By The Roofing Brief Team. Last reviewed: October 2026.
How much snow a roof can hold comes down to weight: most residential roofs can carry about 20 pounds per square foot (psf) of snow before they become stressed, per IBHS guidance summarized by the DOE Building America Solution Center. That is roughly 4 feet of fresh snow, about 2 feet of old packed snow, or 11 to 12 inches of heavy wet snow at the 21 psf per foot that FEMA P-957 (2013) gives for wet snow. Roofs in heavy-snow regions are built for more by code, and ground snow loads above 70 psf take the design outside the IRC span tables and onto a structural engineer.
This report compiles that load math with Aon insured-loss data published by the Insurance Information Institute and documented collapse events; figures we derived ourselves are labeled as Roofing Brief calculations.
Executive summary
- Most residential roofs are built to carry about 20 pounds per square foot (psf) of snow before they become structurally stressed, according to the DOE Building America Solution Center, citing IBHS (2021).
- Snow weight varies enormously by type. One foot of light, dry snow weighs about 3 psf, while one foot of heavy, wet snow weighs about 21 psf, and one foot of ice weighs about 57 psf (U.S. Department of Energy, Building America Solution Center).
- Winter storms produced about 43.2 billion dollars in nominal U.S. insured losses across 2016 through 2025, an average near 4.3 billion dollars per year (Roofing Brief calculation from Aon data in the Insurance Information Institute winter storm fact page).
- The February 2021 polar vortex and Texas freeze remains the costliest U.S. winter event since 1950 at 15.0 billion dollars in insured losses, or 18.52 billion dollars in 2025 dollars (Aon, via Insurance Information Institute).
- ASCE 7-22 moved to strength-level ground snow loads: in Baltimore, pg went from 25 psf (with a 1.6 load factor) in ASCE 7-16 to 60 psf (with a 1.0 load factor) for Risk Category II, per Structure magazine.
- In the February 2015 Boston-area storms, the Massachusetts Emergency Management Agency tallied 128 failed roofs in two weeks, up from 106 two days earlier (Insurance Journal, February 23, 2015).
- Winter roof risk is regional: a roof framed from IRC span tables is limited to ground snow loads of 70 psf or less, and sites above that need an engineered design under ASCE 7 (DOE Building America Solution Center).
Key findings
- One foot of light, dry snow weighs about 3 psf; one foot of heavy, wet snow weighs about 21 psf (FEMA P-957, 2013, via the DOE Building America Solution Center).
- One foot of ice weighs about 57 psf, and one inch of ice weighs about 5 psf (U.S. Department of Energy, Building America Solution Center).
- One inch of liquid water equals 5.2 psf, the physical constant behind every roof snow-load estimate (National Weather Service snow-measurement guidance; 62.4 pounds per cubic foot of water).
- Ten to twelve inches of fresh snow is roughly one inch of water, or about 5 psf on the roof (U.S. Department of Energy, Building America Solution Center).
- Most residential roofs should support about 20 psf of snow before becoming stressed, regardless of location (U.S. Department of Energy, Building America Solution Center).
- Two feet of old snow plus two feet of new snow can weigh as much as 60 psf, beyond the typical capacity of most roofs (U.S. Department of Energy, Building America Solution Center).
- ASCE 7-22 converts ground snow load to flat-roof snow load with Equation 7.3-1, pf = 0.7 x Ce x Ct x pg, so a site with pg of 60 psf and Ce and Ct of 1.0 gets a flat-roof load of 42 psf; ASCE 7-16 and earlier also multiplied by an importance factor, Is (Structure magazine).
- Under ASCE 7-22 the Baltimore Risk Category II ground snow load is 60 psf at a 1.0 load factor, versus 25 psf at a 1.6 factor in ASCE 7-16, a 30% rise in total roof load with a 15 psf dead load (Structure magazine, Ground Snow Loads for ASCE 7-22).
- Ground snow loads above 70 psf exceed International Residential Code span tables and require a structural engineer under ASCE 7 (U.S. Department of Energy, Building America Solution Center).
- U.S. winter-storm insured losses totaled 15.53 billion dollars in 2021 and 10.20 billion dollars in 2022, the two highest years in the 2016 through 2025 record, while 2025 came in near 1.39 billion dollars (Aon, via Insurance Information Institute).
