Psf Roof Load Shed

On a roof with a slope greater than 4 to 12 the live load limit is typically adjusted downward from 20 psf to 15 psf to allow for the relatively greater dead load on the steeper roof.

Psf roof load shed.

For example appendix a indicates that one type of clay tile roof system has a live load value of 20 psf and a dead load value of 15 psf. If there s wall board covered ceiling suspended from the underside of that floor the dead load increases to about 10 pounds per square foot. Technically you should use the actual rafter length when adding up the weight of roofing materials. For roof live loads of 12 psf or 16 psf.

All loads are listed as pounds per square foot of horizontal projection footprint area. Reeds ferry shed floors are designed to carry a live load of 40 50 psf. However in my practice i typically use the horizontal run of the roof for both types of load. The design roof snow load for residential buildings in mn is set by state statutes and is 42 pounds per square foot psf in northern mn and 35 psf in southern mn.

Many factors influence how a system responds to loading. See figure 1 headers. Standard floors use 3 4 exterior grade plywood with double layer and pressure treated plywood optional. Af pa s appendix a lists a variety of live and dead load combinations for floors ceilings and rafters.

For dead loads you are correct. A typical wood frame floor covered with carpet or vinyl flooring has a dead load of about 8 pounds per square foot. For roof live loads less than 20 pounds per square foot psf rafter spans and required e values tabulated for 20 psf shall be permitted to be adjusted in accordance with the fol lowing table. The density of snow and hence its load per square foot depends on the type of snow.

The loads are based on adjusted roof snow loads from the governing building code. However many agricultural buildings are built using a 20 psf snow load which would be expected to handle six feet of dry fluffy snow or one foot of wet heavy snow. On the other hand snow that stayed on your roof for a few days will settle and while it seems that the cover gets thinner its weight doesn t change it s just the density that is different. The dead load on a floor is determined by the materials used in the floor s construction.

Here each square foot of roof system delivers 50 pounds of live load and 15 pounds of dead load 65 psf total to the structural support system. Buildings wider than 8 have a double 2 6 center beam to ensure minimal deflection. For example fresh snow is soft fluffy and light.