How to Estimate the Weight of a Porch Roof

The weight of a porch roof is referred to in engineering as "dead" weight. The dead weight of the porch is calculated by configuring how much the materials weigh that make up the porch. This measurement is needed to calculate how much "live" weight the support beams will tolerate. The live weight is rain, snow, ice or any other material that is not permanent. Usually the weight of the materials is not known so a standard weight is usually used for design.

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Instructions

- 1
  Calculate the total number of square feet of the existing porch roof. Use a tape measure to measure the length and the width of the roof. If the roof has a pitch, or goes up in a triangular shape, measure both sides or measure one side and multiply by two. The length times the width gives you square feet.
- 2
  Add any additional areas that do not include the main roof, such as the area above a door.
- 3
  Multiply the total number of square feet by the standard 10 pounds per square foot. This gives you the total weight of the roof. For example, the calculations for a 10 foot by 12 foot roof -- 10 x 12 = 120 square feet. Multiply 120 square feet by 10 psf to get 1,200 pounds.

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