How much does snow weigh?

Fresh fluffy snow weighs about 3-7 lbs per cubic foot. Settled snow weighs 10-20 lbs/cu ft. Packed snow 20-40 lbs. Ice 50-62 lbs/cu ft. A typical 12 inches of settled snow weighs about 15 psf on the roof. A foot of wet, dense snow can weigh 20+ psf.

What is a safe snow load for a roof?

Most residential roofs are designed for 20-40 psf ground snow load. Building codes vary by region: 5-10 psf in southern US, 20-40 psf in Midwest, 30-50 psf in New England, 50-100+ psf in heavy-snow areas. Consult local codes for your specific design load.

Does roof pitch affect snow load?

Yes, steeper roofs shed snow more easily. Building codes allow snow load reductions for roofs with pitch greater than about 30 degrees (7/12 pitch). At very steep pitches (45° / 12/12), the load reduction can be 20-30%. Flat and low-pitch roofs use the full design load with no reduction.

How do I measure snow depth on my roof?

Use a long stick or roof rake from the ground to probe the snow. Take measurements at several spots — depth varies due to drifting and wind. The deepest area (often the leeward side) is the critical measurement. Avoid climbing on the roof to measure; falls are common.

When should I remove snow from my roof?

Watch for: snow exceeding 1 foot on flat/low-pitch roofs; ice dams forming; snow load reaching 50-75% of design capacity (15-30 psf for residential); structural distress (cracking, sagging). Use a roof rake from the ground when possible; hire pros for steep roofs or significant accumulation.

How does drifting affect snow load?

Wind drifts snow significantly. The leeward (downwind) side of a roof can accumulate 2-3× the average snow depth. Areas behind roof obstacles (HVAC units, chimneys) accumulate more. Lower roof sections adjacent to higher ones can pile up. Building codes specify drift load multipliers for design.

Can I get insurance coverage for snow damage?

Yes, most homeowner insurance covers snow-related roof damage including collapse. However, you must maintain your home reasonably — failing to clear excessive snow may void coverage. Document snow conditions before/during heavy accumulation. Take photos of any concerning structural changes.

Snow Load Calculator

Estimate the snow load on your roof in pounds per square foot (psf) based on snow depth and snow density. Compare against common building code limits and see the total weight on your roof area.

Snow load on roofs is a serious structural concern in cold climates. A foot of fresh snow weighs about 5 pounds per square foot; wet, packed snow can exceed 20 psf; ice can hit 50+ psf. Multiply that by a typical 1500-2000 sq ft roof and you have thousands of pounds of weight that the roof structure must support. Building codes specify design snow loads ranging from 20 psf in mild climates to 100+ psf in heavy-snow regions like New England and Alaska.

This calculator returns snow load in pounds per square foot (psf) and total weight on the roof. Snow depth and density determine the load. Fresh fluffy snow at 5 lbs/cu ft converts to ~1 psf per inch depth; wet packed snow at 20 lbs/cu ft converts to ~4 psf per inch. So a foot of fluffy snow = 5 psf, but a foot of wet packed snow = 20 psf.

The calculator also helps you understand when to clear snow off your roof. Most residential roofs are designed for 20-40 psf snow load. When actual load exceeds 75-80% of design capacity (15-32 psf in residential), snow removal becomes prudent. Hire professionals for steep roofs or significant depths — falling from a snow-covered roof is dangerous, and improper removal can damage the roof.

Inputs

Snow Depth (inches)

Snow Density (lbs/cu ft)

Fresh: 3-7, Settled: 10-20, Packed: 20-40, Ice: 50+

Roof Length (ft)

Roof Width (ft)

Roof Pitch (rise/12)

Flat=0, Standard=4-8, Steep=10+

Results

Ground Snow Load

15.0 psf

Roof Snow Load

8.3 psf

Total Weight on Roof

11,125 lbs

5.6 tons

Roof Area

1342 sq ft

Snow Load Reference by Depth & Type (psf)

Snow Depth	Fresh (5 lb/ft3)	Settled (15 lb/ft3)	Packed (30 lb/ft3)
6"	2.5	7.5	15
12"	5	15	30
18"	7.5	22.5	45
24"	10	30	60
36"	15	45	90
48"	20	60	120

