Winnipeg’s ground snow load is set at 1.9 kPa, with another 0.2 kPa added for rain that falls on top of standing snow. That combined figure is the starting point an engineer or truss supplier works from, not the number that ends up stamped on your roof. Before assuming anything about your own house, pull your municipal building permit file or ask a licensed engineer which reduction and drift factors were applied to get from that ground figure to the load your rafters actually carry.
What is the ground snow load in Manitoba?
At Winnipeg, the National Building Code of Canada sets the ground snow load, Ss, at 1.9 kPa, with an associated rain load, Sr, of 0.2 kPa added on top (National Building Code of Canada, 2020 edition, Appendix C, Table C-2, elevation 235 m). Both numbers matter. The rain component exists because Canadian codes assume rain can fall onto standing snow and soak into it before it drains, adding weight the snow alone would not carry on its own.
Ground load versus roof load
This is a ground measurement, not a roof measurement, and the two are not the same thing. The code converts the ground figure into a specified roof snow load through the formula S = Is[Ss(Cb·Cw·Cs·Ca) + Sr], where a basic factor reduces the ground value for an ordinary roof and separate factors adjust it up or down again for exposure, roof slope and snow accumulation. Nobody’s rafters ever carry the raw 1.9 kPa ground figure: what they carry is that number after every one of those factors has been applied, and the arithmetic is done by whoever draws the truss package, not by the homeowner.
That converted figure is what shows up on a building permit application and on the truss drawings a supplier stamps before fabrication. A plan reviewer at the municipal building department checks it against the Manitoba Building Code, Manitoba Regulation 78/2023, Manitoba’s own uniform provincial code, derived from the National Building Code of Canada’s 2020 edition and administered by the Office of the Fire Commissioner’s Building Codes Section. It has been in force since January 1, 2024.
Table C-2 lists Winnipeg as one reference locality among many across the country, and other Manitoba communities carry their own listed values that can run higher or lower depending on elevation and local climate. None of this settles whether a particular roof is adequate. That answer belongs to the municipal building department reviewing the permit, or to a licensed engineer looking at the actual structure, not to a number pulled off a reference table.
How much snow can a roof hold in Manitoba?
There is no single figure that answers this, and anyone who gives you one is guessing. What the Manitoba Building Code actually specifies is a converted roof snow load worked out from Winnipeg’s 1.9 kPa ground figure and 0.2 kPa rain component, and that converted number changes with the roof itself.
For an ordinary heated house roof with a normal slope, the code’s basic factor lands the design load somewhere near seven-tenths of the ground value, a genuine reduction from the raw 1.9 kPa figure. A steep roof gets a further reduction, since steep slopes shed snow instead of holding it. A roof with a low slope, or one that traps snow against a wall or under a dormer, gets the opposite treatment, because the code’s accumulation factor pushes the design load up in exactly those spots, sometimes well above the ground figure itself.
Where drift does the damage
Drift is where roofs actually fail, and it rarely happens where anyone is looking. A lower roof next to a taller wall collects snow sliding off the wall above it. A valley between two roof sections collects snow from both sides. The area below a dormer or a rooftop mechanical unit collects snow the wind has scoured off the open field of the roof. Each of these spots can be carrying several times the load of the open roof beside it, on the same building, under the same storm. Saskatchewan’s flat, wind-exposed prairie produces the same drift problem for the same reason, worked out from its own Table C-2 figures in our guide to Saskatchewan’s roof snow load and wind rules.
The depth of snow on a roof tells you almost nothing on its own. Fresh, dry powder is far lighter per unit of depth than snow that has settled, and settled snow is lighter again than snow that has partly melted and refrozen into an ice layer. A roof that shed a foot of January powder without complaint can be in real trouble under a foot of wet March snow sitting on top of an ice lens, because the second foot weighs several times what the first one did.
Watch for practical warning signs instead of trying to estimate weight:
- Interior doors that suddenly stick or won’t latch
- New cracks running across ceiling drywall
- A ridge line that looks like it’s bowing when you sight along it from the yard
Any of these is a reason to act, and the safe response is raking snow off from the ground with a roof rake, working from the eave inward, never climbing onto a loaded roof to shovel it by hand.
What wind speed must a roof withstand in Manitoba?
At Winnipeg, the National Building Code of Canada sets the reference hourly wind pressure at 0.45 kPa for a 1-in-50-year return period, and that is the figure the Manitoba Building Code uses for structural design under both Part 4 and Part 9 (National Building Code of Canada, 2020 edition, Appendix C, Table C-2). This is a pressure measured over an hour on open terrain, not a three-second gust and not the number a weather forecast calls wind speed, and it is worked out on a different basis than American gust speeds entirely. The two figures are not comparable, and converting one into the other would produce a number neither code actually recognizes.
What the pressure governs on the roof
A second figure appears alongside it: 0.36 kPa at the 1-in-10-year return period. That lower figure covers serviceability only, things like how far a wall assembly is allowed to deflect or how much cladding is expected to flex in an ordinary storm. The 1-in-50-year figure of 0.45 kPa, not the 1-in-10-year one, is what governs structural strength, including the connections that keep a roof frame attached to the walls beneath it during the strongest wind Winnipeg sees across a typical fifty-year span.
