How to Calculate Snow Load for Roof Trusses

Calculating the snow load for roof trusses means taking into consideration a variety of factors, including the load capacity of your trusses, the distance between them, and even the angle of the roof. While these measurements are usually done by an engineer or architect, they can be accurately measured by anybody, usually with the help of a manual or special online calculator. This will allow you to better work together with a professional in determining how to structure your roof, or in determining how much snow your existing roof can hold.

Measuring tape
Calculator

Instructions

- 1
  Determine the slope of your roof, either by using a roof slope calculator (see Resource 1), or by manually calculating the "rise" and "run" of your roof - the amount of vertical rise divided by the amount of horizontal run in the same distance.
- 2
  Determine the actual snow load of your roof with a snow load calculator (see Resource 2). This will require you to know your geographical area's "design ground snow load," which can be found using Resource 3. Once you are finished with the calculations, you will have a snow load figure expressed in pounds per square foot, or "psf."
- 3
  Determine the number of roof trusses and the total area of your roof. You may have to refer to your home's blueprint, or go into the attic with a measuring tape.
- 4
  Divide the square footage of your roof by the number of trusses. Theoretically, each truss supports an equal share of the roof.
- 5
  Multiply the "psf" number that you obtained in Step 2 by the quotient that you obtained in Step 4. This will give the theoretical snow load, in pounds, that each truss can hold.

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