Occupant load of 50 or more.
Roof deck live load.
Floors in garages or portions of buildings used for the storage of motor vehicles shall be designed for the uniformly distributed live loads of table 1607 1 or the following concentrated loads.
Roof decks with roof coverings in general occupied roof space with structure above is used for assembly occupancy a 2 and will be considered a story per the definition of a story see above.
One shortcoming of the span tables in the international residential code and the american wood council s prescriptive residential wood deck construction guide dca 6 is that they re limited to decks with a live load of 40 psf and a dead load of 10 psf.
Dead load is basically the load created by the weight of the deck itself.
Considering a roof deck as a story may be acceptable when the height of the deck does not exceed 2 3 stories depending on the construction type and.
Conventional deck construction can support greater live loads by using larger dimension lumber or closer spacing of joists and beams.
The live load that a structure is required to resist varies and is based on similar criteria as the occupant load table 1607 1.
For example a restaurant deck without fixed seats must be designed to resist 100 psf while a deck serving an office must resist 50 psf.
This is usually about 10 psf.
For residential decks designed for entertaining large groups it s not a bad idea to overbuild it from the minimum 40 psf required by building codes.
You can design your deck for a soil load with a maximum of 1 250 psf pounds per square foot as it is unlikely that any clay soil would have less than 1 250 psf capacity or you can contract with a soil engineer to obtain the exact psf rating of your soil and your local municipal building department may be able to provide you with some soil load guidelines for your area.
For assembly uses such as restaurants churches and music venues the minimum live load is 100 psf.
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.
