Rain landing on packed snow adds weight that lingers long after the storm ends, and that’s the part of snow-load talk most guides skip. New Brunswick’s design snow figures add a rain-on-snow component on top of the snow itself, and in this province that add-on is large enough to change how a roof gets framed. Ask your municipal or regional service commission building department, or a licensed engineer, for the specified roof snow load used on your permit, since that figure is calculated from several factors, not read off a map.
What is the ground snow load in New Brunswick?
At Moncton, the reference city the National Building Code of Canada 2020 lists for this part of the province, the ground snow load is Ss = 3.0 kPa, with an added rain load of Sr = 0.6 kPa, both set out in Appendix C, Table C-2 of the code. That pair of numbers describes the ground, not the roof. It is the starting point the code works from before anyone talks about rafters or trusses.
Ground load versus roof load
The code turns that ground figure into a roof figure with a formula: S = Is[Ss(Cb·Cw·Cs·Ca) + Sr]. The basic factor, the exposure factor, the slope factor and the accumulation factor all move the ground value up or down depending on the actual roof, and the rain term gets added back in at the end. Nobody hands a builder “3.0 kPa” and calls it done. What ends up on a truss drawing or a plan-review stamp is the output of that whole calculation, and it is the figure a building department or an engineer checks against, not the mapped ground value.
New Brunswick applies this through the National Building Code of Canada as adopted by New Brunswick Regulation 2021-2 under the Building Code Administration Act, based on the 2020 national edition. It is a uniform provincial code administered by the Department of Justice and Public Safety’s Technical Inspection Services, and it becomes mandatory for permits issued after March 31, 2025. Local or regional service commissions issue the permits and do the inspections, but the numbers in Table C-2 are provincial, drawn from the national code the province has adopted.
Moncton sits at roughly 20 metres elevation, and that is the site the 3.0 kPa and 0.6 kPa figures belong to. Higher ground and different microclimates elsewhere in the province carry different mapped values, which is exactly why Table C-2 lists individual localities instead of one number for the whole province. Prince Edward Island, just across the Northumberland Strait, works through a comparable rain-on-snow calculation of its own, covered in our guide to Prince Edward Island’s roof snow load and wind rules. For a project outside Moncton, the reference figure to ask for is the one your own service commission uses, not the one printed here.
How much snow can a roof hold in New Brunswick?
There’s no single number for this, and anyone who gives you one without asking about your roof’s shape and slope is guessing. What the code actually produces is a design load specific to a given roof geometry, and what the snow itself weighs changes as the winter goes on.
Where drift changes the math
Starting from Moncton’s ground figure, the code’s basic factor typically pulls an ordinary heated house roof with a normal slope down toward something in the neighborhood of seven-tenths of the ground value. Drift works the opposite way, and it is where roofs actually get overloaded: against a taller wall, below a dormer, into a valley between two roof planes, or on a lower roof sitting beside a taller one, the accumulation factor can push the local load well above the ground figure rather than below it. A roof that looks fine averaged across its whole area can still be carrying a dangerous pile in one corner.
The snow itself isn’t a fixed weight either. Fresh, light snow runs roughly 5 to 7 lb per square foot for each foot of depth. Once it settles, or takes on rain, that same depth of snow can weigh two to three times as much, and an ice layer on top adds still more. A foot of snow that fell in a cold January is not the same load as a foot sitting on the roof in March after a few freeze-thaw cycles have packed and wetted it. Wisconsin roofs face the same arithmetic through a different set of code numbers, covered in our page on Wisconsin’s roof snow load and wind rules.
Watch for signs the load is becoming a real problem rather than a cosmetic one:
- Interior doors that suddenly stop closing properly
- New cracks appearing in ceiling drywall, especially near the middle of a room
- A ridge line that looks like it’s sagging when viewed from the street
If you see any of that, the safe response is raking snow off from the ground with a roof rake, working from the eaves upward. Getting up onto a roof that’s already carrying a heavy, possibly icy load is not a safe way to find out how much more it can take. For anything beyond routine raking, that’s a building department or engineer question, not a guess based on how the roof looks from the driveway.
What wind speed must a roof withstand in New Brunswick?
Moncton’s reference hourly wind pressure, from NBC 2020 Table C-2, is q = 0.5 kPa for a 1-in-50-year return period, which is the value NBC Part 4 and Part 9 use for structural design. That is a pressure, not a gust speed. Canadian code figures and American mph gust ratings are built on different bases entirely, so there’s no honest way to convert one into the other or line them up side by side.
