# Adding a Shed to an Existing Concrete Slab



## agrichick45 (Apr 14, 2014)

I just bought a house (0.5 acres) enough for me to start a decent homestead, without bending to the rights of the landlords. 

There are no sheds or outbuildings, and I need a wood working workshop. There is a concrete slab out back (25 x 25 or so). How difficult is it to use this existing slab to put up a 10x12 or 12 x 16 foot shed onto the current site? The slab has some minor cracks in it, but seems to be in pretty good shape otherwise. I believe it was used as a basketball court or porch in a previous life. 

Thanks


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## jwal10 (Jun 5, 2010)

Probably no wire, rebar or footing. Depending on thickness it may work if you center the shed width wise on the slab and set it forward the same distance from the back, it might hold a shed. Put down a treated bottom plate on the slab, build and stand up the walls, attach the double plate to the slab with anchor bolts. If any water stands on the slab anywhere it might seep or blow under the treated bottom plate. You could use construction adhesive between the treated plate and concrete....James


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## agrichick45 (Apr 14, 2014)

I agree that the footings or rebar are probably missing.

Instead of placing directly on a foundation, I could use some girters to raise up the level of the shed as well? Since the slab is flat, I wouldn't need the use of gravel. That way, the shed can be up off the ground a bit?

Or, I could preserve this patio for something else, and put up a shed elsewhere.


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## Guest (Jul 18, 2014)

Get a hammer drill(a good one, and a 6" long bit. That way, you can drill into the slab and find out how deep it is. If you put floor joists directly on the slab, you might want to use some sort of clip with masonry anchors. I've had a 12x24 bulding sitting on cinder blocks for 9 years, no shifting or anything, and the back corner is 3 ft above grade. In this county(and many other counties in NC), you can build a farm building/storage shed up to 12x12 without a permit or inspection.


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## agrichick45 (Apr 14, 2014)

Here, we need a zoning permit for everything, including a fence. But I wanted the roof to overhang in front, so roof will be 12x16.

If the slab s deep enough (4+ inches), I can use it for something smaller with brackets and screws

thanks


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## wy_white_wolf (Oct 14, 2004)

One thing to worry about when putting a small building on a large slab is drainage. The concrete will pool water around a the shed so it ends up sitting in it every time it rains. Causes the sills and lower part of the walls to rot faster.

WWW


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## agrichick45 (Apr 14, 2014)

I study urban stormwater design, and could come up with some creative solutions to minimize this problem. But I agree with you.


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## MO_cows (Aug 14, 2010)

Why not build with pole barn style construction, around the slab? Then your structure is anchored into the ground, the slab becomes the floor.


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## agrichick45 (Apr 14, 2014)

MO_cows said:


> Why not build with pole barn style construction, around the slab? Then your structure is anchored into the ground, the slab becomes the floor.


I don't know if our budget will allow it...


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