hey all , im in process planning/drawing an 8 by 8 deck for my mom, it will be a freestander resting on girders supported by pier blocks, by question is for the 8x8 size, how many girders should i use?, i keep going back and forth on either 2 or 3 girders. i am planning on using 2x8 for both girders and joists? any reccomendations? also how far in from outer edge of deck should the girders be?
thanks all

 

Handigrguy,
Two beams is fine. The third beam midspan would reduce the size needed for joists. For an 8ft span (your span will be less if you set back the beams from the edge of the deck) with the joists 16" on center 2x6 joists are addequate, but 2x8's will make a more rigid floor. I don't know if the beams should be made of (2) 2x8's or (3) 2x8's. The local building department can tell you for sure or you could just use (3) 2x8's because on a deck that size the extra cost will me minimal. There is no minimum distance from the edge of the deck, I don't remember the maximum (it is a calculation based on the dimensions of the joists and how far they can cantilever). I am sure that it is at least a foot and since the purpose of setting the beams back under the deck is looks, a foot should look fine.
I hope this helps.
Good Luck.