- The February 12 to 20, 2021 Texas freeze caused 15.0 billion dollars in insured losses, the top entry in the Aon list of U.S. winter events since 1950 (Aon, via Insurance Information Institute).
- State Farm paid more than 472 million dollars in frozen-pipe claims nationwide in 2021, nearly eight times its 2020 total, and the February 2021 storm moved Texas to the top state for those claims (State Farm newsroom).
- The Minneapolis Metrodome inflatable roof collapsed on December 12, 2010, after a storm that dropped more than 17 inches of snow (MPR News, Associated Press).
- Winter Storm Fern (January 2026) caused about 3.5 billion dollars in insured losses and 4.6 billion dollars in economic losses, potentially the fourth-costliest U.S. winter storm on record, per Aon’s Q1 2026 catastrophe report.
How much snow a roof can hold: the load math
A roof does not respond to snow depth. It responds to snow weight. Two roofs under the same 18 inches of snow can face completely different loads depending on whether that snow is dry powder or wet, refrozen pack. The controlling variable is water content, and the controlling constant is that one inch of liquid water weighs 5.2 psf.
The table below shows how much each snow and ice type weighs per foot of depth. Values are from FEMA P-957 (2013) and IBHS (2021) as compiled by the DOE Building America Solution Center.
| Material on the roof | Approximate weight | Source |
|---|---|---|
| Fresh light, dry snow, per foot | 3 psf | DOE Building America |
| Heavy, wet snow, per foot | 21 psf | DOE Building America |
| Ice, per foot | 57 psf | DOE Building America |
| Ice, per inch | about 5 psf | DOE Building America |
| Fresh snow, 10 to 12 inches | about 5 psf | DOE Building America |
| Packed snow, 3 to 5 inches | about 5 psf | DOE Building America |
| Liquid water, per inch | 5.2 psf | National Weather Service |
Density figures support the same picture. Fresh snow runs about 3 to 5 pounds per cubic foot, packed snow about 12 to 26 pounds per cubic foot, and ice about 57 pounds per cubic foot (Rimkus commercial roof snow-load review). The practical lesson is that the same depth of snow can weigh four to seven times more once it settles, gets rained on, or refreezes.
FEMA P-957 advises leaving at least a couple of inches of snow on the roof, using plastic rather than metal shovels, and clearing drifts at parapets and roof steps first. For the full workflow, see our guide on flat roof snow removal and the load math and our roundup of the best roof snow rakes for ground-level clearing.
When to clear the roof: snow load thresholds
| If the roof carries… | Approximate load | Action |
|---|---|---|
| Up to about 4 feet of fresh, light snow | About 20 psf (10 to 12 inches of fresh snow is about 5 psf) | At the general residential limit; plan clearing before more snow or rain arrives |
| More than about 2 feet of old, packed snow | Over 20 psf (3 to 5 inches of packed snow is about 5 psf) | Clear with a roof rake from the ground or hire a snow removal contractor |
| About 1 foot of heavy, wet snow | About 21 psf | Clear now; rain on snow raises the load further |
| 2 feet of old snow plus 2 feet of new snow | Up to about 60 psf | Beyond most roofs’ typical capacity; clear or keep people out of the space |
| Ice at the eaves (ice dam) | About 5 psf per inch of ice | Treat 4 inches of ice as about 20 psf concentrated at the edge |
| Any FEMA P-957 warning sign (sagging ceiling, sprinkler heads dropping, jammed doors, popping sounds) | Any | Evacuate and call the local building authority or a design professional |
Load figures are from FEMA P-957 (2013) and IBHS (2021) as compiled by the DOE Building America Solution Center; the 20 psf benchmark is a general residential figure, not the engineered capacity of any specific roof.
What overloads a roof
The most-cited design threshold is simple. Most residential roofs should carry about 20 psf of snow before they become stressed (IBHS 2021, via the DOE Building America Solution Center). That is a general figure, not a code value for any specific building; in snow regions the IRC sizes rafters from local ground snow loads up to 70 psf.