Last updated: May 29, 2026

Formula

**Snow load per square foot:** Snow load (psf) = (Snow depth in inches / 12) × Snow density (lbs/cu ft) Snow depth must be inches; density in lbs/cu ft. **Total weight on roof:** Total weight (lbs) = Snow load (psf) × Roof area (sq ft) **Roof area accounting for pitch:** Roof area = Footprint area × Slope factor Where slope factor = √(1 + (rise/12)²) For 6/12 pitch: 1.118 For 12/12 pitch: 1.414 **Worked example: 12 inches of settled snow at 15 lbs/cu ft, on 40 × 30 ft footprint, 6/12 pitch** Snow load: (12/12) × 15 = 15 psf Roof area: 40 × 30 × 1.118 = 1342 sq ft Total weight: 15 × 1342 = 20,130 lbs **Snow density by type:** | Snow type | Density (lbs/cu ft) | Visual | |---|---|---| | Fresh fluffy snow | 3-7 | Very loose, can blow in wind | | Settled snow | 10-20 | Compacted somewhat | | Wet snow | 15-25 | Heavy, sticky | | Packed snow | 20-40 | Dense, hard to shovel | | Old/granular snow | 30-50 | Hard, granular | | Glaze ice | 50-60 | Solid ice layer | | Pure ice | 56-62 | Solid, dense | Density increases with age and moisture content. A foot of fresh snow may compress to 8 inches of settled snow over days. **Snow load per inch of depth:** For different snow densities: | Density (lbs/cu ft) | Snow load per inch (psf) | |---|---| | 5 (fresh) | 0.42 | | 10 | 0.83 | | 15 (settled) | 1.25 | | 20 (wet) | 1.67 | | 30 (packed) | 2.50 | | 50 (ice) | 4.17 | **Building code design loads by region (approximate):** | Region | Ground snow load | |---|---| | Southern US (TX, LA, FL) | 5-10 psf | | Mid-Atlantic | 10-25 psf | | Midwest | 20-40 psf | | New England | 30-50 psf | | Northern US (MN, ND, NY mountains) | 50-80 psf | | Mountain states (Colorado mountains) | 80-150 psf | | Alaska | 50-100+ psf | **Roof snow load is typically less than ground snow load:** Roof snow load = Ground snow load × Reduction factor | Reduction factor | When applies | |---|---| | 0.6-0.7 | Standard residential roof | | 0.7-0.8 | Cold/poorly ventilated attic | | 0.4-0.5 | Heated roof or low pitch in wet snow zone | | Reductions for pitch >30° (6/12+) | Steeper roofs shed snow | So if your ground snow load is 30 psf, design roof load might be 18-21 psf. **Roof failure indicators:** - Visible sagging or bowing in ceilings. - Cracking sounds from the roof or attic. - Doors/windows that suddenly won't close (frame distortion). - Cracks in interior walls. - Roof leaks where there were none before. - Significant snow accumulation on roof (especially after warm-then-freeze cycles). If any of these occur, evacuate the area immediately and contact a roofing professional or structural engineer. **When to remove snow from roof:** - Snow depth exceeds 1 foot on flat or low-slope roofs. - Significant ice dams forming. - Snow load exceeds 50-75% of design capacity. - After warm/cold cycles that create heavy wet snow. - Heavy ice accumulation. - Visible structural concerns (sagging, cracking). **Snow removal methods:** | Method | Pros | Cons | |---|---|---| | Roof rake (from ground) | Safe, DIY | Limited reach (~15 ft) | | Hired professional | Safe, thorough | $200-500+ per visit | | Shovel from roof | DIY removal | Dangerous, can damage shingles | | Calcium chloride socks (ice dams) | Easy DIY | Doesn't remove snow itself | | Heated cables on eaves | Prevents ice dams | Expensive install | **Ice dam prevention:** Ice dams form when roof snow melts (from attic heat) and refreezes at the cold eaves. Prevention: - **Air sealing**: prevent warm air leaks from house to attic. - **Attic ventilation**: keep attic temperature close to outdoor. - **Adequate insulation**: minimum R-49 in cold climates. - **Ice and water shield**: required first 24" of eaves. - **Heated eave cables**: melts a channel for water drainage. **Snow load distribution:** - **Even distribution**: typical for level/low-pitch roofs. - **Drifting**: snow accumulates more on lee side of windbreaks. - **Sliding snow**: piles at edges or below roof valleys. - **Localized heavy zones**: doubles design loads in specific areas. **Code references (US):** - **ASCE 7-22 / 7-16**: Minimum Design Loads for Structures. - **IRC** (International Residential Code): residential snow load requirements. - **IBC** (International Building Code): commercial. - **Local codes**: often stricter than national. **Snow load on different roof types:** | Roof | Snow handling | |---|---| | Steep pitch (>6/12) | Sheds snow well, lower design load | | Standard pitch (4-6/12) | Moderate accumulation | | Low pitch (2-4/12) | Heavy accumulation, full design load | | Flat roof (<2/12) | Maximum accumulation, full design load | | Metal roof | Sheds snow faster than asphalt | | Snow guards | Prevent dangerous sliding snow |

How to use this calculator

Enter current snow depth in inches.
Estimate snow density (5 fresh, 15 settled, 20 wet, 30+ packed).
Enter roof footprint dimensions.
Enter roof pitch (rise per 12" run).
Calculator returns psf snow load and total roof weight.
Compare to local building code design load for safety assessment.

Worked examples

Fresh snowfall during winter

**Scenario:** Just snowed 8 inches of light fluffy snow. 40 × 30 ft footprint, 6/12 pitch. Density ~5 lbs/cu ft. **Calculation:** Snow load: (8/12) × 5 = 3.3 psf. Roof area: 40 × 30 × 1.118 = 1342 sq ft. Total weight: 3.3 × 1342 = 4429 lbs. **Result:** 3.3 psf snow load — well within design capacity (typically 20-40 psf). Total 4400 lbs distributed across roof. Fresh snow is not concerning at this depth; let it settle naturally.

