Every winter, after the first real storm, the same question comes up in New Hampshire driveways and kitchen windows: is that much snow on the roof a problem? The honest answer is that it depends, and the thing it depends on is usually not what people expect. Most homeowners judge their roof by how deep the snow looks. Roofers, and the engineers who design roofs, think about how much that snow weighs. Six inches of wet snow can weigh as much as several feet of dry powder, so the number you see from the yard is often the wrong number. This guide explains how snow weight works, what New Hampshire roofs are built to handle, the warning signs worth taking seriously, and what is safe to do yourself versus what belongs to a professional.
Why Weight Matters More Than Depth
Snow is mostly air, and the amount of air varies enormously. Fresh, fluffy powder is light. Snow that has been rained on, packed by wind, or compressed under its own weight is far heavier, even if it looks like less.
A useful way to think about it is water content. Every inch of water held in the snow adds roughly five pounds to every square foot of roof. A foot of light powder might hold an inch of water or less. A foot of wet, heavy snow can hold several. Here is a rough guide to how different types of snow compare:
| Type of snow | Approximate weight per foot of depth | What it means for your roof |
|---|---|---|
| Fresh, fluffy powder | About 3 to 5 pounds per square foot | Looks like a lot, weighs little |
| Damp, freshly fallen snow | About 7 pounds per square foot | Moderate weight, melts and settles quickly |
| Settled snow | About 15 pounds per square foot | Weight builds as it compacts over days |
| Wind packed snow | About 20 to 25 pounds per square foot | Dense, and uneven drifts concentrate the load |
| Wet, heavy or rain soaked snow | 25 pounds per square foot or more | The most concerning type for your roof |
These figures are approximate and vary from storm to storm, but the pattern is reliable. The same snow gets heavier the longer it sits, and it gets much heavier when rain falls on it. One more useful comparison: an inch of solid ice weighs about as much as a foot of packed snow, which is why thick ice on a roof deserves more attention than it looks like it needs.
What Your Roof Is Actually Built to Handle
There is no single number that applies to every New Hampshire roof, and anyone who gives you one without asking about your house is guessing. What exists instead is a system. Building codes are tied to a figure called the ground snow load, which is the weight of snow the code expects on flat, open ground in your town. The roof design load is then calculated from that figure, adjusted for the shape of the roof, how exposed it is to wind, and how much heat escapes through it.
The ground snow load figures used in New Hampshire come from a study by the U.S. Army Corps of Engineers, and the state building code points to that work. Here are values for several towns:
| Town | Ground snow load | Elevation used |
|---|---|---|
| Bedford | 70 pounds per square foot | 700 feet |
| Manchester | 70 pounds per square foot | 500 feet |
| Concord | 70 pounds per square foot | 600 feet |
| Merrimack | 60 pounds per square foot | 400 feet |
| Conway | 95 pounds per square foot | 900 feet |
Two things are worth understanding about these numbers. First, ground snow load is not the weight your roof carries. For a typical heated home with a standard roof, the design roof load works out to somewhat less than the ground figure, often around 70 percent of it, before other adjustments. Second, elevation matters. The Concord building department notes that the figure changes by about 2.1 pounds per square foot for every 100 feet of elevation difference, so a property on a hill can have a meaningfully different value than one in a valley. Your town building department can tell you the exact figure for your address.
You may also see 40 pounds per square foot quoted as a typical New Hampshire roof capacity. That was the common design standard for decades, and it is still a reasonable rough benchmark for older homes. Current code is tied to the local ground snow load instead, which is higher in most of southern New Hampshire.
The catch: older homes
Design numbers describe what a roof should handle if it was built to the standard of its day and has been maintained since. That is not true of every house. A New Hampshire structural engineer has written that many buildings constructed between 1970 and 2000 do not meet even the old 40 pound standard, and that inspections regularly turn up roof framing with a safe capacity well below that. Rot, past water damage, cut or altered rafters, and renovations that removed supports can all reduce what a roof can carry.
This does not mean older roofs are in danger every winter. Most are fine. It means the age and condition of your house matter more than any chart, and it is a good reason to take warning signs seriously instead of assuming the code number will protect you.
