If you are planning a do-it-yourself project, doing plenty of research ahead of time is a wise choice. Deck joist spans vary significantly depending on the amount of wood you will be using. Spans also very depending on the height of your deck. On this site, http://decks-ca.com/Deck_Joist_Spans.html, examples are given using Douglas Fir. As the website says, this is a guide and an engineer
. should be consulted before starting work.
