Need Help Lifting & Putting Floor Under a Shed

[Bunk]

Hey Everybody-
I need some help figuring out the best way to fix this situation with my Son's shed. He has a newly built 10'x12' shed his FIL helped him build. The trouble is they didn't fully think things through and they just built up the walls on the concrete slab next to his home without being concerned about being level (the slab is off ~1-2" over 10') or more importantly putting a platform floor underneath the thing to keep all his stuff dry on the inside and the sheathing from rotting.

At least the base plate is treated 2x6, walls are 2x4 - 16" oc. It isn't 100% completed yet because of cash flow issues, but right now he has it sheathed and wrapped, but no siding, and tar paper on the roof.

He needs to store a motorcycle inside, wants a workbench and a couple heavy duty shelf units. I am thinking he needs a 2x6 floor with 3/4 T&G. How tight should the joist spacing be?

I see we have a few options in getting a floor in and the structure out of the wet:
1) Leave the structure on the slab and build the floor inside the structure
2) Somehow lift up the structure enough a slide under a proper floor. Maybe using concrete post support piers?

Definitely a case of doing it right the first time being way easier than fixing it after the fact.

Anybody have some advice?

 

[holt2ton]

Is the top plate level? I mean did they account for the slab being un-level and cut the wall studs to make the top plate level? Or is the whole shed tipped the same as the slab? It's a shed...is he really concerned about it? If the shed is level then wall units and benches can be mounted level regardless of the floor. If I was that far into the project already I would probably lay down some heavy weight plastic and lay PT plywood down and secure it with some flathead Tapcon screws.

 

[kd3pc]

my garage floor is concrete and the walls are built on a plate that sits on that concrete....no "platform floor" as have every one I ever owned.

Just what is it that makes you think this shed is lacking....??

 

[TractorJeff]

Do some landscaping around the shed to keep water off the concrete floor/pad is the simplest solution!

 

[Bunk]

The walls were built on the ground and lifted up into place, so the top plate/whole shed is tipped same as the slab.
Honestly, my real concern is really the wetness. After it rained yesterday there was some standing water on the slab. I'm afraid the sheathing is going to **** up the water and snow melt. Admittedly these are my concerns I am voicing, but he wants to have tools and stuff in there and I have had bad experiences in the past with stuff getting rusted up inside damp/wet old garages, as well as rotten framing from wetness. I don't want him to be sorely disappointed next spring, you know?

 

[Falcon67]

My shop is off 6" NW to SE across the 40' dimension and 6~8" out of square. It's not a big deal.

As for moisture, that depends on how far the slap is above grade. I've had a shop (20x24) that was literally "on grade" because the contractor didn't do as requested and I had to be somewhere across the country. What I did to prevent water infiltration was to trench the perimeter about 6x6 and fill with gravel, then use 12" flashing across the floor plate and slab joint, then cover with the siding. That building is having it's 20th anniversary.

 

[Bunk]

@kd3pc - Yeah when you put it that way, there is definitely some sense in that. The trouble is the tilted slab with standing water and that the bottom plate isn't bolted or sealed down. To be clear - it got built in a puddle.

@Falcon67 - The slab it was built on is part of a much larger slab that the manufactured/trailer home sits on. So it is at grade. No chance of trenching around like you mentioned.

 

[Bunk]

Here is a pic from early in the build. It has since been moved further away from the house. They built it closer than code allowed, but that's another story.
View media item 72665

 

[tjdux]

Is the slab below grade?

Also is it a full slab or concrete stem walls and dirt floor? If itbis full slab why do you need something beyond a concrete floor?

Is it a shed built on what im guessing is a concrete patio that already exhisted? Some photos would be helpful i feel.

1 to 2 inches over 10 feet is less than .25 inch slope per foot so thats not terrible for a garden shed sized work shop. My 24x36 shop doesn't have perfectly level floors either (i didn't build it).

That little of slope may be better fixed internally by shimming shelf legs and its certainly not gonna bother a motorcycle any.

As far as keeping water out... this is where photos really would help. Whats the water run off situation here? Are gutters the answer?

One thing for sure would be sealing the sill plate to the concrete on the high side so water doesn't flow under it. They make specific water proof sill plate tapes that will do a great job of this. Search google or amazon for sill plate tape or sealer tape. I don't remember any good brands or specific products off the top of my head, sorry.