Warning Signs Your Roof Is Carrying Too Much
Your roof and house usually give you signals before something goes wrong. After a heavy storm, or a storm followed by rain, pay attention to the following:
- Creaking, cracking, or popping sounds. Noises from the roof, attic, or upper floor ceilings can mean framing is under stress.
- Doors and windows that suddenly stick. Interior doors or windows that were fine yesterday and jam today can indicate that the structure is shifting under load.
- New cracks in drywall or ceilings. Especially cracks that run along a wall and ceiling joint or appear near the middle of a room.
- Visible sagging. A dip in the roofline or a ceiling that looks like it is bowing downward.
- New leaks or water stains. Heavy snow, ice, and melt can force water under shingles even when the roof was dry for years.
- Large ice buildup along the eaves. Thick ice at the roof edge is both a weight problem and a leak risk.
If you notice several of these at once, or a sagging roof or ceiling, treat it as urgent. Move out of the affected area, and call a professional instead of trying to investigate from underneath it.
A Practical Rule of Thumb for When to Remove Snow
Because roofs vary so much, roofers rely on a conservative rule of thumb instead of a code number. Many in the industry use about 20 to 25 pounds per square foot as the point where it is worth thinking about removing snow from an average residential roof. This is a practical trigger, not a building code limit, and it is intentionally cautious because so many existing roofs are older than the current code.
For a sense of what that looks like, roughly 20 pounds per square foot is about four feet of fresh powder, about two feet of packed snow, or about a foot of heavy wet snow. Those numbers are why depth alone is so misleading. A foot of wet snow after a rainy storm can be more of a concern than two feet of powder.
A simple way to estimate is to press a ruler or yardstick into the snow in several spots on a roof you can safely see, then think about what kind of snow it is. If it is deep, wet, or crusted with ice, and the roof is older or already shows warning signs, that is the time to act. Remember that drifts can pile snow several times deeper in one area, such as a valley or the lee side of a dormer, than on the rest of the roof.
Roof Rake or Shoveling? What Is Safe to Do Yourself
Roof snow removal injures people every winter, and the main danger is not the snow. It is the fall. A roof covered in snow or ice is among the most hazardous places a homeowner can stand, and shingles cover up how slippery it really is. The safest rule is simple: do not climb onto a snowy roof.
What you can safely do from the ground:
- Use a long handled roof rake on single story roofs. Pull snow down from the lowest three to four feet of the roof, working from the edge up. This reduces ice dam risk and takes weight off the most vulnerable part of the roof.
- Clear in layers instead of all at once. Take a little at a time. Pulling a large pile down at once puts weight in one spot and can send an avalanche of snow onto you.
- Do not scrape down to bare shingles. Leave a thin layer. Scraping can tear off the granules that protect the shingles and shorten the life of your roof.
- Avoid sharp tools and ice chippers. These damage shingles and flashing.
- Skip rock salt and calcium chloride. These are corrosive to gutters and metal and can damage shingles over time.
- Watch what is below you. Keep people, pets, vehicles, and walkways clear of the area where the snow will fall, and watch for power lines and service drops.
Our guide to New England winter roofing covers the six inch rule for clearing roof edges after a heavy, wet snowfall, along with a full winter maintenance checklist.
When to Hire a Professional
A roof rake works for the lower portion of a one story roof. It does not work for everything. Bring in a professional if any of the following apply:
- The home is two stories or more, or the roof is steep.
- The snow is heavy, wet, or turned to thick ice.
- You are seeing any of the warning signs listed above.
- Ice dams have formed and water is entering the house.
- Snow has built up on a section you cannot reach from the ground.
Professional crews use fall protection, proper tools, and a method that removes the load without damaging the roof. Ice dams are a separate job, since chipping at them with a hammer or axe damages shingles, and professionals use safer techniques such as low pressure steaming. If you want to know what that service involves, our roof shoveling and ice dam removal service explains how we remove snow and ice without harming the roof underneath.
A good crew will also be honest about how much to remove. The goal is not a bone dry roof. It is relieving excess weight and clearing the edges where ice dams form, and leaving the shingles intact.