That pressure translates into several concrete requirements once it reaches an actual roof: the wind rating printed on a bundle of shingles, the nailing pattern a roofer is supposed to follow rather than whichever one is fastest, the fastening schedule for the sheathing panels under the shingles, and the uplift connections, straps or clips, tying the roof frame down to the wall frame. Edges, rakes and ridges are where those connections matter most, because wind flowing over a roof concentrates its uplift force right at those transitions rather than across the open field of the roof, where most of the surface area sits but where the least force actually pulls upward.
Winnipeg’s figure comes from a single reference station, and Table C-2 lists other Manitoba localities with their own values, some higher, particularly in more exposed parts of the province. Coastal British Columbia works from an entirely different set of wind and snow figures again, a comparison covered in our guide to British Columbia’s roof snow load and wind rules. Whether a given roof’s fastening actually meets the design pressure for its site is a question for the municipal building department reviewing the permit, or for a structural engineer inspecting the connections directly, never something to estimate from a reference table alone.
Does Manitoba require an ice barrier under the shingles?
An ice barrier is a self-adhering waterproof membrane installed directly on the roof deck, run up from the eave edge past the point where the wall below is heated, usually far enough to clear the interior wall line by a margin. Its job has nothing to do with stopping snow from accumulating. It exists to stop meltwater from an ice dam from working backward under the shingles and into the roof deck once normal shingle lap and gravity stop being enough to keep it out.
Winnipeg’s coldest month runs to a mean daily minimum of about -21.4°C (Environment and Climate Change Canada’s 1981-2010 climate normals for Winnipeg), and that kind of cold, combined with a ground snow load of 1.9 kPa plus 0.2 kPa of rain load sitting on roofs through the winter, is exactly the combination that produces ice dams.
What causes an ice dam
An ice dam forms when heat escaping through the attic melts the underside of the snow layer on a warm roof section, that meltwater runs down to the cold eave overhanging the unheated exterior, and refreezes there, building a ridge of ice that backs water up under the shingles above it. That mechanism is also why the membrane is only half the fix. It protects the roof deck from water that has already found its way past the shingles; it does nothing to stop the ice dam from forming in the first place. Only sealing the air leaks between the living space and the attic, and making sure the attic has enough insulation for the local climate, stops the dam from building.
Winnipeg sits in climate zone 7a under Natural Resources Canada’s zoning system, based on roughly 5,648 heating degree days a year measured at Winnipeg Richardson International Airport, a demanding zone for attic insulation levels and one where marginal air sealing shows up fast as ice damming along the eaves.
The Manitoba Building Code, Manitoba Regulation 78/2023, is Manitoba’s own uniform provincial code, derived from the National Building Code of Canada’s 2020 edition and in force since January 1, 2024, administered by the Office of the Fire Commissioner’s Building Codes Section. Confirming the exact eave protection requirement that applies to a specific roof, including how far up the roof plane the membrane has to run, is a question for that office or for the municipal building department handling the permit, not something to assume from a general description of how ice dams work.
What roofing material suits Manitoba best?
The honest answer starts from Winnipeg’s own numbers: a ground snow load of 1.9 kPa plus 0.2 kPa of rain load, an hourly wind pressure of 0.45 kPa at the 1-in-50-year return period, and a climate zone of 7a under Natural Resources Canada’s system. Those three figures together, not any single one of them, decide what a roofing material actually has to do here. Before comparing materials, it helps to have the structural side of the job settled first, which is what our broader guide to Roofing works through.
Comparing the categories
Asphalt shingles hold snow on the roof rather than shedding it, which spreads the load out but also means the roof is carrying that weight for longer through the winter. Standing-seam metal releases accumulated snow in a sudden slide once a warm spell or direct sun loosens it from the panel, which is efficient for the roof structure but means whatever sits below that eave, a doorway, a walkway, a parked vehicle, needs to be somewhere the slide is expected and designed for, not somewhere it happens to land. Slate and concrete tile carry their own dead weight in addition to whatever snow sits on top of them, so that dead weight has to be accounted for separately from the design snow load, not folded into it as an afterthought.
| Roofing type | Snow behavior | Wind consideration | Added weight |
|---|---|---|---|
| Asphalt shingles | Holds snow in place, sheds gradually as it melts | Wind rating is only as good as the nailing pattern actually used | Light, adds little on top of the design snow load |
| Standing-seam metal | Sheds accumulated snow in a sudden slide | Panel and clip fastening carries the uplift, not the finish | Light, similar to shingles |
| Slate or concrete tile | Holds snow much like shingles | Extra mass resists uplift somewhat on its own | Its own dead weight adds to the design snow load |
Where wind governs the design, the fastening and the underlayment matter more than which material sits on top. A high wind-rated shingle nailed with the wrong pattern, or spaced too far apart, performs to the standard of that nailing, not to the rating printed on its wrapper. The same is true of standing-seam panels: the clip spacing and fastener type carry the uplift load the code specifies, and a panel profile chosen for its look rather than its fastening system does not automatically meet Winnipeg’s 0.45 kPa wind pressure just because it is metal.
None of this settles which material is right for a particular house. That still depends on the roof’s actual slope, its exposure, and what a structural review of the specific building says, a conversation for a contractor working from stamped drawings or for the municipal building department reviewing the permit, not a conclusion to draw from a general comparison table.