New York’s snow load number that gets quoted everywhere, 20 psf, is a New York City figure measured on the ground, not a statewide number and not the load a rafter actually carries. Ask your local building department for the figure your specific permit uses, because elevation and lake-effect snow push the real number far higher north and west of the city.
What is the ground snow load in New York?
The design ground snow load mapped for New York City is 20 psf under ASCE 7-16, the edition referenced by the 2021 editions of the IRC and IBC that most states use as their baseline for this kind of figure. That is the number a permit application and a plan reviewer start from. It is not, on its own, what a roof is built to hold.
Ground snow load describes snow sitting on open, level ground. Before it becomes a design number for a rafter or a truss, the code runs it through exposure, thermal and slope factors that account for wind scour, heated versus unheated space, and how steep the roof is. For an ordinary heated sloped house roof, that conversion lands the New York City figure at roughly 14 psf of roof snow load, the value that actually shows up on a truss drawing.
ASCE 7-22, the newer edition a handful of jurisdictions are starting to adopt, maps the same New York City point at 46 psf. That is not three times the snow. ASCE 7-22 works on a strength-level basis with a 1.0 load factor, while ASCE 7-16 is a nominal value used with a 1.6 load factor, so the two numbers are not measuring the same thing and the gap says nothing about worsening winters or undersized existing roofs.
Both figures apply to New York City specifically. Snow loading in New York varies enormously with elevation and with proximity to the Great Lakes, so a number measured at sea level in Manhattan tells you nothing about a roof in the Adirondacks or the Tug Hill Plateau. It’s also worth knowing that New York City issues building permits under its own construction codes, separate from the Uniform Code that the state’s Department of State administers for the rest of New York, so the specific edition your local plan reviewer works from can differ by jurisdiction even though the mapped figure itself does not.
How much snow can a roof hold in New York?
There’s no single number that answers this, because the load a roof actually experiences depends on the roof’s shape as much as on how much snow falls. Working from the New York City ground figure of 20 psf, an ordinary heated sloped roof lands near 0.7 of that, roughly 14 psf, and a steeper roof sheds load faster and carries less still.
Drift is where that arithmetic falls apart, and it’s also where roofs actually fail. Snow blown off a taller section of roof piles up against a wall, behind a parapet, below a dormer, or in a valley between two roof planes, and a lower roof sitting next to a taller one can see drift loads several times the flat-roof figure. None of that shows up if you only look at the ground snow load number.
Depth is not weight
The other trap is treating a foot of snow as a fixed weight. It isn’t. Fresh, light snow runs roughly 5 to 7 pounds per square foot for every foot of depth. Once it settles or takes on water, that figure roughly doubles or triples. An ice layer on top adds more weight again in a much thinner layer than the snow it replaced.
| Snow condition | Approximate weight per foot of depth |
|---|---|
| Fresh, dry snow | 5-7 lb per sq ft |
| Settled or wet snow | 2-3 times fresh snow |
| Ice layer | Heavier still, concentrated in a thin layer |
That’s why a foot of snow in late January is not the same load as a foot of snow in March that’s been through a thaw-refreeze cycle. Watch for interior doors that suddenly stop closing, new cracks running across ceiling drywall, or a ridge line that looks like it’s dipping. Any of those is a reason to call a professional, not a reason to guess. Raking snow off from the ground with a roof rake is the safe response to a heavy accumulation. Climbing onto a loaded roof to shovel it is not, and it’s how a lot of winter roof injuries happen. The same elevation-driven swing shows up on the page covering roof snow load and wind speed rules in Utah, where mountain valleys push the ground figure up sharply over a short distance, much the way New York’s own high country departs from the New York City number.
What wind speed must a roof withstand in New York?
The basic design wind speed mapped for New York City is 115 mph under ASCE 7-16, for Risk Category II, the classification that covers ordinary houses. That figure is a 3-second gust measured at 33 feet in open (Exposure C) terrain, not a sustained wind speed and not the number you hear quoted after a storm on the news. Comparing it directly to a hurricane’s headline wind speed makes the code look weaker than it is, because the two numbers are measured completely differently.
New York City sits in a hurricane-prone region, but it falls below the threshold that triggers the wind-borne debris requirement. That means the map alone does not require impact-rated glazing or approved shutters here, unlike in coastal zones further south where that threshold is crossed. ASCE 7-22 maps the same location at 116 mph, essentially the same figure under the newer edition, offered here only as the coming reference point rather than the governing number.
