The flat roof snow load is calculated using formula 7 3 1.
Roof snow load requirements.
The north zone middle zone and the south zone are identified on the roof load zone map above.
It calls for 20 psf throughout most of ohio and 25 psf along a north south strip in the eastern half of the state.
Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.
The load increases with the use of heavier roofing material.
The minimum design roof snow load after allowed reductions shall be 30 psf.
In areas of the state outside of certified local government jurisdictions the design snow load shall be based on the ground snow loads developed in snow loads for structural design in montana authored by f f.
The final roof design loads shall not be less than 20 psf after all reductions are factored except for lyon storey counties.
In areas where the ground snow load pg exceeds 10 pounds per square foot psf 0 479 kn m 2 the following additional information shall also be provided regardless of whether snow loads govern the design of the roof.
Why snow load information.
The standard practice for a few decades in new hampshire was to build our roofs to support 40 pounds per square foot psf live snow load.
Unfortunately most buildings constructed during those years 1970 2000 do not even meet the 40 psf requirement.
A great deal of confusion currently exists among engineers architects recreation specialists and maintenance personnel concerning the proper snow loading to use for the design and maintenance of trail bridges building roofs and other structures in mountainous high snow load areas.
Schilke civil agricultural engineering montana state university august 1989.
Table r301 2 1 climatic and geographic design criteria ground snow load.
A clay tiled roof may have a dead load.
The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load.
Drift load design in the 30 psf zones may utilize asce 7 16 table c7 1 ground snow values.
In our case let s assume that our structure has a flat roof roof slope 5.
This downward imposed load on the home is also known as the snow load.
Flat roof snow load pf.
The dead load of a typical asphalt shingled wood framed roof is about 15 pounds per square foot.
The north zone design live load equates to 40 pounds per square foot the middle zone equates to 30 pounds per square foot and the south zone equates to 20 pounds per square foot.
Intermediate values may be interpolated by proportion.
The residential code of ohio which applies to one and two family homes shows a map indicating the required snow load.
The 20 psf load is equivalent to 14 inches of snow at the design density while the 25 psf load is 17 inches.
That s about 4 feet of powder and as little as 2 feet of wet snow.
