Flat and low-pitched roofs carry the greatest risk of buckling under heavy snow and ice. Massachusetts guidance says clear from the ground with a plastic shovel or snow rake, leave two to three inches on the shingles and stay off the roof. Sagging, severe leaks or doors that pop open mean you leave the building and call 911.
Key takeaways
- Flat and low-pitched roofs carry the greatest risk of buckling under heavy snow and ice.
- Massachusetts guidance says to leave about two to three inches of snow rather than scrape to the shingles.
- Standing on a snowy roof and using heat tools are both advised against.
- Sagging roofs, severe leaks, cracked wood members and doors that pop open mean leaving the building and calling 911.
- Nor'easters bring heavy, wet snow and gale-force winds in the season from September to April.
- Snow feeds ice dams, so clearing it helps briefly, but the lasting cure is air sealing, insulation and ventilation.
Which roofs carry the most snow risk?
Flat and low-pitched roofs face the greatest risk of buckling under heavy snow and ice. The state names industrial buildings first, though some homes have such roofs too.
Snow weighs most where it can sit. A steep roof sheds much of its snow as it builds, while a flat or low-pitched section holds the load until the structure is asked to carry more than it was built for. The state's roof collapse guidance says these roofs carry the greatest risk, mostly on industrial buildings and sometimes on homes. Snow on a flat section does not slide off the way it does from a steep slope, so the weight stays where it lands until it is cleared or melts.
On a house, the low-slope pieces are the ones to check first: additions, rear sections, dormers and porch roofs that were built nearly flat. The steep main roof may be fine while one of these sections struggles, so look at the low parts after a heavy storm and note any sag or movement. The flat roof repair page covers the seams and drains that tend to fail on these sections.
How much snow should stay on the roof?
State guidance says to leave about two to three inches of snow on the roof rather than scraping down to the shingles. Scraping to the covering can damage it, so the state advises against it.
The state's roof collapse page advises using a plastic shovel or a snow rake and leaving about two to three inches rather than scraping to the shingles. The reason is practical: metal blades cut and lift the shingle surface and edges, and that damage can show up later as leaks. A plastic tool and a light touch do less harm to the covering.
Clear from the ground or from a secure position that keeps you off the roof. A roof rake that reaches the eave is the usual tool. Work from the outside edge inward, and do not chase every trace of snow. The goal is to lighten the load and protect the covering, not to bare the roof. Work in short passes, check the covering as you go, and stop if the shovel starts catching on the shingles.
What should you avoid on a snowy roof?
Do not stand on a snowy roof, avoid ladders on snow-covered ground and do not use heat tools to clear ice. Do not place heavy equipment on the roof unless a registered professional engineer approves it.
The state advises avoiding ladders and heat tools around snowy roofs. A ladder set on snowy, icy ground can slip, and a person on a sloped surface can lose footing in seconds. Heat tools such as torches and heat guns can start fires in dry debris and can soften and damage the covering. The safer path is a long tool used from the ground. A slip from a roof edge is a fall, and a fall from a low roof onto ice can still cause serious injury.
Do not stand on the roof, and do not put heavy equipment there, including a generator or stacked material, unless a registered professional engineer approves the load. Roof access in winter is work for someone with the right equipment and training, so a homeowner's first move should be to call a technician rather than to climb.
What warning signs mean the roof is failing?
Sagging roofs, severe leaks, cracked wood members and doors that pop open are the state's warning signs of structural trouble. Leave the building and call 911 from outside.
The state lists sagging roofs, severe leaks, cracked wood members and doors popping open as signs of structural trouble. Any one of them is reason to leave, not to investigate further. A roof that is bowing, or a ceiling that is cracking under snow, is past the point of a homeowner's own assessment. These signs matter because they can appear when the framing is already under stress, so waiting to see whether they get worse is the wrong test.
Leave first, then call 911 from outside, and keep people and pets away from the affected area. Once emergency services have cleared the building, a roofer or a structural engineer can assess the damage. Keep notes of what was seen and when, and any photographs taken from a safe distance, because they will matter later for repairs and for any insurance claim.
Why does the storm track matter for snow?
A nor'easter brings heavy, wet snow and gale-force winds during the September-to-April season. The heaviest snow usually falls north and west of the storm's track, which is the central Massachusetts load case.