Danger arrives when accumulation, drifting, and refreezing push the load past the design number. Two feet of old snow plus two feet of new snow can weigh as much as 60 psf, beyond the typical capacity of most roofs (U.S. Department of Energy, Building America Solution Center). FEMA P-957 lists unbalanced drifting and sliding snow, rain-on-snow, and meltwater ponding on low-slope roofs as leading causes of snow-load failures, with parapets, stepped roofs and rooftop equipment as the usual drift traps.
FEMA P-957 lists 10 warning signs of an overstressed roof, including sagging ceiling tiles or sprinkler lines, sprinkler heads deflecting below suspended ceilings, popping or creaking noises, bowing truss chords, doors and windows that stop closing, cracks in walls or masonry, and severe roof leaks. FEMA says any one of them calls for prompt evacuation and a structural inspection by the local building authority or a qualified design professional. If snow or ice has already caused damage, see our guide to roof repair in winter for what can be fixed safely before spring.
Snow is one of 4 winter hazards in Aon’s winter-storm category, which counts snow, ice, freezing and flooding. For the full range, see our overview of the types of roof damage and how coverage typically applies.
Regional snow-load differences
Roof snow requirements are not national. They are set locally from a ground snow load, pg, that varies by an order of magnitude across the country. ASCE 7-22 then reduces the ground value to a design flat-roof load with Equation 7.3-1, pf = 0.7 x Ce x Ct x pg, adjusting for wind exposure and thermal condition. Building importance is now built into separate ground snow load maps for each risk category, replacing the Is factor that ASCE 7-16 and earlier editions applied in the same equation. Our guide to roof snow load design requirements works through that conversion step by step.
ASCE 7-22 changed the numbers themselves. Its ground snow loads are reliability-targeted, strength-level values used with a 1.0 load factor, so they read higher than the older allowable-level maps that used a 1.6 factor. Look up a site’s value in the ASCE Hazard Tool or the local amendment rather than reusing an old map figure.
| Item | Value | Source |
|---|---|---|
| Baltimore, Risk Category II, ASCE 7-16 pg | 25 psf (x 1.6 load factor) | Structure magazine |
| Baltimore, Risk Category II, ASCE 7-22 pg | 60 psf (x 1.0 load factor) | Structure magazine |
| Change in total roof load, 15 psf dead load | About +30% | Structure magazine |
| Baltimore County local minimum roof snow load | 30 psf (48 psf factored) | Structure magazine |
| Flat-roof load, worked example at pg 60 psf, Ce and Ct of 1.0 | 0.7 x 1.0 x 1.0 x 60 = 42 psf | ASCE 7-22 Equation 7.3-1; Roofing Brief calculation |
| IRC span-table limit | Ground snow load of 70 psf or less | DOE Building America Solution Center (IRC R301.2, R802) |
Above a 70 psf ground snow load, or for framing the IRC R802 span tables do not cover, a structural engineer has to verify the design under ASCE 7. Lake-effect and mountain sites often carry site-specific case-study values that local building departments publish as amendments.
What winter roof failures cost
Aon’s winter-storm category counts snow, ice, freezing and flooding, so it includes burst pipes and ice-dam water damage along with roof collapse; roof structural failure is a subset. In 2025 the category totaled about 1.39 billion dollars, the fourth-lowest year of the last ten.
| Year | Insured losses (nominal) | In 2025 dollars |
|---|---|---|
| 2016 | 1.18 billion dollars | 1.61 billion dollars |
| 2017 | 926 million dollars | 1.23 billion dollars |
| 2018 | 3.79 billion dollars | 4.94 billion dollars |
| 2019 | 1.86 billion dollars | 2.39 billion dollars |
| 2020 | 1.10 billion dollars | 1.38 billion dollars |
| 2021 | 15.53 billion dollars | 19.17 billion dollars |
| 2022 | 10.20 billion dollars | 11.29 billion dollars |
| 2023 | 3.33 billion dollars | 3.59 billion dollars |
| 2024 | 3.93 billion dollars | 4.14 billion dollars |
| 2025 | 1.39 billion dollars | 1.40 billion dollars |
Source: Aon, via Insurance Information Institute, Facts and Statistics: Winter storms (2016 to 2025 table, accessed October 2026).
