Why Roof Snow Weight Matters
Snow looks light when it falls. It can become heavy fast. Wind, thawing, rain, and refreezing change the load. A roof does not feel snow depth only. It feels the mass sitting on each square foot. Wet snow may weigh several times more than dry powder. Ice layers add even more force. This calculator helps estimate that force before removal, inspection, or planning work.
What the Calculator Measures
The tool combines roof area, slope, snow depth, density, ice, rain water, drift load, and safety multipliers. It can also compare a depth based estimate with a design style ground snow load. The final value is shown as pressure and total weight. You also get metric values, line load per rafter, and an estimated load per support.
Important Input Choices
Length and width define the horizontal roof plan. Pitch changes the surface area, but vertical roof load is usually applied to the projected plan area. Snow depth should be measured in several places. Density should match the snow condition. Fresh snow is often light. Settled snow is heavier. Wet snow is much heavier. Ice should be entered separately because it is dense.
Interpreting the Result
The calculated load is an estimate, not a structural approval. A low number may still be unsafe on damaged, old, poorly braced, or flat roofs. A high number deserves attention. Compare the result with local code values, truss drawings, or advice from a qualified engineer. Do not walk on a weak roof to measure snow.
Safe Use
Use this calculator as an early warning tool. Check gutters, valleys, dormers, low slopes, and drift zones first. Remove snow evenly when possible. Avoid creating unbalanced piles. Watch for sagging, cracking sounds, stuck doors, leaks, and ceiling movement. These signs need urgent care. For large buildings, hire trained crews and request a structural review.
When to Recalculate
Recalculate after heavy wind, freezing rain, or a warm spell. These events can raise density without increasing depth. Enter a higher drift surcharge near parapets and roof steps. Recheck after partial clearing, because remaining snow may become uneven. Keep each saved result with the date, location, and measured conditions for later comparison. This record supports better winter decisions.