For the sheathing... cut off .25 inch from the bottom so its not actually setting right on the ground would be my reccomendation. Or it may be easier to remove and redo the sheathing and use a thin removable shim when installing to keep it just off the ground.

Sure it may get wet during heavy rains but it will dry. Or put the whole building on a double sill plate so its 1.5 inches off the ground.

Either way just let the siding hang down a smidge and you will never really see it or paint the bottom to match.

Good luck.

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[Squashfest81]

That's a little structure. Jack a side and slip in a piece of plastic trim/decking gooped in construction adhesive. Then move to the next side.
That's what I'd do.

 

[Falcon67]

Get some 4x6 PT runners and put under it.

 

[gungatim]

PT 4x4's is what I would add under it to raise it. my small shed sits on a slab I poured at ground level and had the same issue. sill seal and/or caulk should keep it dry, but it looks like you are going to get water from the trailer roof dripping as well as the shed roof. need to deal with that somehow, gutters maybe?

 

[Shiftless]

to that ^^^^^^^^^

Install gutters on the mobile home.
Build a PT plywood floor supported by PT 4x4s.

Depending on how much more work has been done, it might be easier to start over again salvaging as much as you can.

 

[TractorJeff]

Yeah, you can't leave that at slab level! No amount of "GOOP" will keep that concrete to wood sealed from trailer roof run-off! And snow load from the trailer!
Build a 2 by 4 frame with 16" centers on top of a couple of 4 by 4's using 3/4" plywood for the floor. That should hold a motorcycle and some tools!

 

[kbs2244]

Gutters are the answer for sure.
Both buildings.

 

[tjdux]

Is this their forever home? I wouldn't worry to much about that little shed. Now that ive seen the photo its gonna take a lot to keep the runoff from that trailer away from the shed base.

The plastic trim under would be a solid way to to keep it dryer but keeping 100% of the water out may be a futile effort. Still lots of silicone or sill sealer will slow it down for awhile.

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[DGersic]

That doesn't look very big. Build the floor you want under it, get a couple of friends over, pick it up, and put it on the floor. Some 4" screws should hold the base to the floor and you're good to go.


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[nickelmore]

Pry bar, floor jack, and as others have said 4 x 4 treated on 16 inch centers.

 

[PoorOwner]

You are missing this, plus a plywood or OSB floor.

You just need to level the runners, makes it easier.

I'm not sure if you are going to have siding or is that OSB sheathing is going to be the outside finish, I would look into having smart side and cover the plywood edge.

 

[Evilunclegrimace]

Build a proper deck like PoorOwner showed, screw some 2x4 lifting cleats to the out side and have six guys pick it up and set it on the new deck. Screw it down and slide into place, level it with some PT shims and you will be GTG.

 

[Bunk]

Thanks for all the help guys. You all helped confirm I wasn't crazy about it needing to be lifted up off the slab. I believe I have a plan now, all we need is time.

 

[The Tool Tyrant]

Or...use three 4" diameter pipes under the bottom plate and roll it off the slab. then form a raised 3.5" slab on top of the existing slab. Drill into the existing slab and epoxy a few short pieces of #5 rebar to tie the two slabs together. Of course this is a more costly way to go but once it's done, there's no worry about water intrusion or rotted wood.
That works out to roughly 1.3 cu. yd's of concrete.

 

[CJ7VFR]

Build a proper deck like PoorOwner showed, screw some 2x4 lifting cleats to the out side and have six guys pick it up and set it on the new deck. Screw it down and slide into place, level it with some PT shims and you will be GTG.

That sounds like a good idea. Some beer and pizza and you got yourself a lifting party!

Jim

 

[dave*99]

Looking at the photo, I see the sheathing does not cover the last stud on the end of the walls. That means it would be easy to cut the nails holding the corners of the building together and separate the 4 walls. If you are more comfortable doing that than lifting or rolling the structure out of the way to build a floor deck, either way will work.

Sheathing should cover those corners though.

 

[Bunk]

@dave*99 - true, at the time the photo was taken, but now the roof is on and the thing is wrapped. I really wish I could have managed this project for him instead of his "Contractor" FIL.

Can't make any mods to the slab, they are just renting the site. Own the home though. At least that's my understanding of how it works.