Anchorage’s design ground snow load is 50 pounds per square foot, and that single number is what decides everything else on this page: the truss span an engineer specs, the wind uplift connections a builder orders, whether an ice barrier goes under the shingles. It sits on the ground, not the roof, and the code trims it down before it ever reaches a rafter. Check with your municipal building department before assuming a converted figure like this applies to your own address.
What is the ground snow load in Alaska?
The design ground snow load for Anchorage is 50 pounds per square foot under ASCE 7-16, the edition referenced by the 2021 IRC and IBC in most states and mapped at 61.2181, -149.9003 at an elevation of 500 feet. That is the figure a permit application, a plan review and a set of truss drawings actually use when a house is designed or a roof is replaced in that city.
From the ground to the rafter
It is a ground figure, not a roof figure, and that distinction matters more than any other on this page. Snow behaves differently on open ground than it does on a sloped, heated house roof, so the code applies exposure, thermal and slope factors before the number reaches a rafter. For an ordinary heated sloped roof, that conversion lands the roof snow load at roughly 35 pounds per square foot, and a steeper roof brings the working number down further because snow slides off before it can build up.
Why the newer edition isn’t the answer
A newer edition, ASCE 7-22, maps the same Anchorage point at 80 psf. That is not more snow falling on the same city, and it is not a sign that a house built to the earlier figure is now undersized. The two numbers sit on different bases. ASCE 7-16 is a nominal value used with a 1.6 load factor, while ASCE 7-22 is a strength-level value used with a 1.0 load factor, so the gap between them reflects arithmetic, not weather. A few jurisdictions are beginning to adopt 7-22, but the 50 psf ground figure and the roughly 35 psf roof figure from 7-16 remain what a permit in most of the state uses right now.
Both figures belong to Anchorage specifically. Ground snow load shifts by a large margin with elevation inside a single state, and a reading from a valley floor tells you nothing reliable about a ridge a few miles away. Anyone designing or repairing a roof outside Anchorage should ask their municipal building department which figure applies at their site rather than borrow this one.
How much snow can a roof hold in Alaska?
There is no single number for this, because a roof’s actual snow load depends on more than the ground figure. It depends on slope, on how wind has moved snow around the roof, and on what the snow has turned into after weeks of freeze and thaw. Anchorage’s roughly 35 psf roof snow load, worked from the 50 psf ASCE 7-16 ground figure, is a starting point for an ordinary, unobstructed, heated sloped roof, not a ceiling on what a particular roof might actually be carrying.
Where snow piles up
Drift is where a roof gets into real trouble. Snow blown off a taller section lands on a lower one, piles against a wall or a parapet, or backs up below a dormer, and in each of those spots the local load can run well above the 35 psf figure that applies to an open slope. A valley between two roof planes collects the same way. None of this shows up if you only look at the ground snow load. It comes entirely from the shape of the particular roof.
Depth is not weight
A foot of snow in January is not a foot of snow in March. Fresh, light snow runs roughly 5 to 7 pounds per square foot for every foot of depth. Once it settles, or once it gets wet from a partial thaw, that same depth can weigh two to three times as much. An ice layer on top, from meltwater that refroze, adds more weight again in a much thinner layer. That is why a roof that shrugged off a deep early-season snowfall can struggle with a shallower, heavier load later in the winter.
Signs a roof is overloaded
- Interior doors that suddenly stick or won’t latch
- New cracks in ceiling drywall, especially near the middle of a span
- A ridge line that looks like it is sagging when viewed from the ground
- Popping or cracking sounds from the attic framing under load
If you see any of those, the safe response is to rake snow from the ground with a roof rake, working from the eaves inward, rather than climbing onto a loaded roof to shovel it. A loaded roof is an unpredictable place to stand, and the weight you add by standing there is exactly what the structure can least afford at that moment. Whether a specific roof is adequate for the load it’s actually carrying is a question for a local building department or a licensed engineer, not a guess made from the ground.
What wind speed must a roof withstand in Alaska?
The basic design wind speed for Anchorage is 128 mph under ASCE 7-16, for Risk Category II buildings, which covers an ordinary house. That figure is a 3-second gust measured at 33 feet in open, Exposure C terrain, not a sustained wind speed and not the kind of number a weather forecast reports. Set directly against a hurricane’s headline sustained speed it looks alarming. Set on the same 3-second-gust basis, it is simply what the structural code assumes a house at that location must resist.
No debris flag at this point
The facts available for Anchorage carry no wind-borne debris designation, so this page won’t assert that impact-rated glazing or shutters are required there on that basis. Coastal and hurricane-prone regions elsewhere in the country do carry that flag, and it is a real, costly obligation where it applies, since it requires impact-rated glazing or approved shutters on the openings. Anyone near open water, or unsure whether a local overlay applies to their property, should ask the municipal building department rather than guess from a state-level figure.