The four costliest U.S. winter events since 1950, adjusted to 2025 dollars, are the February 2021 polar vortex and Texas freeze at 18.52 billion dollars (15.0 billion nominal), the December 2022 winter storm at 8.43 billion dollars (7.7 billion nominal), the March 1993 blizzard at 4.52 billion dollars (2.0 billion nominal), and the February 2015 Northeast storms at 2.91 billion dollars (2.1 billion nominal) (Aon, via Insurance Information Institute).
Insurer data shows how the freeze lands on homes. State Farm paid more than 472 million dollars in frozen-pipe claims in 2021, nearly eight times its 2020 total, with Texas the top state after the February storm. Winter Storm Fern in January 2026 added about 3.5 billion dollars of insured losses, per Aon’s Q1 2026 report.
Against a 15.0 billion dollar event, clearing a loaded roof is a small line item; for typical pricing, see our guide to roof snow removal cost.
Notable roof collapse events
Large collapses concentrate in fast, heavy, or repeated snowfalls that outrun a roof’s design load. The Minneapolis Metrodome inflatable roof collapsed on December 12, 2010, after a storm that dropped more than 17 inches of snow, forcing the NFL to relocate a Vikings home game (MPR News, Associated Press). The failure of an air-supported roof under a single heavy storm shows how quickly accumulated weight overwhelms a structure not designed for that load path. If you are hiring in Minnesota, we rank roofers in Minneapolis and Duluth.
The 2015 New England winter produced a cluster of failures rather than one landmark event. The Massachusetts Emergency Management Agency tallied 128 failed roofs in the two weeks to February 22, 2015, up from 106 two days earlier, mostly over warehouses and barns, and expected the count to climb (Insurance Journal, February 23, 2015). Aon’s list puts the February 2015 storms at 2.1 billion dollars in insured losses. The pattern that winter was repeated storms with little melt between them, letting old and new snow stack toward the 60 psf combined load that exceeds most roof capacities. If you are hiring in Massachusetts, see our pages on roofers in Amherst and Pittsfield.
Roofing Brief original calculations
The following figures are original Roofing Brief calculations derived from the cited public inputs. They are analytical estimates, not published statistics, and they use general design values rather than any specific building’s engineered capacity.
1. Water-equivalent capacity of a 20 psf roof
Using the physical constant that one inch of liquid water weighs 5.2 psf, a roof rated near the 20 psf general residential threshold is fully loaded at about 3.85 inches of water equivalent (20 divided by 5.2). Inputs: National Weather Service water constant; DOE Building America 20 psf general threshold. Limitation: real roofs vary widely, and code capacity in snow regions is often far higher.
2. Depth of wet snow that reaches design load
At about 21 psf per foot for heavy, wet snow, a 20 psf general design load is reached by roughly 11 to 12 inches of wet snow (20 divided by 21 equals 0.95 foot). By contrast, at about 3 psf per foot for light, dry snow, it would take more than 6 feet of dry powder to reach the same 20 psf. Inputs: DOE Building America snow weights; DOE 20 psf general threshold. Limitation: assumes uniform, balanced load and ignores drifting.
3. Ice-equivalent to design load
At about 5 psf per inch of ice, roughly 4 inches of solid ice reaches the 20 psf general design load (20 divided by 5). This illustrates why ice dams and refrozen layers are disproportionately dangerous relative to their thickness. Inputs: DOE Building America ice weight; DOE 20 psf general threshold. Limitation: ice loads are usually localized at eaves and valleys, not uniform.
4. Decade winter-storm insured-loss total and concentration
Summing the annual Aon figures for 2016 through 2025 gives about 43.2 billion dollars in nominal U.S. winter-storm insured losses, an average near 4.3 billion dollars per year. In 2025 dollars the decade total is about 51.1 billion dollars, and the single year 2021 (19.17 billion) accounts for about 37 percent of that real total. Inputs: Aon annual winter-storm insured losses, via Insurance Information Institute. Limitation: winter-storm losses include burst pipes, wind, and freeze damage, not roof collapse alone.
Recommended charts
- Snow weight by type, per foot of depth. Data: DOE Building America psf-per-foot values for dry snow, wet snow, and ice. Insight: wet snow and ice weigh 7x to 19x more than dry powder at equal depth. Citation-worthy because it reframes roof risk around weight, not inches.
