Cheyenne’s mapped ground snow load is 20 psf, but that figure never reaches a rafter unchanged. Once slope, exposure and heat loss are factored in, an ordinary heated roof at that same location works out closer to 14 psf. Pull the design snow load and basic wind speed your local building department actually used on the permit, because Wyoming leaves adoption of the residential code to each city and county rather than setting one figure statewide.
What is the ground snow load in Wyoming?
The ground snow load mapped for Cheyenne, Wyoming is 20 psf under ASCE 7-16, the edition of the design standard that IRC/IBC 2021 makes applicable in most states. That number describes the load sitting on open, level ground on a winter design day. It is not the load a roof deck actually carries. The code applies exposure, thermal and slope factors before the figure ever reaches a truss drawing, and for an ordinary heated sloped house roof at Cheyenne the result works out to roughly 14 psf of roof snow load.
This converted figure is the number a permit application, a plan reviewer and a truss manufacturer actually use. When a builder orders roof trusses, the snow load line on that engineering package traces back to this map, not to the raw ground figure. A steeper roof, a colder unheated outbuilding, or a roof sheltered by taller terrain each pull that 0.7 baseline up or down.
ASCE 7-22, the edition a handful of jurisdictions are beginning to look at, maps the same Cheyenne point at 46 psf. That is not three times the snow. The 7-22 figure is a strength-level value meant to be used with a 1.0 load factor, while the 7-16 figure above is nominal, meant to be used with 1.6. The gap between the two numbers reflects that change in basis, not a worsening winter and not a sign that a roof built to the current figure is undersized.
Cheyenne sits at roughly 6,084 feet, and snow load climbs and falls with elevation across Wyoming. A mountain valley or a ridge community can carry a design figure far removed from this one. Wyoming has no statewide residential building code, so the exact load used on a given permit is decided by the city or county issuing it, not by a single state agency. Confirm the design figures with the local building department before assuming Cheyenne’s numbers apply anywhere else in the state.
How much snow can a roof hold in Wyoming?
There is no single number for this, because the answer depends on what the snow has become and where it has piled up, not just how many inches fell. Start from the same Cheyenne figure discussed above. An ordinary heated sloped roof there is designed for roughly 14 psf, derived from the 20 psf ASCE 7-16 ground snow load once exposure, thermal and slope factors are applied. A steep roof sheds load faster and can carry a lower design figure. A low-slope roof holds snow longer and carries close to the full converted value.
Drift is where the real risk sits, not the flat field the ground map describes. Snow driven by wind piles against a parapet, below a dormer, against a taller adjoining wall, or onto a lower roof beside a taller one. A drift can load that one section of roof to several times the field value the rest of the roof carries. That is a local condition, not an average one, and it is why two roofs of identical size and slope in the same town can end up carrying very different actual loads.
Why depth alone does not tell you the load
A foot of fresh, dry powder weighs far less than a foot of wet spring snow sitting on top of an older pack. Fresh light snow runs roughly 5 to 7 pounds per square foot per foot of depth. Snow that has settled, partly melted and refrozen, or arrived wet, runs two to three times that. A layer of ice on top of a compacted pack adds more still, pound for pound, than an equivalent depth of anything else on the roof. A foot of January powder and a foot of March slush are not the same load, even though a tape measure says otherwise.
Watch the building, not the sky. Interior doors that begin sticking or won’t latch, new cracks opening in ceiling drywall, and a ridge line that starts to look wavy or sagging from the ground are signs a roof is carrying more than it was built for. Raking snow from the ground with a roof rake is the safe response; climbing onto a loaded roof to shovel it is how people get hurt, both from the fall and from the roof itself giving way underfoot. In places where the mapped ground snow load runs many times higher than Cheyenne’s, such as Newfoundland and Labrador, drift-driven local overload is a routine design concern rather than an edge case, and the same watch-the-building logic applies there too.
None of this tells you whether a specific roof is adequate. That determination belongs to whoever designed it, or to a licensed engineer reviewing it now, working from the actual design documents and the actual load on the day in question.
What wind speed must a roof withstand in Wyoming?
The basic design wind speed mapped for Cheyenne, Wyoming is 108 mph under ASCE 7-16, for Risk Category II buildings, which covers ordinary houses. That is a 3-second gust measured at 33 feet above ground in open, Exposure C terrain, not a sustained wind and not the sort of figure a weather forecast reports. A forecaster’s sustained wind speed is averaged over a longer interval, and comparing it directly to the code’s gust figure makes the code look far weaker than it actually is. They are not the same measurement.
ASCE 7-22 maps the same Cheyenne location at the same 108 mph. Where the two editions agree this closely, the coming edition changes little about what a roof needs to resist here, unlike the snow load figure discussed above.
Wyoming’s Cheyenne figure carries no wind-borne debris flag. That designation, where it applies, requires impact-rated glazing or approved shutters on new construction, a real obligation tied to hurricane-prone coastlines. It does not apply at this inland location. A reader comparing notes with someone building on a hurricane coast, where a page like the Connecticut snow and wind load rules lays out a coastal debris region alongside its own design wind speed, is looking at a different set of obligations entirely.
