basement subfloor support


Old 09-01-15, 11:23 AM
Thread Starter
Join Date: Sep 2014
Posts: 7
basement subfloor support

Hi all,

I am trying to figure out how to install my subfloor in the very uneven basement slab I have.
* The slab has up to 3in level differecence in some areas.
* the ceiling height is critical, so I have to keep the sub-floor structure as low profile as possible.

See attached image. What option would be best?
Filling with cement under each 2x3, or adding shims every 12 in under the 2x3?

If filling with cement, do I need to drill the slab and add metal rods to keep the new cement from moving on top of the slab?

Thanks for your help

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Old 09-01-15, 11:30 AM
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Join Date: Oct 2004
Location: WI/MN
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I'd level the concrete and skip the 2x3s.
Old 09-01-15, 01:36 PM
Join Date: Jan 2011
Location: USA
Posts: 4,183
What's the plans for the finished floor?
Almost never a good idea to add a sub floor over a slab.
Old 09-01-15, 06:39 PM
Thread Starter
Join Date: Sep 2014
Posts: 7
Hi joecaption,

Why is it not a good idea?

I plan on putting a plastic membrane over the concrete to keep the humidity out, and then just lay the subfloor on top.

@Stickshift: I can't level the whole thing with cement. Need to keep the slope for any eventual water infiltration that might happen. It all slopes towards a drain.

I did have a french drain installed this summer, so there shouldn't be any more water comming in, but, better safe than sorry. Also leveling the whole basement with cement would be a hell lot of cement to level!

Please keep your comments coming! Maybe I<ll learn something.



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