50 lbs per sq foot - Structural Standards
40 lbs of dead load and 10 lbs of live load. Every deck builder should know these figures because they part of the International Residential Code for building decks. From our experience, lack of code compliance accounts for 90% of the deck failures we see when the deck has not exceeded its expected lifespan. Most likely because the builder did not have a permit, or else a municipal inspector would have most likely picked up the problem at the time of construction. Structural errors account for about 50% of the problems we can identify. If your deck is 20 years old, it is likely that it does not meet the current standards. However, Simpson, a manufacturer of deck hardware has a great comprehensive deck guide that helps builders retrofit older structures so they are compliant.
When designing a new deck, we pay close attention to the foundation loads, beam spans and joist spans. The international residential code table R507.5 is a great resource for identifying the proper span for some of these members, the rest is simple math. However, no document is more consulted in our office than the prospective deck guide published by the American Wood Council. The document fits into the residential code and is well laid out and understandable. When qualifying your contractor ask why kind of standards they follow and make sure they make mention of these documents. You will really start to see the difference between builders concerned with construction of quality structures and those who are just winging it.
Feel free to call OnDeck experts 866-278-2842 with questions any time. Happy and safe deck installing!