Accumulated wet snow with ice

**Scenario:** February deep winter, 24" of layered snow with ice. Mix of fresh on top, packed underneath. Average density ~25 lbs/cu ft. **Calculation:** Snow load: (24/12) × 25 = 50 psf. For 40 × 30 ft footprint at 6/12 pitch: total weight = 50 × 1342 = 67,100 lbs. **Result:** 50 psf is high — likely at or above many residential design loads. 67,100 lbs of weight on roof. If house is in a region designed for 30-40 psf, this exceeds capacity. Consider professional snow removal. Watch for sagging, cracking, or other distress signs.

Roof rake assessment

**Scenario:** 15 inches of settled snow (density 15) accumulating quickly. Single-story home with 30 × 25 ft footprint, 4/12 pitch. **Calculation:** Snow load: (15/12) × 15 = 18.75 psf. Roof area: 30 × 25 × 1.054 = 791 sq ft. Total weight: 18.75 × 791 = 14,830 lbs. **Result:** 18.75 psf is moderate. Residential roof typically designed for 20-40 psf. Approaching the design load — start clearing or get professional removal. Roof raking the lower 10-15 feet helps reduce immediate stress and prevents ice dams.

When to use this calculator

**Use snow load calculations for:**

- **Winter monitoring**: assessing accumulation against design capacity. - **New construction**: verifying structural design meets code. - **Roof replacement**: confirming new structure can handle local snow. - **Snow load insurance**: documenting condition for claims. - **Engineering analysis**: evaluating existing roof capacity. - **Determining snow removal urgency**: when to act.

**Signs roof is at capacity:**

- Snow depth measurable with ruler at multiple points. - Recent heavy snowfall or extended cold periods. - Ice dams forming at eaves. - Drifting snow piling on certain areas. - Visible deflection in roof structure. - New cracks in walls or doors that won't close.

**Roof types and snow handling:**

**Gable roofs (most common residential):** - Steeper pitch (6/12+): better snow shedding. - Snow slides toward ground naturally. - Lower pitches accumulate more.

**Hip roofs:** - Similar to gable but multi-directional. - Snow distribution often more uniform.

**Shed roofs:** - Single slope, snow slides one direction. - Watch for piling at lower edge.

**Flat roofs:** - Maximum accumulation. - Often have parapet walls that trap snow. - Require regular monitoring.

**Metal roofs:** - Slick surface sheds snow quickly. - Snow guards prevent dangerous sliding.

**Snow drift considerations:**

- **Windward side**: less accumulation. - **Leeward side**: more accumulation; design load multiplied. - **Behind roof obstacles** (HVAC units, chimneys, ridges): higher loads. - **At lower roof sections**: snow from higher roofs can pile up.

**Snow removal best practices:**

**Safe DIY:** - Use roof rake from ground (don't climb). - Remove only 50-70% of snow; leave a base layer to protect shingles. - Remove ice and dense layers first. - Work from edge inward. - Don't use metal tools on shingles.

**When to hire pros:** - Snow depths over 12-18 inches. - Steep roofs (>5/12). - Multi-story homes. - Ice dam removal. - Heavy accumulation requiring rapid response.

**Costs:** - Roof rake: $30-100 (one-time purchase). - Pro snow removal: $200-500 per visit. - Pro ice dam removal: $300-800 per visit.

**Roof retrofit options:**

If roof can't handle current snow loads: - **Add structural support**: gussets, posts, beams under truss connections. - **Replace with truss roof**: stronger than rafter construction. - **Lower pitch**: reduces snow accumulation. - **Steep pitch**: more snow shedding.

**Insurance considerations:**

- Roof damage from snow is usually covered. - Failure to maintain (e.g., not removing snow during prolonged accumulation) may void coverage. - Document snow conditions before and during heavy accumulation. - Photograph any snow load indicators (sagging, etc.).

**Climate change considerations:**

- Snow patterns are shifting. - Some areas seeing heavier, wetter snowfalls. - More rapid melt-freeze cycles create ice dams. - Northern regions seeing later/lighter snow. - Mountain regions: highly variable.

**Engineering reviews:**

For commercial buildings or unusual residential situations: - Professional engineer can analyze actual capacity. - Reviews drawings vs. as-built conditions. - Recommends specific monitoring or remediation. - Required for major modifications or change in use.

Common mistakes to avoid

Underestimating wet snow weight. Wet snow can be 4× heavier than fresh snow.
Ignoring drifting effects. Lee side can have 2-3× the average snow load.
Not monitoring after warm/freeze cycles. These create dangerous ice layers.
Climbing on snow-covered roof. Major fall hazard; use ground-based methods.
Removing ALL snow. Leaving a small layer protects shingles.
Using sharp tools on shingles. Causes damage; use plastic shovels.
Building in snow regions without checking codes. Different regions have very different design loads.

Frequently Asked Questions

Sources & further reading

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