What the number actually governs
The 108 mph figure sets the shingle wind rating a roofer specifies, the nailing pattern used to fasten each course, how the sheathing itself is fastened to the rafters, and the uplift connections, straps and clips, tying the roof structure down to the wall framing below. Edges, rakes and ridges fail first in a wind event, because that is where uplift pressure concentrates, which is why code nailing patterns tighten up specifically along those lines rather than applying one spacing across the whole field of the roof.
Exposure category matters too. A house sheltered by trees or terrain, Exposure B, sees lower effective pressures than the same 108 mph figure applied in open range country, Exposure C, and the building department assigns that category at permit review, not the homeowner. None of this tells an individual reader whether their existing roof, windows or tie-downs meet the current standard. That determination belongs to the local building department, or to a licensed contractor or engineer working from the actual permit history of the structure.
Does Wyoming require an ice barrier under the shingles?
An ice barrier is a self-adhering waterproof membrane installed on the roof deck at the eaves, running up from the edge past the interior line of the exterior wall. It is not there to keep snow out. Its job is to stop meltwater that has backed up behind an ice dam from finding a seam in the shingles and reaching the wood deck underneath.
What actually causes an ice dam
An ice dam forms when heat escaping from the living space into the attic warms the underside of the roof deck enough to melt the snow sitting on it, even while the outside air stays well below freezing. That meltwater runs down the slope until it reaches the eave, which stays cold because it overhangs unheated space, and refreezes there into a ridge of ice. Water backing up behind that ridge is what an ice barrier is built to stop. The membrane treats where the water ends up, not why it appeared in the first place: only attic air sealing and adequate insulation stop the dam from forming at all. A roof with a membrane and a poorly insulated attic still grows ice dams every winter. It just doesn’t leak while it does.
Cheyenne’s coldest-month mean daily minimum runs 18.1°F under NOAA’s 1991-2020 climate normals, cold enough that snow sitting on a roof stays put for extended stretches rather than melting off between storms. Combined with a design roof snow load built around the 20 psf ground figure discussed above, the conditions for repeated freeze-thaw cycling at the eaves are present in an ordinary Cheyenne winter, and colder, higher-elevation parts of the state see this more, not less.
Wyoming has no statewide residential building code, and no state agency administers one for houses. The edition in force, and any amendment to it, including whether an ice barrier is required and how far up the roof it must run, is decided by whichever city or county issues the building permit. There is no single statewide answer to give here. Check with the building department for the jurisdiction where the roof sits, since that office can name the exact code edition in force and the ice barrier requirement it carries, if any.
What roofing material suits Wyoming best?
The honest answer comes from stacking the local numbers together: a 20 psf ground snow load at Cheyenne under ASCE 7-16, a 108 mph basic design wind speed at the same location, and the 2021 IECC’s climate zone map, which puts 17 of this state’s 23 counties in zone 6B, 3 in zone 7 and 3 in zone 5B. Cold and dry across most of the state, colder still at higher elevation counties, and a wind figure that governs fastening more than it governs material choice. That combination should drive a material decision, not a general reputation one material has over another.
Architectural asphalt shingles
Asphalt shingles carry a published wind rating from the manufacturer, and that rating only holds if the shingle is installed with the nailing pattern and fastener count it was tested with. A shingle rated for high wind and nailed to a lower standard performs to the lower standard, not the one printed on the wrapper. On snow load, asphalt shingles hold snow in place rather than shedding it quickly, which keeps the load spread across the roof rather than dumping it in one place below the eave.
Standing-seam metal
Metal roofing sheds snow well once it starts sliding, an advantage for load, since less snow sits on the roof at any one time, and a hazard for anything below the eave. Where a metal roof is chosen, the eave it sheds toward, over a doorway, a walkway or a driveway, is a design decision that has to be made on purpose, not discovered the first time a slab of snow comes off unannounced.
Slate and concrete tile
Slate and concrete tile add their own dead weight to whatever snow load the structure has to carry, on top of, not instead of, the design snow load discussed above. A structure has to be engineered for that combined weight from the start. Retrofitting a lighter roof to carry tile after the fact is a structural question for an engineer, not a roofing decision.
| Material | What governs it here | Where the load goes |
|---|---|---|
| Architectural asphalt shingles | Manufacturer wind rating, tied to the fastening pattern actually used | Holds snow in place on the roof plane |
| Standing-seam metal | Panel and seam wind uplift resistance | Sheds snow off the eave in slabs |
| Slate and concrete tile | Structure sized for the tile’s own dead weight plus snow load | Adds permanent weight the frame carries year-round |
Whatever the choice, the fastening and the underlayment beneath it matter as much as the material itself where wind governs the design. The general basics that apply to any material, deck condition, correct fastening, the right exposure category, are covered in broader terms under roofing. None of this substitutes for a design done by whoever is signing off on the permit for the specific structure in question.