What the pressure figure controls
This number drives the practical decisions on a roof assembly: the fastening pattern for the sheathing, the wind rating chosen for the shingles or other covering, and the uplift connectors tying the roof structure down to the walls below. Edges, rakes and ridges are where uplift concentrates, which is why they’re usually the first place a roof covering or its fasteners fail in a bad windstorm, long before the field of the roof shows any distress.
The same Table C-2 line for Moncton also lists a 1-in-10-year hourly wind pressure of 0.39 kPa. That smaller figure is for serviceability checks, things like cladding deflection and comfort, and it is not the number used for strength design. Mixing the two up understates what the structural connections actually need to resist.
Both figures belong to Moncton specifically. More exposed stretches of New Brunswick’s coastline, particularly around the Bay of Fundy, can see different wind conditions than an inland reference station reflects, and Table C-2 lists separate localities precisely because a province-wide average would hide that. If you’re outside Moncton, ask your building department which reference figure applies to your site before assuming this one carries over directly.
Does New Brunswick require an ice barrier under the shingles?
An ice barrier is a self-adhering membrane installed at the eaves and run up past the interior wall line, and its job isn’t stopping snow. It’s stopping meltwater that backs up behind an ice dam from working its way under the shingles and into the roof deck.
What actually causes an ice dam
Heat escaping from the living space into the attic warms the underside of the roof deck over the heated part of the house. Snow sitting on that warm section melts, runs down the slope, and hits the roof edge overhanging the cold eave, where there’s no heat loss underneath to keep it liquid. It refreezes there, and layer by layer that ice builds a dam that backs meltwater up under the shingles above it. The membrane protects the deck from that backed-up water. It does nothing to stop the dam from forming in the first place. Only air sealing the attic floor and getting the insulation up to where it needs to be actually prevents the melt-refreeze cycle that builds the dam. A roof with a membrane and a leaky, under-insulated attic has bought protection against the symptom, not the cause.
Whether that cycle is a real risk here comes down to how cold it gets and how much snow sits on the roof to melt. Moncton’s mean daily minimum for the coldest month runs about -13.9°C, according to Environment and Climate Change Canada’s 1981-2010 climate normals, and that’s cold enough, paired with a substantial ground snow load, that the melt-and-refreeze conditions behind ice damming show up as a recurring winter pattern here rather than a rare event.
New Brunswick’s own code on this is the National Building Code of Canada as adopted by New Brunswick Regulation 2021-2 under the Building Code Administration Act, based on the 2020 national edition, administered by the Department of Justice and Public Safety’s Technical Inspection Services and mandatory for permits issued after March 31, 2025. The province hasn’t amended the model code’s eave-protection detailing, but exactly how far a membrane needs to run past the interior wall line depends on the roof slope and the local snow load figures the code assigns to your area. Confirm the current detailing for your project with your regional service commission before a re-roof, since it’s a permit-administered requirement even though the rule itself is set provincially.
What roofing material suits New Brunswick best?
Moncton’s combination of a 3.0 kPa ground snow load, a 0.6 kPa rain-on-snow addition, a 0.5 kPa design wind pressure, and a climate zone (NRCan zone 6, based on roughly 4,696 heating degree days at the Moncton A station) that keeps snow sitting on roofs for months, together shape which roofing category makes sense here. Once those figures are in hand, the next decision is roofing material.
Architectural asphalt shingles carry a published wind rating, but that rating only means something if the fastening pattern underneath matches it. A shingle rated for high wind, nailed to a lower standard, performs like the lower standard, full stop. Standing-seam metal sheds snow well once the roof surface warms, which is an advantage for keeping load off the structure, but that same slab of snow has to land somewhere. Positioning it so it doesn’t come down on a doorway, a walkway or a driveway is a design decision made at the time the roof is laid out, not something to discover the first time it happens. Slate and concrete tile add their own dead weight directly onto the structure, on top of whatever snow load the roof is already carrying, which is a real structural consideration in a design this heavy on rain-on-snow load.
Matching material to the loads
| Material | Wind behavior | Snow behavior | Added dead weight |
|---|---|---|---|
| Architectural asphalt shingles | Wind rating varies by product, fastening pattern decides real performance | Holds snow rather than shedding it | Light, adds little on top of the snow load |
| Standing-seam metal | Interlocking seams resist uplift when properly fastened | Sheds accumulated snow in slabs once the roof warms | Light, similar to shingles |
| Slate or concrete tile | Heavy units resist uplift by mass, but edge attachment still matters | Holds snow like shingles, little shedding | Substantial: tile weight adds directly to the load carried by the structure |
Whatever material a roof carries, the fastening schedule and the underlayment behind it decide how that material actually performs against Moncton’s wind pressure and rain-on-snow figures. A material choice made without matching those installation details to the local design values is a decision made on half the information.