Roof Load Analysis

The north zone middle zone and the south zone are identified on the roof load zone map above.

Roof load analysis.

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. You need to supply the following information. 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.

I often see roof loads calculated based on the horizontal run of the roof. 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. If your roof is pitched enter the length and width of the flat area covered by the roof. Length and width of your roof.

Thus as the roof gets steeper the rafter gets longer and the weight of roofing materials increases. 50 psf x 14ft 700 pounds per lineal foot. 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. This downward imposed load on the home is also known as the snow load.

To calculate the weight of snow on a roof use the first two sections of our snow load calculator. 910 pounds per lineal foot. 15 psf x 14ft 210 pounds per lineal foot. Roof loads are a downward vertical force on the home.

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.