- U.S. winter-storm insured losses by year, 2016 to 2025. Data: Aon annual figures via Insurance Information Institute. Insight: 2021 and 2022 dwarf the rest of the decade. Citation-worthy as a clean time series with named source.
- ASCE 7-16 versus ASCE 7-22 ground snow load. Data: Structure magazine Baltimore example, 25 psf (x 1.6) versus 60 psf (x 1.0). Insight: total roof load rises about 30% with a 15 psf dead load. Citation-worthy for code-change context.
- Inches to reach 20 psf by snow type. Data: Roofing Brief calculations from DOE weights. Insight: 6 feet of powder versus 12 inches of wet snow versus 4 inches of ice. Citation-worthy as an original derived comparison.
Methodology
Sources were selected in this priority order: federal agencies and national design standards first, then insurance and catastrophe-modeling datasets, then reputable trade and news reporting for event documentation. Structural and snow-weight figures come from the DOE Building America Solution Center (citing FEMA P-957 and IBHS), ASCE 7 provisions as explained in Structure magazine, and National Weather Service measurement guidance. Loss figures come from Aon via the Insurance Information Institute, Aon’s Q1 2026 catastrophe report, and the State Farm newsroom.
Inclusion required a named, verifiable public source fetched during this research. Where two sources disagreed, the primary or standards source was used and the discrepancy noted. One example: the Insurance Information Institute page describes the December 2022 storm as 8.4 billion dollars in its narrative and 7.7 billion nominal (8.43 billion in 2025 dollars) in its table; this report uses the table figures. Derived figures are labeled as Roofing Brief calculations with their inputs and limitations. In the October 2026 review, figures that could not be re-verified (a per-home burst-pipe average, a Texas-only claims total, regional collapse counts and a city snow-load table) were removed. Last updated October 2026.
Source quality ranking
- Tier 1, primary sources and standards: DOE Building America Solution Center; FEMA P-957 Snow Load Safety Guide (2013); ASCE 7-22 snow-load provisions; National Weather Service snow-measurement guidance.
- Tier 2, insurance and catastrophe data: Aon annual insured-loss figures via the Insurance Information Institute; Aon Q1 2026 catastrophe report; State Farm claims disclosures.
- Tier 3, reputable journalism and expert commentary: Insurance Journal, MPR News and Associated Press for collapse-event documentation; Rimkus and Structure magazine for engineering context.
- Excluded: unsourced calculators, AI-generated roundups, and blog posts without a traceable primary reference.
Journalist-friendly additions
Most quotable statistics
- One foot of heavy, wet snow weighs about 21 psf, seven times the roughly 3 psf of one foot of dry powder (DOE Building America).
- Most residential roofs are stressed at about 20 psf of snow, and two feet of old plus two feet of new snow can hit 60 psf (DOE Building America).
- U.S. winter storms caused about 43.2 billion dollars in insured losses across 2016 to 2025 (Roofing Brief calculation from Aon data).
- Massachusetts tallied 128 failed roofs in two weeks of February 2015 storms (MEMA, via Insurance Journal).
Data limitations
Winter-storm insured-loss totals bundle burst pipes, ice-dam water damage, wind, and freeze losses with any structural roof failure, so they overstate roof-collapse-specific costs. There is no single national registry of roof collapses, so event counts come from state agencies and news reporting and are likely undercounts. The 20 psf figure is a general residential rule of thumb, not a code value for any specific building; engineered capacity in snow regions is often far higher. ASCE 7-22 ground snow loads are site-specific strength-level values, so the Baltimore example (60 psf) illustrates the code change rather than any other city.
Downloadable dataset recommended fields
For a 10-year (2016 to 2025) file: state or metro; ASCE 7-22 ground snow load (pg, psf); design flat-roof load (pf, psf); representative roof design capacity (psf); snow type; measured depth (inches); estimated load (psf); winter-storm insured losses by year (nominal and inflation-adjusted); reported roof collapses; source; year; methodology note.