What the number actually buys
What the 128 mph figure governs is more mundane and just as consequential: the wind rating printed on a shingle package, the nailing pattern the installer follows, how the roof sheathing is fastened to the framing, and the uplift connections tying the roof structure down to the walls. Edges, rakes and ridges fail first in a wind event, because that is where uplift pressure concentrates hardest, which is why code nailing patterns are tighter in those zones than in the open field of the roof.
ASCE 7-22 maps the same Anchorage point at the same 128 mph, so this is one of the rarer cases where the newer edition doesn’t move the number at all. That stability doesn’t extend to every part of the state. Wind speed along the coast or over open water can run well above an inland reading, and a builder anywhere outside Anchorage should confirm the design value that applies locally before ordering a shingle product or a fastening schedule.
Does Alaska require an ice barrier under the shingles?
An ice barrier is a self-adhering waterproof membrane installed under the shingles, run from the eave edge up past the interior line of the exterior wall. Its job isn’t to stop snow from sitting on the roof. It’s to stop meltwater that backs up behind an ice dam from finding a seam and reaching the roof deck, where it can rot sheathing and stain the ceiling below.
Why ice dams form here
Anchorage’s coldest-month mean minimum temperature runs 11.0°F under NOAA’s 1991-2020 climate normals, cold enough, combined with a roof snow load that sits in place for months, for melt-and-refreeze cycles to matter. Other parts of the state, particularly the interior and the north, run considerably colder in winter, which only sharpens the same mechanics. An ice dam forms when heat escaping from a warm attic melts the underside of the snowpack, the meltwater runs down to the cold eave overhang beyond the heated wall line, and refreezes there, building a ridge of ice that backs water up under the shingles above it. The membrane exists for that exact moment. It doesn’t stop the dam from forming, only from doing damage once it has.
Who actually decides this
Alaska has no statewide residential building code. The code the State Fire Marshal administers expressly excludes detached one-, two- and three-family houses and townhouses of three stories or fewer, so no state agency sets this rule for the whole state. Adoption of a residential code, including any ice barrier requirement, is left to individual municipalities such as Anchorage, so the answer for a given house depends on which code edition, if any, that municipality has adopted, not on a single statewide mandate. A state energy standard applies only where a project uses state housing finance, which is a separate matter from the building code question.
That local structure means the honest answer is to check with the municipal building department where the roof actually sits. Readers as far north as the Yukon’s roof snow load and wind rules page face a comparably cold, snow-heavy climate and the same underlying physics, even where the administering code differs from Alaska’s municipal system.
Whether or not a membrane ends up required locally, the more durable fix for ice damming is attic air sealing and insulation, not the membrane on its own. A well-sealed, well-insulated attic keeps the underside of the roof deck close to outdoor temperature, so the snowpack has less reason to melt from below in the first place. A membrane without that work protects the deck from a dam that keeps re-forming every winter. The insulation is what stops the dam itself.
What roofing material suits Alaska best?
The honest answer starts from the same three figures already on this page: a roughly 35 psf roof snow load worked from Anchorage’s 50 psf ASCE 7-16 ground figure, a 128 mph basic design wind speed, and an IECC climate zone that varies sharply across the state. Of the state’s 27 counties, 11 fall in zone 7, 8 in zone 8, 5 in zone 6A and 3 in zone 5C. No single material answers all three loads at once, and this page won’t name one as universally best without saying what it’s best at.
Comparing the options
| Material | What it does well here | What it adds to the load picture |
|---|---|---|
| Architectural asphalt shingles | Wind rating is printed on the package and matched to a fastening schedule | Light dead load, but performance depends entirely on the nailing pattern actually used |
| Standing-seam metal | Sheds accumulated snow well once it lets go | Sliding snow lands somewhere, and that spot needs a snow guard or a clear path, not a doorway or walkway |
| Slate or concrete tile | Heavy, durable surface | Its own dead weight is added on top of the snow load the structure already carries |
Where wind governs the design, the fastening and the underlayment matter more than which material sits on top. A shingle rated for a high wind speed performs only as well as the nailing pattern it was actually installed with. A high-rated product nailed to a lower standard behaves like the lower standard once it’s on the roof, and the same logic applies to a metal roof’s seam spacing and clip attachment.
The climate zone spread across the state also shapes the roof assembly around whichever material gets chosen, particularly the attic insulation and air sealing discussed above, since a zone 8 county carries a colder design condition than a zone 5C one and the ice-damming risk shifts with it. States with a much lighter design load, like the New Mexico’s roof snow load and wind rules page describes, turn these material trade-offs mostly on heat and UV exposure instead of snow and wind, which is exactly why a recommendation built for that climate doesn’t transfer here.
Before committing to a material for a specific roofing project, get the site-specific ground snow load, wind speed and climate zone confirmed by the municipal building department, since all three shift with elevation and location even within a single Alaska community.