quick question about basement floor construction

hi,
I'm redoing my floor in the basement. Basically on the concrete slab we put a .006 vapor barrier and then the 2x3 on which will be installed 2 layers of 5/8" plywood. The slab is not leveled so basically all the 2x3's are on shingles/shims. We're using tapcon screws through the 2x3 and the shingle into the concrete.
QUESTION: every how many inches/feet are we supposed to support the 2x3 with a shingle and a screw?
(the 2x3 are spaced every 16 inches and on top there will be 2 layers of 5/8 plywood placed "perpendicular" to each other)
thanks in advance
greg
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On Dec 16, 2:33 pm, greg <gstusio[at]hotmail[dot]com> wrote:

.006 vapor barrier and then the 2x3 on which will be installed 2 layers of 5/8" plywood. The slab is not leveled so basically all the 2x3's are on shingles/shims. We're using tapcon screws through the 2x3 and the shingle into the concrete.

Out of respect for the concrete, I'd simply glue the firring strips down, shimmed as necessary. put the vapor barrier on top and screw and/ or glue the plywood down. We tend to be obsessed with mechanical fasteners sometimes when a good adhesive will actually do a better job. Sorry this doesn't answer your question but it seemed like a good time to present a logical alternative to folks who might be planning some similar installations.
Joe
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I need to ask does this basement have any water troubles at all? even the once every 8 years can muck up a newly remodeled basement very bad.
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Oh pshaw, on Sun 16 Dec 2007 07:00:52p, Joe meant to say...

I agree with the glue installation. As far as spacing of the shims, I'm obssessive enough to put a shim anywhere I see a gap.
--
Wayne Boatwright

Date: Dec(XII) 18(XVIII),2007(MMVII)
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On Dec 16, 3:33 pm, greg <gstusio[at]hotmail[dot]com> wrote:

.006 vapor barrier and then the 2x3 on which will be installed 2 layers of 5/8" plywood. The slab is not leveled so basically all the 2x3's are on shingles/shims. We're using tapcon screws through the 2x3 and the shingle into the concrete.

double check your project, it has many answers subject to your climate and soil, incredibly detailed: http://www.buildingscienceconsulting.com/resources/homeowner.htm
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First, don't use spruce or pine construction grade 2 x 3s, a little moisture and they will quickly rot. Use red cedar, redwood or pressure treated rated for basements.
You only need a screw to hold the 2 x 3 where needed, probably about every 4 feet, but will depend on what you require to keep the wood in place without curling. Spacing of the shims can be determined by walking on the 2 x 3s and see how much it bends.
With 16" spacing of the runners, two layers of 5/8 plywood is overkill. One layer is all you need. That vapor barrier really should be on top of the 2 x 3s, if you install it on the concrete it can hold moisture under the plastic sheet as well as on top where it will damage the 2 x 3s. Water will still leak through the screw holes. Vapor barrier on top of the runners will protect the plywood which will otherwise be subject to mould from the damp conditions underneath it.
You may want to install some foam sheeting between the runners for some insulation, however be sure you do not block any waterflow to the drains, as any water that does get in the basement needs to be able to run to the drain.
Screw not nail everything together so that if the worst happens and you have to lift part of the floor, you can do it relatively easy.
"greg" <gstusio[at]hotmail[dot]com> wrote in message

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