How Snow Load Connects to Ice Dams and Leaks
Snow weight and ice dams are related but different problems, and homeowners often confuse them. Snow load is about structural weight. Ice dams are about water. They form when heat escaping from the house melts snow on the upper roof, the meltwater runs down to the cold edge, and it refreezes there. The growing ridge of ice blocks drainage and pushes water back up under the shingles, where it can leak into the ceiling and walls.
The two problems often arrive together. A roof with deep snow is also one that tends to develop ice dams, and the water can soak insulation and decking, which in turn weakens the roof. The fix is usually a combination of removing excess snow from the edges, improving attic insulation and ventilation so the roof stays cold, and sealing air leaks that let warm air into the attic. Preventing the melt cycle is far cheaper than repairing the damage it causes.
Metal Roofs and Snow
Metal roofs behave differently. Snow tends to slide off a smooth metal surface, which reduces long term weight buildup, but it can release suddenly in large sheets. That matters if the roof sits above a walkway, entry, deck, or shrubs. Snow guards break up the slide and let snow release in smaller amounts. If you are weighing materials, our metal roofing page explains the differences between the main panel systems and how they handle New Hampshire winters.
What to Do If You See Damage After a Heavy Storm
If you notice a leak, sagging, or damaged shingles after a storm, document it before anything is repaired. Take dated photos of the roof, ceilings, and any water stains, and note when the damage appeared. If the damage is clearly storm related, that record can matter for an insurance claim. Temporary protection, such as a tarp, may be needed to prevent further water damage while permanent repairs are arranged. Our storm damage repair page covers how we assess damage and handle emergency protection.
A Simple Winter Plan for NH Homeowners
You do not need to watch your roof anxiously all winter. A few habits cover most of the risk:
- Know your roof’s age and condition. Older homes and roofs with past repairs deserve more attention than newer ones.
- Get an inspection before winter. Catching loose flashing, damaged shingles, and ventilation problems in the fall is much cheaper than fixing leaks in January.
- Keep gutters and edges clear. Good drainage reduces ice buildup at the eaves.
- Check the weather forecast for rain after snow. Rain on snow is the combination that most increases weight, so it is the time to look at the roof carefully.
- Rake the edges after heavy, wet storms. Use a roof rake from the ground, and never climb up.
- Know the warning signs. Sounds, sticking doors, new cracks, sagging, and leaks are all reasons to call a professional promptly.
- Have a number to call. Line up a roofer before you need one, since crews get busy fast after a big storm.
Frequently Asked Questions
How much snow can a roof hold in New Hampshire?
It depends on the age of the home and how it was built. Newer homes are designed around the local ground snow load, which is about 70 pounds per square foot in towns like Bedford, Manchester, and Concord, and the roof design load is calculated from that figure. Older homes, especially those built between 1970 and 2000, may have been framed to a lower standard, so there is no single number that fits every roof.
How do I know if there is too much snow on my roof?
Weight matters more than depth. Watch for creaking or popping sounds from the roof or attic, doors and windows that suddenly stick, new cracks in ceilings or drywall, visible sagging, and new leaks. Heavy, wet, or rain soaked snow and snow turned to ice are the most concerning, since they weigh far more than fluffy powder.
Should I shovel snow off my roof myself?
For most homeowners the safe limit is using a long handled roof rake from the ground to clear the lowest few feet of a single story roof. Climbing onto a snowy or icy roof is dangerous and can also damage shingles. For two story homes, steep roofs, or heavy loads, hiring a professional with proper safety equipment is the safer choice.
Is it bad to leave snow on my roof?
Not always. A light layer of snow on a sound roof usually melts off without a problem. The concern is heavy accumulation, repeated thaw and freeze cycles that turn snow into dense ice, and snow building up along the eaves, which can cause ice dams and leaks.
Does rain on snow make my roof more dangerous?
Yes. Rain soaks into the snowpack and adds weight without reducing depth, so a roof can carry a much heavier load than it did before the rain. Rain on snow storms deserve extra attention, especially on older roofs.
Not Sure About Your Roof Before Winter? Get a Free Inspection
The right answer depends on the age of your roof, how it was framed, and what condition it is in, and that is something that has to be judged in person. Nick Tracey Roofing is based in Bedford and offers free, no obligation inspections across New Hampshire and Massachusetts, along with roof shoveling and ice dam removal through the winter. Contact us to schedule a visit before the snow flies.
