Figuring Roof Load

Roofs are under a lot of pressure.

Figuring roof load.

This house is identical to our first example except it is stick built. This will amount to twice as much load on the exterior walls compared to a building with a center wall. Load limits on the roof of a building. Explore a number of housing related calculators as well as hundreds of other calculators covering topics such as finance math health fitness and more.

2attic loads may be included in the floor live load but a 10 psf attic load is typically used only to size ceiling joists adequately for access purposes. In order to stay intact and in place a roof must be able to resist loads both permanent and temporary that are pushing. If you live in the us our snow load calculator compares the total weight on your roof with the permissible load calculated according to the standards issued by the american society of civil engineers regarding the minimum design loads for buildings and other structures asce7 16. But isn t it more accurate to figure the weight of snow and roofing materials by measuring along the actual length of the rafter.

If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow. I often see roof loads calculated based on the horizontal run of the roof. Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter. The load on your roof trusses can be calculated based on the number of members and the number of nodes in the structure.

Thus as the roof gets steeper the rafter gets longer and the weight of roofing materials increases. To figure out the load on your roof take the depth of snow in feet and multiply it by the weight of a cubic foot of snow. Unlike the trussed roof live load and dead load of the rafters and ceiling joists must be accounted for as separate systems. For example if building is 24 x 24 and has trusses and the load on the roof will be for 30 lb snow load and a ceiling with no storage will total out like this.

However if the attic is intended for storage the attic live load or some portion should also be considered for the design of. As a result the live load dead load and distribution of forces are different. Sketch out truss structure this step is recommended to give you a better idea of how all the pieces fit together for the type of truss structure you are building. This sizing guide for roof rafters will help determine what you need for your small project.

If the snow weighs 10 pounds per cubic foot and there are 1 5 feet on the roof each square foot of the roof is getting 15 pounds of pressure.