Calculating Snow Load

Snow weighs approximately 20 LBS per cubic foot. Or 1.25LBS per inch of depth. Depending on moisture of the snow, it can weigh from 1Lb per cubic foot to over 21LBS per cubic foot.

If the snow on my roof is 20 inches deep that would equate to=20 inch roof snow depth x 1.25 lbs/sq ft= 25LBS per sq ft of roof snow load.

Any ice would have to be added to this formula. Add 5.2lbs for each 1 inch of ice depth.,

Notes to consider- Structures constructed with a building permit are designed for 120lbs/sq ft, older roofs may not meet this minimum roof load.

Until recently manufactured homes were designed for a load of 30lbs/sq ft, check the metal label affixed to the manufactured home to verify your maximum snow load.

Roofs that are made with less than3/12 pitch are a concern as flatter roof pitches hold more moisture.

If we receive excessive rainfall, the weigh of the roof increases quite rapidly.
Please note that there are many dangers when looking to shovel the snow off the roof. You can damage the structure and materials.