat Commercial Roof?
A trained crew checks the load first, sets up fall protection, and removes snow evenly so no part of the roof is left overloaded. A safe removal follows this order:
- Evaluate the snow load and mark drifts, drains, skylights, vents, and roof edges before anyone starts shoveling.
- Set up OSHA fall protection and rope off the drop zones below so no one walks under falling snow.
- Clear the heaviest drifts first, then work evenly across the rest of the roof. Snow should never be piled up somewhere else on the roof.
- Use plastic shovels and push tools, not metal, and keep picks and mechanical equipment off the roof surface.
- Leave about 2 inches of snow on the membrane so tools never touch the roof.
- Clear ice from drains, scuppers, and gutters so meltwater can drain.
GSM’s Roof Snow Removal Plan
Every GSM snow removal job starts with a checklist: the crew evaluates the snow load, finds where the weight is concentrated, identifies hazards like skylights and roof edges, and chooses the fall protection equipment for that roof. GSM has removed snow from flat and steep-slope commercial roofs for decades.
Watch a GSM crew clear snow from a Walmart roof.
To line up snow removal before the next storm, call 800-532-ROOF or request our snow removal services. Have the building address, roof type, and approximate snow depth ready. We’ll evaluate the snow load first, then plan the removal.
How Do Snow and Ice Damage a Flat Commercial Roof?
Snow load gets the headlines, but many winter leaks on flat and low-slope roofs start with water that can’t drain and then freezes. These are the problems we see most often from December through March:
- Ice at drains, scuppers, and roof edges. On a flat roof, meltwater refreezes at drains, scuppers, and parapet walls, and the ice blocks drainage so the next melt backs up under flashing and through laps in the membrane. Here’s why a flat roof can leak when it snows but not when it rains.
- Ice dams on sloped sections. Heat escaping through the roof melts snow from below, and the water refreezes at the colder edge. The ridge of ice traps water behind it, and that water works its way under shingles, slate, or metal panels.
- Freeze-thaw damage. Water that gets into an open seam, a cracked flashing, or a split in the membrane freezes and expands. Each cycle opens the gap a little wider, which is why a small fall problem can be an active leak by February.
- Clogged drains and gutters. Leaves and debris left over from fall freeze into a dam. Water ponds behind it, adds weight to the deck, and sits on the membrane until it finds a weak spot.
- Cold, brittle roofing. TPO and PVC membranes stiffen and puncture more easily in the cold, and built-up and modified bitumen roofs get brittle, which is one more reason shovels and foot traffic need to be controlled.
Repairing Winter Weather Damage
After a major storm, keep people off the roof until it has been checked. Look for new ceiling stains, confirm the drains are flowing, and photograph any damage with the date and snow depth for your insurance file. On the roof, a contractor will check for shovel punctures, split seams, loose flashing, damaged drains, and wet insulation. Many adhesives and sealants have minimum application temperatures, so a winter repair is sometimes a temporary fix that holds until warmer, drier weather allows the permanent one. Learn about our commercial roof repairs.
How to Protect Your Roof Against Snow and Ice
- Keep drains, scuppers, and gutters clear going into winter and after every major storm, so meltwater has a path off the roof.
- Fix wet or missing insulation. It lets heat escape and melt snow from below, which starts the melt and refreeze cycle. On steep-slope sections with an attic, poor ventilation does the same thing.
- Remove heavy snow before it melts and refreezes, especially around drains and along the low edges of the roof.
- Don’t chip ice off the roof surface. Picks, metal shovels, and ice choppers puncture membranes and crack slate and shingles. Check with the membrane manufacturer before using salt or other deicers.
Winter Roof Maintenance Checklist for Snowy Climates
Most of the problems above start as small defects that cost far less to fix before freezing weather. Before the first snow, work through this checklist with your roofing contractor:
- Schedule a professional inspection of seams, flashing, penetrations, and rooftop equipment curbs to find hidden damage and weak points before freezing weather arrives. Learn about our commercial roof inspections, including infrared scans.
- Clear drains, gutters, scuppers, and downspouts of leaves and debris, and confirm water flows freely off the roof and away from the building.
- Check for wet insulation. Wet insulation loses its insulating value, raises heating costs, and feeds the melt and refreeze cycle. An infrared scan can find it under the membrane without cutting into the roof, but it needs a dry, snow-free roof, so fall is the time to do it.
- Trim overhanging trees and branches. Branches loaded with snow and ice can snap and puncture the membrane.
- Repair open seams, loose flashing, and small leaks now. Snow and freeze-thaw cycles will turn each one into a larger problem.
- Set up a snow removal plan before you need it. Know your roof’s design load, who you’ll call, and where snow can be safely dropped from the roof.
The National Roofing Contractors Association recommends inspecting roofs at least twice a year, preferably in spring and fall, and again after severe weather. Our guide to spring and fall roof maintenance covers what each visit should check. The fall visit covers most of this checklist in one trip. GSM’s Exceptional Roof Protection Plan schedules both visits, and each one clears drains, gutters, and scuppers and ends with a written inspection report and pricing for any repairs. Plan customers also get leak calls acknowledged within one business hour and a crew onsite within two business days, or the repair is no charge.
Snow on the roof right now? Call 800-532-ROOF (800-532-7663) any time, day or night. Getting ready for winter? Ask about a fall inspection or the Exceptional Roof Protection Plan. GSM Roofing has served commercial buildings in Pennsylvania, New Jersey, Delaware, and Maryland since 1946.
Commercial Roof Snow and Winter FAQs
How do I know if there’s too much snow on my commercial roof?
Compare the estimated snow load to the roof’s design load and start removal at about 50 percent. Wet snow and ice weigh far more than dry snow, and drifts concentrate weight in one area, so depth alone can be misleading. Sagging, creaking, and doors that stick are late warnings that mean evacuate the area and call a structural engineer. Some facilities install roof snow load sensors that send an alert when the weight approaches a set limit.
How do I find my roof’s design load?
It’s usually listed in the general notes of the building’s structural drawings. If you can’t find it, a structural engineer can determine it. Older buildings, and roofs that have had equipment or extra reroof layers added, may have less capacity than you’d expect.
Can our own maintenance staff shovel the roof?
We don’t recommend it. Shovels and picks damage membranes, flashing, and shingles, and roof edges, skylights hidden under snow, and icy surfaces cause serious and sometimes fatal falls. Anyone working on the roof must be protected under OSHA fall protection rules.
What should I do after a major snowstorm?
Keep people off the roof until it’s been checked, look for new ceiling stains, confirm the drains are flowing, and photograph any damage with the date and snow depth for your insurance records. Then have a roofer inspect for punctures, split seams, loose flashing, and wet insulation.
Can winter roof damage be repaired in cold weather?
Often, yes, at least temporarily. Leaks can be stopped in winter, but some permanent repairs need dry conditions and minimum temperatures for adhesives and sealants, so the final fix may wait for a warmer day. GSM’s emergency line, 800-532-ROOF, is answered 24 hours a day, 365 days a year.
When should I schedule winter roof maintenance?
In the fall, before the first snow. The National Roofing Contractors Association recommends inspecting roofs at least twice a year, preferably in spring and fall, and the fall visit clears drains and fixes open seams and loose flashing before freeze-thaw cycles turn them into leaks.