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Help with building a wooden foundation for new shed

6K views 9 replies 5 participants last post by  iliketowork 
#1 ·
I just bought a shed this weekend, a good metal shed thats 8'x10'.

The land its going on is uneven so i bought 2 x 10' 4x4s as the base.
I then have 8' and 10' 2x4s to do most of the base framing.

My concern is how to get the 4x4s in the ground and make a perfectly level base. i have a post level to make sure that the posts perfect up and down, but not sure how to measure out the length of the posts.

I was thinking about building the 8 x 10 base and setting up the postings and continually correcting the height of the posts until all is level.

any suggestions would be fantastic.
 
#2 ·
Not sure if I'm following, but sounds like you want to bury the 4x4's vertically in the ground, then attach the framing for the floor to them. If that's the plan, just bury the posts, leave a little extra above ground, and then use a laser level to mark each post. Once marked, cut the posts off and all should be level.

If you don't have a laser level, mark one post, then use a straight 2x4 and a level to mark the other posts. (Make sure to do a diagnal check for level also just for assurance). After marking all posts, and rechecking, cut them at the marks and all should be level.

If that's not the plan (burying the 4x4's verticaly and attaching floor framing to them), a little more detailed explanation would help.
 
#3 ·
that is exactly the plan.

i want to have four vertical posts and attach the 8' beam and 10' beams to them.

the laser level sounds like it will simplify everything alot.
here is another dumb question, should i attach the 8' and 10' beams to the side of the 4x4 post or on top of it?
 
#4 ·
OK, now you've lost me; you're putting beams under your shed floor? Or are you talking about the rim joists (4 outside boards that go around your floor that your floor joists attach to) for the floor framing?

FYI, I personally would use more than 2x4's for the floor joists. 2x6 minimum (2x4's are only 3.5" wide and the floor would probably have some bounce to it). Also, I'd use only pressure treated wood (much more resistant to moisture and rot, especially with the humidity that can collect under a shed floor.
 
#5 ·
does this help?

in the top imagine the black lines are the 8' and 10' beams, the red are the posts and the blue are the stringers that i plan on running

which design should i follow?

also, i will remeasure when i get home. i think they are 2x4s, but could be 2x6's

 
#6 · (Edited)
Definitely go with the first one (posts at the corners) -- the wider the stance, the more stable it will likely be. You can lag/carriage bolt the ends of both the 8' and 10' rim joists to the post. (wouldn't recommend just screwing/nailing them since they are carrying the load of the shed to the posts). Make sure to use 2 bolts on each end of the rim joists (2x6 lumber also gives you more width to use 2 bolts on each end).

Did you get pressure treated lumber? If it is 2x4 lumber, you may want to see if you can exchange it for 2x6's.

If your lumber is pressure treated, make sure to get nails, screws that are compatible with the pressure treatment (ACQ is most likely used for anything under 2x8-- so get ACQ approved screws/nails). If you use ordinary screws/lumber, the ACQ will eat them up quite quickly.
 
#7 ·
Four 4x4s don't sound large enough to carry the weight of a loaded 8' x 10' shed. I think I'd go with 6 of them to break up the floor load midway (I'm no engineer however).
Also, I'd use some sort of Simpson metal connection on the post top to carry the floor joists. This will improve stability and provide uplift protection required by some municipalities. Do you need a building permit? Have you checked on set-backs and other requirements before doing the work?
 
#8 ·
i am starting to think that 4 might not be enough. not sure how much weight will be in the shed but at least a few hundred pounds with the mower, mulch and other items.

the wood is treasure treated, but they are 2x4s.
i will definately look into the lag/carriage bolt
 
#9 ·
Baffled as to why you would go with a timber floor construction for an outside shed. Surely, you would have considered a 4 "concrete slab laid on 2" sand as a much better alternative. Possibly cheaper and easier to do as well. If you must go with timber, your beam sizes won't span 10'-0" without serious bending. You need at least 2" x 10" minimum, 2"x12" better to span the 10'=0" direction. Two extra posts midway would reduce this requirement to 2"x6" as stated in previous post and your span is now 5'-0". The same applies to your 8'-0" span, bigger joists 2"x8" or two more posts to reduce spans down to 4'-0". Carefull placement of posts however will allow you to get away with only three extra posts, aligned with the 8'-0" span and in the middle of the 10'-0". A 3/4 plywood deck would form the floor. All timber in the ground or exposed to weather should be preservative treated.:whistling2:
 
#10 ·
Before we had laser levels

One old trick, before we ever had laser levels is to use a string level. They are less than $5.00. If you are working alone you put a nail in one of the 4 x 4's then run the string to the other 4 x 4. Just fasten it anyway for now (I used 3 penny nails so I could just jam it in temporarily. Then hang your string level on the string and go back to the second 4 x 4 and move the string up and down till level. I built many fences this way and still use the string level.
 
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