Roof Snow Load, Wind Speed and Ice Barrier Rules in Utah

Salt Lake City’s east bench can be built to carry four or five times the snow load required a few miles away on the valley floor, and that gap is exactly why Utah never printed one statewide number to begin with. The design figure that governs a permit here comes from a lookup at a specific street address, not from a map of the state. Before you or a builder orders trusses, run that address through the state’s ground snow load tool rather than borrowing a number from a neighbor’s house.

What is the ground snow load in Utah?

There isn’t one figure for Utah, and that absence is the actual answer. Under ASCE 7-16, the edition that IRC/IBC 2021 makes applicable in most states, the national snow map marks the entire state as a case-study region, meaning the map simply has no value to give here. Utah’s own state code responds to that gap by directing designers to the SEAU/USU ground snow load tool, which returns a load calculated for one street address rather than one city or county.

That address-specific number is what shows up on a permit application, gets checked in plan review, and drives the truss drawings a builder orders from the shop. It’s a ground figure, not a roof figure. The code applies exposure, thermal and slope factors to convert it before it ever becomes the load a rafter or truss is sized against, which is the subject of the next section.

To see how much that ground number can swing inside a single city, look at Salt Lake City itself. ASCE 7-22, the coming edition, maps the point at City Hall (40.7608, -111.8910, elevation 4,267 feet) at 38 psf on a strength-level basis, roughly 27 psf if you tried to compare it to the older nominal basis, though the two aren’t directly interchangeable since they use different load factors. Within Salt Lake City alone, that same 7-22 mapping runs from 33 psf on the valley floor up to 76-127 psf on the east bench. That is not a sign of a worsening climate between editions. It’s the reason the state abandoned a single city number in favor of an address lookup in the first place. The figure that actually governs your permit today is the ASCE 7-16 value the SEAU/USU tool returns for your address, not the 7-22 figure quoted above for illustration.

How much snow can a roof hold in Utah?

There’s no single number for this either, and anyone who gives you one is guessing. What can be worked out is how the ground figure at your address turns into a roof figure, and where that roof figure quietly gets worse.

From ground load to roof load

For an ordinary heated house with a sloped roof, the code typically lands the design roof snow load near 0.7 of the ground value, and lower still on a steep pitch that sheds snow on its own. That’s the baseline. It rises sharply wherever snow doesn’t stay put evenly: piled against a parapet or a taller adjoining wall, sliding off a steep upper roof onto a lower one, or building up below a dormer. Drift loading, not the flat-roof average, is where most snow-related roof failures actually start. Snow that drifts against a wall or collects in a valley can run several times the uniform design load in that one spot, even though the roof as a whole is nowhere near overloaded. The same mechanism turns a modest seasonal total into a structural emergency in other snow-heavy states, including Minnesota, where drift against parapets and rooftop equipment is a routine winter callout.

Depth is not weight

A foot of snow in January is not the same load as a foot of snow in March, because weight depends on what the snow has become, not how deep it is. Fresh, light powder runs roughly 5 to 7 pounds per square foot for every foot of depth. Settled or wet snow can run two to three times that, and a layer that has partly melted and refrozen into ice weighs more again. A roof that shrugged off two feet of dry January powder can be under real stress from ten inches of wet March snow sitting on top of an ice layer.

Watch for interior doors that suddenly stick or stop closing, new cracks spreading across ceiling drywall, or a ridge line that looks like it’s sagging when you view the roof from the street. Any of those is a reason to call your building department or a licensed engineer, not to climb up and check for yourself. If a roof needs relief, the safe move is raking snow off from the ground with a roof rake, working from the eaves inward. Getting on a loaded roof to shovel it is how people get hurt, and it doesn’t tell you anything a ground-level look and a phone call can’t.

What wind speed must a roof withstand in Utah?

At Salt Lake City, the basic design wind speed under ASCE 7-16 is 103 mph, for Risk Category II buildings, which covers ordinary single-family houses. ASCE 7-22 maps the same point at the same 103 mph, so this is one of the rare cases where the coming edition doesn’t move the number. That figure is a 3-second gust measured at 33 feet in open, flat terrain classified as Exposure C. It is not a sustained wind, not a hurricane’s headline sustained speed, and not what a weather forecast means when it reports “wind speed” for the day. Comparing it directly to a hurricane category number will make the code look weaker than it is. The two describe different things.