A nor'easter is a strong low-pressure system that affects the Mid-Atlantic and New England and forms over land or coastal waters. The National Weather Service says these storms nearly always bring heavy rain or snow and gale-force winds, and that they are most frequent and most violent from September through April. That season covers the months when snow is most likely to build up on a roof.
The NWS notes that the heaviest snow usually falls north and west of the surface low's track, and that it is typically heavy and wet. Wet snow weighs more than dry powder, and gusts add to the load on the edges. That combination is what central Massachusetts roofs have to be ready for, so check after each storm rather than waiting for the thaw.
How does snow tie into ice dams?
The snow that loads a roof is the same snow that melts into ice dams. Clearing the excess can reduce the water that feeds a dam, but it does not fix the heat loss underneath.
The same snow that loads a roof also feeds ice dams. When the upper snow melts over a warm attic, water runs to the cold eave and freezes. Clearing excess snow from the lower roof, carefully and from the ground, can reduce the water that feeds a dam. It is a short-term measure and no substitute for air sealing and insulation, which the ice dams guide covers in full.
Gutters have to be clear for any melt to leave. The state's ice dam guidance starts with clearing gutters before winter so meltwater can drain instead of backing up. Clear the gutters, then clear the excess snow from the lower roof, and leave the rest for a planned visit rather than a rushed one in the middle of a storm.
Do steep roofs shed snow on their own?
Steeper roofs shed snow as it builds, but that snow can slide onto people, cars and doorways below. The drop zone matters as much as the roof.
A steep covering sheds snow as it accumulates, which keeps the load down on the roof itself. The trade-off is what lands below. A sliding sheet of snow can strike a person, a car or a doorway, and it can pile against a wall or into a gutter. Know where the snow will come off before it does, and keep that area clear. Snow that slides off in one piece can be far heavier than it looks from the ground, so treat the drop zone as a hazard during a thaw.
If a roof sheds onto an entry or a driveway, the snow is a hazard and needs managing from the ground. Snow guards and planned clearing are common answers, and a roofer can say which fits the roof. Some roofing systems, such as metal roofing, are designed with snow retention in mind for exactly this reason.
When should you call a technician?
Call a technician when a roof has sagged, is leaking heavily or shows damage you cannot reach safely. A technician can check the framing and the decking from the attic before any work is planned.
Call early, before the roof reaches a warning sign. A technician can look at the load on the roof, check the decking from the attic and say which sections need attention. Call (833) 751-2102 to reach a technician, and the line is answered around the clock.
After a storm, check the attic for wet insulation, look at the gutters for ice ridges and inspect the low-slope sections. Record what you see, keep it dated and take photographs from the ground. That record helps the roofer, the building department and any insurer, and it helps you decide whether a roof can wait for a clear day.
Frequently asked questions
What is the snow load on my roof?
This guide prints no snow load figure. The code sets a ground snow load town by town, and the building department confirms the figure for an address. Ask the department before adding anything heavy to the roof, such as stored material or equipment.
Should I shovel my roof down to the shingles?
No. The state advises leaving about two to three inches rather than scraping to the shingles, because metal tools can cut and lift the covering. Use a plastic shovel or a snow rake from the ground. A layer left in place is easier on the covering than a scraped one.
Can I get on the roof to clear snow?
The state advises against standing on a snowy roof and against heat tools. Ladders on snow-covered ground can also slip. Clear from the ground where you can, and call a technician for any work that needs access to the roof itself.
What do I do if I see sagging?
Leave the building first, and call 911 from outside. Sagging roofs, severe leaks, cracked wood members and doors popping open are the state's warning signs of structural trouble. Do not go back in to investigate. Once emergency services have cleared the building, a technician or engineer can assess the damage.
Are flat roofs at more risk than sloped roofs?
Yes. The state names flat and low-pitched roofs as the greatest risk of buckling under snow and ice, mostly on industrial buildings and sometimes on homes. Steep roofs shed snow as it builds, though what lands below still needs managing. Check the low sections first after a heavy storm.
Do snow repairs need a permit?
Work that alters or repairs a structure generally needs a building permit under 780 CMR. The building official decides what counts as an ordinary repair, so ask the Department of Inspectional Services before the work starts rather than assuming an exemption.
Sources
This guide is general information for Worcester County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.