Originally Posted by screasy
I am reading this post with much interest. I am building a coop that is 16 X 12 to accomodate up to 50 chickens. They will have access to an outside run. The main question is about the floor. I have decided to elevate the floor, and now I need to decide on the joists and how to attach it to the ground.
I have about decided to go with 4X4's resing on concrete deck piers with 2x6 joists. The question is for a 12' span, can I use 2' on center for the joists, and how many piers should I use? What about piers in the middle?
If you use piers in the middle then you'd be making a beam those piers would support and have two spans for joists. If that's your want then go ahead but it's easy to get 12' lumber so why not just have a 12ft span. Use 2x8's graded structural or No 1 and spacing of 2ft. I'd use joist hangers for best connection and wouldn't even hesitate with 1/2" plywood screwed down. There will be deflection when you walk on it but that's outbuilding construction. If you want the floor residential code- no deflection then space it 16" on center.
2ft on center spanning 12' will carry over 30lbs per square foot (now don't think that it's only 30lbs rather that weight over the entire floor as in you could put 30lbs every square foot and floor would easily hold it-3 tons spread out) so some spring when large person walking. 16" on center with select grade is 60lbs per square foot load- over residential and no deflection whatsoever.
Forgot about your piers. I'd just do 6, 3 piers along each 16' end. That's what is carrying the load of the joists. As you'll never be carrying 3 tons in it, just double up 2x10 (I'd use the 10") or 2x12's for the two beams. With 4- 8 footers per beam you'd cut one 4' so the beam has a joint overlap of 4' and nail or screw the boards together. The end boards of your joists you'd keep same depth as the beam just for construction purpose so a 12' 2x10 or 2x12 nailed onto the two beams to complete the square.
I never know if I'm being clear...so will quickly recap. a 16' beam (2-2x10 wide nailed together- 4',8',4' nailed to 8',8') on each end over three piers each, two 12' boards same depth as beams to complete the outer floor framing. That leaves 7- 12' 2x8's spaced 2ft on center with joist hangers (14) to connect to the beams. Yes, the piers can be pressure treated 4x4's right out of the ground from frost depth or use 8" sonotubes and put bag cement in, devolop around the 4x4's last 12" of sonotube.
Edited by Egghead_Jr - 11/5/15 at 9:19am