What snow load does a New Brunswick roof carry?

New Brunswick roofs must be designed to carry significant snow loads — the National Building Code of Canada (NBC) specifies ground snow loads ranging from roughly 1.5 kPa in parts of southern NB to over 3.0 kPa in northern regions like Edmundston and Campbellton, with the roof snow load calculated from that ground figure using slope and exposure factors.

To put that in practical terms, 1.0 kPa is roughly 100 kg per square metre. A northern NB roof carrying a 3.0 kPa ground snow load could see 200–250 kg per square metre on the roof surface once drift accumulation, ice, and wet spring snow are factored in. That is a serious structural demand, and it is why NB building code requires roof framing — rafters, trusses, ridge beams, and supporting walls — to be engineered for these regional loads rather than built to a generic national minimum.

The NBC uses specified snow load (Ss) values mapped by location. For NB, some representative ground snow load figures are approximately:

• Fredericton: ~2.0–2.2 kPa
• Moncton / Dieppe: ~1.8–2.0 kPa
• Saint John: ~1.5–1.8 kPa (lower due to coastal rain events that melt snow)
• Bathurst / Miramichi: ~2.2–2.5 kPa
• Edmundston / Campbellton: ~2.8–3.2 kPa
• Shediac / coastal Northumberland: ~1.8–2.2 kPa

Your actual permit drawings and structural engineer will reference the specific Ss value for your municipality or RSC jurisdiction — these are the numbers that govern your roof framing design.

Why This Matters for Renovations

If you are adding a dormer, converting an attic to living space, installing solar panels, or building an addition, the existing roof structure must be assessed against these loads before any work begins. An attic conversion adds dead load (insulation, flooring, drywall) on top of the existing snow load demand — what was adequate for storage may not be adequate for a bedroom. A structural engineer's assessment is not optional here; it is a building permit requirement.

Roof pitch plays a major role as well. Steeper roofs (6:12 pitch and above) shed snow more readily, reducing the accumulated load. Flat or low-slope roofs (under 3:12) accumulate snow and ice and must be designed with higher load capacity. If your NB home has a low-slope roof section — common on additions, garages, and some mid-century bungalows — that section deserves particular attention during any roofing project.

Ice Damming Compounds the Problem

NB's 100+ freeze-thaw cycles annually mean ice dams are a real structural and moisture threat, not just a cosmetic nuisance. Ice accumulation at the eaves adds concentrated load right where the roof structure is most vulnerable. Proper attic insulation (minimum R-50 in NB), continuous soffit-to-ridge ventilation, and a minimum 2-metre run of ice-and-water shield membrane at the eaves are code requirements during any NB roofing project — and they are your best defence against both ice dam formation and the water infiltration that follows.

When replacing a roof on your NB home, confirm your contractor is installing ice-and-water shield to the full code-required coverage, using architectural shingles rated for your regional wind and snow exposure, and that the decking underneath is sound. Wet, delaminated OSB sheathing is common under old NB roofs and must be replaced before new shingles go on.

If you are concerned about your existing roof's capacity to handle NB snow loads — particularly on an older home, a flat-roof section, or after a heavy snowfall season — a structural engineer's assessment runs roughly $500–$1,500 and is money well spent before a renovation or before you notice a problem.

Need help finding an experienced roofing or structural contractor in your area? New Brunswick Renovations can connect you with local professionals for free.