Roof Load Analysis

I often see roof loads calculated based on the horizontal run of the roof.

Roof load analysis.

For ground snow loads greater than 20 pounds per square foot the roof load is equal to 70 of the product of the exposure thermal and importance factors the ground snow load and 20 pounds. It is important to list live load dead load and total load separately because live load is used to compute stiffness and total load is used to calculate strength. You can enter these values in any units you d like including meters and feet. It is a good idea to fill in the resulting numbers from the truss load calculations on your roof truss sketch from the beginning.

But isn t it more accurate to figure the weight of snow and roofing materials by measuring along the actual length of the rafter. Alternately there are now computer software programs that will both calculate your roof truss load and render a diagram of what the end result should be. Thus as the roof gets steeper the rafter gets longer and the weight of roofing materials increases. Create a truss load diagram.

To calculate the weight of snow on a roof use the first two sections of our snow load calculator. This will help you keep track of them while installing each triangular truss and it can be a handy reference for which nodes you have assigned as load bearing fixed and rolling. Length and width of your roof. You need to supply the following information.

If your roof is pitched enter the length and width of the flat area covered by the roof. Roof load live load design is affected by the shape of the roof whether it is flat curved or pitched. For roofs that are flat and with ground snow loads lower than 20 pounds per square foot the roof snow load is equal to 70 of the product of the exposure thermal and importance factors and the ground snow load. Roof loads are a downward vertical force on the home.

This downward imposed load on the home is also known as the snow load. The north zone middle zone and the south zone are identified on the roof load zone map above.