Roof Load Analysis

If your roof is flat it is more likely to have snow load problems than if it is pitched.

Roof load analysis.

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. 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. To do this i use conservative too heavy dead loads and full snow loads regardless of pitch. However in my practice i typically use the horizontal run of the roof for both types of load.

Tornadoes special dynamic or hydrodynamic loads etc site specific or case specific data or analysis may be required to determine the design loads on them. Technically you should use the actual rafter length when adding up the weight of roofing materials. The easiest way is to push a yardstick into the snow on the roof selecting an area that looks typical of the overall snow depth. For dead loads you are correct.

Flat roof snow loads p f the snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load. Axial forces from snow loads and roof live loads. This means that one is a fixed node and the other is a rolling node. Roof live loads largest roof loads typically caused by repair and maintenance pitch rise span lr 20 r1r2 12 lr 20 lr horizontal projection roof live load 16 r 1 r 2 live load reduction factors r 1 accounts for size of tributary area of roof column a t r 2 effect of the roof rise.

First figure out how deep the snow is piled up there. A fixed node will provide support in both directions down the length of the roof truss members often called the x and y directions. In order to stay intact and in place a roof must be able to resist loads both permanent and temporary that are pushing. Loads on buildings and structures.

You need to use a snow load formula for flat roofs. In our case let s assume that our structure has a flat roof roof slope 5. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10. 4for walls supporting heavy cladding loads such as brick veneer an analysis of earthquake lateral loads and combined axial loads should be considered.

Step 4 determine the flat roof snow load. Roofs are under a lot of pressure. For ground snow loads greater than 20 pounds per square foot the roof load is equal to. However this load combination rarely governs the design of light frame construction.