What the number actually governs
The design wind speed drives several concrete decisions on a roof: the wind rating stamped on a bundle of shingles, the nailing pattern the manufacturer specifies to hit that rating, how the sheathing is fastened to the rafters, and the uplift connections tying the roof structure down to the walls. A shingle rated for high wind performs no better than a low-wind installation if it’s nailed to a lower standard than the rating assumes.
- Ridges and hips take the highest suction as wind separates over the peak
- Rakes and eaves are where uplift first pries a shingle edge loose
- Corners of the roof plane see concentrated pressure from turning wind
Those are also the areas building inspectors look at hardest, because that’s where a poorly fastened roof actually comes apart in a storm. The 115 mph figure belongs to New York City specifically. Coastal Long Island and higher terrain elsewhere in the state see different mapped values, so confirm the number for your own location with your local building department before assuming the city figure applies.
Does New York require an ice barrier under the shingles?
An ice barrier is a self-adhering waterproof membrane installed under the shingles, run from the edge of the eave up to a point 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 working its way under the shingles and into the roof deck.
Why New York’s climate makes this a real question
New York City’s mean minimum temperature in the coldest month is 27.9°F, according to NOAA’s NCEI 1991-2020 climate normals for the New York City reference station. Combined with a design snow load that puts real accumulation on roofs most winters, that’s a climate where the conditions for ice damming, cold air outside, sustained snow cover, and a warm attic underneath, show up regularly. Further north and at higher elevation in the state, winters run colder still, which raises the same risk.
The mechanism matters more than the membrane. An ice dam forms when heat escaping 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 unheated eave overhang, where it refreezes and builds a ridge of ice. Water backs up behind that ridge and finds its way under the shingles. The ice barrier membrane protects the deck from that backed-up water. It does nothing to stop the dam from forming in the first place. Only air sealing the attic floor and adding sufficient insulation stop the heat loss that causes the dam. A roof with a membrane and a leaky, poorly insulated attic still gets an ice dam every winter, it just doesn’t leak into the ceiling below it. The same distinction between the membrane and the actual cause is covered on the page for roof snow load and ice barrier rules in Alberta, where the prairie cold makes attic heat loss the dominant driver of ice dam formation as well.
New York’s own building code is the 2025 Residential Code of New York State, part of the 2025 Uniform Fire Prevention and Building Code, itself a derivative of the 2024 International Residential Code. It functions as a statewide minimum that individual municipalities may exceed, and it’s administered by the New York State Department of State, Division of Building Standards and Codes, effective December 31, 2025. New York City, notably, runs its own construction codes outside that Uniform Code entirely. For the county-level insulation levels that reduce the attic heat loss behind ice damming, check where your county falls among New York’s three IECC climate zones under the 2021 IECC, zone 5A covers 36 counties, zone 6A covers 18, and zone 4A covers 8, since the required insulation level differs by zone and a county-level check is the only way to get the right row of the table.
What roofing material suits New York best?
The combination that matters here is New York City’s roof snow load near 14 psf, its 115 mph design wind speed, and a climate spanning IECC zones 4A, 5A and 6A across the state. That combination doesn’t crown a single best material, it changes what each option has to be good at.
Architectural asphalt shingles are rated by wind speed at installation, and that rating only holds if the nailing pattern matches the manufacturer’s specification for the rating claimed, an easy detail to shortcut and a costly one to get wrong. Standing-seam metal roofing sheds snow far more readily than shingles, which reduces the standing load on the roof itself but creates a new problem: that shed snow and ice has to land somewhere, and a design that dumps it over a doorway, a walkway or a driveway is a planning failure, not bad luck. Slate and concrete tile add substantial dead weight of their own on top of whatever snow load the structure already carries, so a switch to either material on an existing structure is a structural question, not just a finish choice.
| Material | Snow behavior | What it adds to the load equation |
|---|---|---|
| Architectural asphalt shingles | Holds snow in place, doesn’t shed | Wind rating depends entirely on correct nailing |
| Standing-seam metal | Sheds snow and ice readily | Requires a planned drop zone clear of doors and walkways |
| Slate or concrete tile | Holds snow, minimal shedding | Adds significant dead weight on top of snow load |
Where wind governs the design, as it does across most of New York, the fastening and the underlayment underneath the visible material matter more than which material sits on top. A high-wind-rated shingle installed with the wrong nail pattern, or sheathing fastened to a lower standard than the roof’s uplift connections assume, performs at the lower standard regardless of what the shingle wrapper claims. Anyone starting a re-roof project from scratch should work through the general planning steps covered under roofing before choosing a material, since the load and wind figures on this page only make sense once the underlying structure and fastening plan are already sound.