Build on this existing slab?

[jimy]

My wife and I are looking at some property that has a slab about 34x34. It is probably 10+ years old. Looks to have been poured in 4 sections (or perhaps has the "lines" scribed to induce nice straight cracks). It measured 5 inches thick at the edge in the handful of spots I checked. Looks to be in great condition although the surface is somewhat rough. Seems flat from a causal glance. It has gravel around the perimeter and seems like under the slab as well.

Does it seem likely I could build a garage on this? Is 5 inches thick enough at the edges to connect the bottom plates of a stick built garage?

thanks,

Jim

 

[Red 17]

You could excavate around it and pour a proper footing and stem wall. Serving suggestion.

 

[readhead]

Don't know where you are but my initial response would be no. As suggested a footing and stem wall could be installed.

 

[rsanter]

You could excavate around it and pour a proper footing and stem wall. Serving suggestion.

This is how I would approach it

 

[jimy]

Thanks - this is in upstate NY. So would that proper footing be something below the frost line?

 

[readhead]

Probably but the best thing would be to ask your building department, if there is one involved.

 

[Voi]

It has been suggested in these threads before that a post frame structure could be built around an existing slab.

If the ability to build on or around this slab has any bearing on your possible offer I'd at least check to see if it's square, level/flat, etc.

 

[ManOnTheCouch]

Mine was built on a 6” slab like that. It’s 30x60, 12’ walls and 2x6 construction. I’m in KS and many outbuildings are frequently done this way on a slab. May be different in other parts of the country depending on soil or base that the slab is on as well as weather. Your best bet is to find out what the local standard is.

 

[ConCretin]

I'd feel a little more comfortable if there was a thickened haunch around the perimeter to provide a little more support for the walls and to hold everything together but I don't see any reason you can't put a wood structure on it. The loads imposed by a wood structure are pretty minimal.

IMHO excavating around and under it to add additional foundations would be costly and is as likely to create problems as it is to solve them.

 

[Kaizen]

I'm guessing no you cannot build on it. I seriously doubt that is 5 inches thick in the middle. Looks like it was intended to hold patio chairs. I also doubt that the soil was prepared in such a way to make an alaskan slab doable even if you do pour a thickened edge. pole barn might be a great idea if it fits with the look. also remember you need a lot of driveway to get there. sorry.

 

[rayra]

Thanks - this is in upstate NY. So would that proper footing be something below the frost line?

yes, properly and for longevity.

It should be possible to readily excavate around its perimeter and under its edge and basically pour or proper depth footing and support and stem wall to turn that into a floating slab, supported at its edges. And then with the stem wall in place very easy to build whatever structure you want on it.

Here in SoCal garage slabs on grade are not really any thicker than what you seem to have. A few 1/4" dia holes drilled in your slab semi-randomly placed from the center to the edge will let you gauge the thickness of the slab with a coat hanger with the tip bent 90deg. you can stick it down the hole and feel the bottom.


eta if you want to determine the true nature of your slab, it would be fairly easy to dig a small narrow trench perpendicular to your slab and in under it, so you can determine what the shape of the slab is and what is really underneath it.
Bonus - if you intend to build on it, figure out where any utility entry would be and put your trench there where it'll be needed later anyway.

 

[jimy]

Thanks for all the good info. I'm good for now, we are still deciding whether to make an offer on the property or not. In any case, the slab seems a plus regardless of what we might do with it. And given that it has held up well over a number of years is a fairly good sign.

Jim

 

[Jinks]

Use the need to remove it as a bargaining point for a lower bid. After you get the property drill a small hole to verify the thickness at the center (or other points). Once you own the property you can decide if it's worth the cost of removal, the cost of a footer, or solid enough for a garage, a shed, a parking pad, a pool/sun deck, or any other thing you might want.

 

[Bluedodge]

if nothing else, you have a nice place to pop up a basketball hoop for the kids.

 

[woodzy]

I purchased the lot next to my house and there was a garage with a large slab in front of it. It is really nice to have a slab of concrete for things like splitting logs, parking cars, trailer, or just about anything else you want to do on a flat area. You don't need to water it, cut it, treat it. This slab is not in great shape but I would not get rid of it. So, if you were to buy this property, just build the building right on the edge of the current slab and you will have a very nice approach.

As you can see the truck is parked on the slab in the far left.

View media item 95063

 

[Bretny]

34x34 would cost roughly $3500 in forums, rebar and concrete if you do the work yourself. A flat pad like that with nothing around it is prob the easiest concrete job you can do. Is $3500 worth the risk of what ever your going to build on it?