Press summary (about 150 words)
A roof does not fail because of snow depth. It fails because of snow weight. One foot of light powder weighs about 3 pounds per square foot, but one foot of wet snow weighs about 21 pounds, and one foot of ice about 57, according to U.S. Department of Energy Building America guidance. Most homes are built to hold roughly 20 pounds per square foot of snow, so two feet of old snow topped by two feet of new can reach 60 pounds and exceed that limit. The financial stakes are large. Aon data via the Insurance Information Institute show U.S. winter storms caused about 43.2 billion dollars in insured losses from 2016 to 2025, led by the 15.0 billion dollar Texas freeze of February 2021. In February 2015, Massachusetts tallied 128 failed roofs in two weeks.
Five suggested headlines
- How Much Snow Can Your Roof Hold Before It Fails, by the Numbers
- A Foot of Wet Snow Weighs Seven Times More Than Powder: The Roof Math
- Winter Storms Cost 43 Billion Dollars in a Decade: The Roof Data
- The 20 Pound Rule: When Snow Turns a Roof Into a Hazard
- From the Metrodome to New England: What Roof Collapses Teach About Snow Load
Frequently asked questions
Ten answers follow in the FAQ, each carrying the psf figure or dollar total behind it.
FAQ
How much snow can a roof hold before it collapses?
Most residential roofs can hold about 20 pounds per square foot of snow before they become stressed, per IBHS guidance summarized by the DOE Building America Solution Center. That is roughly 4 feet of fresh snow, about 2 feet of packed snow, or 11 to 12 inches of wet snow. Roofs in heavy-snow regions are designed for more by code.
How much does a foot of snow weigh on a roof?
One foot of light, dry snow weighs about 3 pounds per square foot, and one foot of heavy, wet snow weighs about 21 pounds per square foot (FEMA P-957, 2013, via the DOE Building America Solution Center).
How much does ice weigh on a roof?
One foot of ice weighs about 57 pounds per square foot, and one inch of ice weighs about 5 pounds per square foot, so 4 inches of ice at the eaves equals the 20 psf general residential benchmark (DOE Building America Solution Center).
How many inches of snow is dangerous for a roof?
At the general 20 pound per square foot benchmark, roughly 11 to 12 inches of wet snow, about 2 feet of old packed snow, or about 4 inches of ice reaches that load, while light powder would need about 4 feet or more (Roofing Brief calculations from FEMA P-957 and IBHS weights).
How do I estimate the snow load on my roof?
Multiply the snow’s water content by 5.2 pounds per square foot per inch of water. Ten to twelve inches of fresh snow is about one inch of water, or roughly 5 pounds per square foot, and 3 to 5 inches of packed snow is about the same (DOE Building America Solution Center and National Weather Service).
What are the warning signs a roof is overloaded by snow?
FEMA P-957 lists sagging ceiling tiles or sprinkler lines, sprinkler heads dropping below suspended ceilings, popping or creaking noises, bowing truss chords, doors and windows that stop closing, cracks in walls and severe leaks. FEMA says any one of them calls for evacuation and an inspection by the local building authority or a design professional.
What is the costliest U.S. winter storm on record?
The February 2021 polar vortex and Texas freeze, with 15.0 billion dollars in insured losses, or 18.52 billion dollars in 2025 dollars, tops Aon’s list of U.S. winter events since 1950 (Aon, via Insurance Information Institute).
How much do winter storms cost in insured losses each year?
U.S. winter storms averaged about 4.3 billion dollars per year in nominal insured losses from 2016 to 2025, totaling about 43.2 billion dollars over the decade, with a low of about 926 million dollars in 2017 and a high of 15.53 billion dollars in 2021 (Roofing Brief calculation from Aon data via the Insurance Information Institute).
Does home insurance cover roof collapse from snow?
Many homeowners policies cover sudden collapse caused by the weight of ice, snow or sleet, but wording varies by form, insurer and state. Read the Collapse additional coverage and the weight-of-ice-and-snow peril in your own policy, and ask the insurer whether gradual deterioration or a roof past a stated age is excluded.
Why do roofs collapse more in wet snow and repeated storms?
Wet snow weighs about 21 pounds per square foot per foot of depth, seven times the 3 psf of dry powder, and back-to-back storms let 2 feet of old snow and 2 feet of new snow stack toward 60 pounds per square foot, beyond most roof capacities (DOE Building America Solution Center).