Utah’s inland location keeps this discussion focused on thunderstorm downdrafts and canyon or downslope wind events rather than the hurricane-driven windborne debris regions that some coastal codes map, and nothing in the state’s wind figures points to a debris-impact requirement here the way it does along a hurricane coastline.

What the 103 mph figure actually buys on a house is less dramatic than the number suggests, but it’s what a builder and an inspector check against: the wind rating printed on a bundle of shingles, the nailing pattern used to install them, how the roof sheathing is fastened to the framing, and the hardware, such as hurricane clips or straps, that ties the roof structure down to the walls below it. Edges, rakes and ridges fail first in high wind, because that’s where uplift pressure concentrates, which is why code nailing patterns tighten up specifically in those zones rather than staying uniform across the whole roof plane.

Does Utah require an ice barrier under the shingles?

An ice barrier is a self-adhering waterproof membrane installed under the shingles, running up from the eave edge and past the point where the interior wall line sits below the roof. Its job isn’t to keep snow off the roof at all. It’s there to stop meltwater that has backed up behind an ice dam from finding a seam and reaching the roof deck underneath.

Where the risk actually comes from

Ice dams form from heat, not weather. Warm air leaking from the living space into the attic melts the underside of the snow layer on the roof. That meltwater runs down until it reaches the cold overhang past the exterior wall, where there’s no warm attic below to keep it from refreezing, and it dams up there, forcing water back under the shingles above it. At Salt Lake City, NOAA’s 1991-2020 climate normals put the coldest month’s average daily minimum at 24.2°F, which is comfortably cold enough, combined with the region’s snow loads, for that freeze-thaw cycle to run repeatedly over a winter in an attic that isn’t well sealed and insulated.

Utah’s own residential rules are set out in the Utah State Construction Code, based on the 2021 International Residential Code, administered by the Uniform Building Code Commission and the Division of Professional Licensing, and it is a uniform code that cities and counties may not weaken. The model 2021 IRC ties its ice-barrier membrane requirement to areas with a documented history of ice forming along the eaves and causing water backup, a designation made at the local level rather than as one blanket statewide line. Because Utah’s published amendments to the code deal with basement egress and ceiling height rather than this provision, the underlying eave-protection requirement rides on how your jurisdiction has designated that risk. Confirm the specific requirement for your address with your local building department before a re-roof, the same way a homeowner further along a cold, snowy corridor would check the equivalent detail in a state like New York.

The membrane only ever treats the symptom. It protects the deck from water that has already backed up, but it does nothing to stop the dam from forming in the first place. Air sealing the attic floor and bringing insulation up to a proper depth are what actually keep the attic cold enough that snow on the roof doesn’t melt unevenly. A roof with a correctly installed ice barrier and a leaky, under-insulated attic above it will still ice-dam every winter. The membrane just buys time before the water finds its way in.

What roofing material suits Utah best?

The honest answer depends on which of Utah’s numbers matters most for your roofing project: the snow load at your specific address, the 103 mph basic wind speed at Salt Lake City, or the climate zone that governs how much insulation belongs under the deck. Utah spans three IECC climate zones, with 21 of its 29 counties in zone 5B, 7 in zone 6B, and 1 in zone 3B, so the insulation targets that pair with roofing choice differ across the state and are worth checking against the county table before you spec anything.

Architectural asphalt shingles are rated for wind resistance the way any product category is, and that rating only holds if the nailing pattern actually matches what the rating assumes. A high-wind-rated shingle fastened to a lower standard performs like the lower standard, not the rating on the wrapper. Standing-seam metal sheds snow cleanly and fast once it warms even slightly, which is an advantage for the roof structure but a hazard for whatever sits below the eave. Where snow will slide, that has to be planned for so it doesn’t land on a walkway, a doorway, or a driveway. Slate and concrete tile carry real dead weight of their own, and that weight adds directly to whatever snow load the roof structure has to carry on top of it, which matters more in a state where some addresses already carry a heavy site-specific ground snow figure.

Whichever material you’re weighing, the underlayment and fastening detail is doing as much work as the surface material itself wherever wind is the governing load. A premium shingle over a substandard nailing job or a poorly lapped underlayment gives you the failure mode of the cheaper system, not the one printed on the product label.