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nsobota24 10-02-2012 05:42 PM

Building a shed/building on existing concrete pad
I am planning on putting up a building (10x14) on an existing concrete slab. However the slab is more like a patio, and the building isn't going to be as big as the slab. The plan was to build it directly on the slab and putting in a small overhead door. My concerns are with moisture at the base of the walls, what's the best way to anchor the walls, or if its even a good idea for the fact that there's no foundation under the slab.

I've thought if it is possible to build directly on top of the slab to maybe use 4x6 pt as a base....just an idea

any comments, suggestions, ideas would be greatly appreciated!

GBrackins 10-02-2012 05:56 PM

some questions .......

1. where are you located?
2. do you know if you are required to have a building permit (a shed that size in my area would require one)
3. do you know what your frost depth is? meaning how deep must footings for a foundation go into the ground
4. do you put in the concrete slab? if yes, was top and subsoils removed? if so, what was put in its place?

nsobota24 10-02-2012 06:08 PM

Location : northwest Ohio
Have a building permit already
The concrete pad is already there, I know that the sod that used to be there was removed, not sure how far they dug below that if any but I do know they placed mill run down before pouring concrete not sure how well it was compacted though, this was an extension of an existing patio, and an old shed sat on top this for a few years now (it was a pre built, built on runners) a larger shed/building is desired

nsobota24 10-02-2012 06:09 PM

Frost level I believe is 18", not certain on how deep footers must be though

GBrackins 10-02-2012 06:35 PM

frost depth is the depth that footings must go below grade to prevent frost heave from acting on your building

joecaption 10-02-2012 07:03 PM

Not a great plan to just build it on top of the slab, and yes water will come in under the walls as well as rot out the side since it's so close to the ground.
Sheathing needs to be at least 6" off of grade.
Far better to do as you suggest and build it on the 4 X 6's make sure there's at least three and 4, would be better skids under it to spread the load out.

woodworkbykirk 10-02-2012 08:57 PM

im with joe.. having the sleepers will also encourage air flow underneath which will help keep it dry

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