What size beams do I need for this 10x12 shed foundation?
Question:My 10x12 shed will have a concrete pier foundation. On the piers will set pre treated beams, size undetermined, and on the beams will set 2x8 floor joists. I think 2x6 would work for 10' joists but I'm being paranoid and thinking 2x8.
On the piers I was thinking of using 4x6 beams along the 12' span and tie them together with pre treated 2x6's on the 10' ends. That would mean I'm stacking 2x8 joists on top of 4x6 beams. Does that make any sense? What beams would you recommend?
Answers:
I would put in a total of six piers, three on each 12' run. Then I would build the beam from two 2x8 and use 2x8 joist at 16" OC attaching the joist to the beams using joist hangers. Depending on how high this is above the ground (and if money is no issue) I would use all pressure treated for the frame. If money is an issue use regular framing lumber and maybe put on a clear oil based preservative.
Some have mentioned using 2x6 for the frame. Without knowing where you are located, the species of your local framing lumber, the grade of the lumber and what you are actually putting in the shed, I would stick with 2x8 framing.
8x8
16 inched on center for the joists?
3/4 plywood t & g for flooring?
yo can use 4x4 for beams if you set more pier post closer together
Unless you're planning on some really, really heavy items in your shed, the 2 X 8's and 4 X 6's are seriously overbuilt. For an average shed this size, 4 X 4's and 2 X 6's would be plenty of lumber. I would consider running the floor beams in the 10' direction, though. You'll be amazed how much more that extra 2' of length can cost.
The concrete foundation, you could use 2x4, depends on the width of the foundation. It may take 2X6's which are plates.
usually the floor joists for that size building is 2x8's. You can get the truess precut. Most use 2x4 or 2x6 truess.
If you go to Home Depot or Lowes they have specialist there that can tell you what to use. No use to pay for more than you need. That would be my suggestion. Good Luck
For a shed, your joists don't have to sit on top of the beams (stacked floor system). You just notch out a 1 1/2" x1 1/2" notch out of the bottoms and rest the joist on a cleat (a 2x2, which is really 1 1/2' x 1 1/2"), and toenail the joist to the beam. The dimension of the sill (beam) is more a function of what is attached to it. You don't really need a dimensional beam, at all.
I would use 2x8 joists, with 2x8 rim joists. Rim joists are just 2- 2x8s (in this case) nailed together. They equal the dimension of a single 4x8 sill, but are much stronger and stable than a single timber. I would nail (or screw) a 2x2 cleat on the two sides where the joist ends meet the rim joist. Then I'd notch out the 2x8 joists so that they sit on these cleats, and toenail them to the rim joist (you can also put up one rim joist and nail through it, then apply the second one on top of it).
If the floor is less than 12" from the ground, you'll need pressure terated plywood (which is very expensive). Otherwise, moisture from the dirt is going to rot out the floor. A way around this is to use treated 1x6s. If the shed is going to be a workshop, you can put 1/2" plywood over the 1x6s to close the gaps. If it's for a lawnmower or something, just leave the 1x6s exposed. A workshop means that you will be dropping drill bits, nails, etc, so gaps in the boards are bad.
The reason that you want 2x8 floor joists, is because the joists will sag over a 10' span. In a house, you'd use 2x10s, at least, over a 10' span (that's still pushing it). Generally, I've always limited the span of a 2x10 to 8' or less. (give or take, depending how the math works out). Your best bet is to run the joists along the 12' direction and put a beam (2x8s nailed together) in the center. That will make a 6' span, with the joists resting on the cleats. ALL lumber will sag under its own weight over a long enough span, nevermind the loads that are place on top of it. A treated 2x8 will sag over 10' under its own weight. Over 12', a 2x10 will sag. Just the nature of the beast.
2 x 6 joists at 16 o.c. can have a span of up to 10'-9" without a center support.
So, if you ran the 2 x 6's along your 10' dimension you would only need support under the corners and in the middle of te 12' outside length.
That would only be six supports but just for extra strength I would ad a center support to prevent any sping in the floor.
You should be able to get away with pressure treated 2x6's directly on the piers (if you are looking to save $)
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