Roof Deck Live Load

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.

Roof deck live load.

The live load that a structure is required to resist varies and is based on similar criteria as the occupant load table 1607 1. 1 for garages restricted to vehicles accommodating not more than nine passengers 3 000 pounds acting on an area of 4 5 inches by 4 5 inches. 2 for mechanical parking structures without slab or deck which are used for storing passenger vehicles only 2 250 pounds per wheel. The load that is placed on your deck is expressed in pounds per square foot psf and the total load or more appropriately the design load is comprised of the dead load and the live load.

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. 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. Conventional deck construction can support greater live loads by using larger dimension lumber or closer spacing of joists and beams. For assembly uses such as restaurants churches and music venues the minimum live load is 100 psf.

Occupant load of 50 or more. Dead load is basically the load created by the weight of the deck itself. 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. 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 example a restaurant deck without fixed seats must be designed to resist 100 psf while a deck serving an office must resist 50 psf.