flooring uneven basement

I am redoing my basement (see my other posts :) ), and I am considering flooring. We have a cement floor, which is not perfectly level (it goes up a bit near the walls for example, and I think there's some dips and valleys in the middle, which aren't all that visible right now, but I bet would be if I put laminate down.
I'm putting some sort of subflooring down, but I don't know of any that would help with this. I'm wondering if anyone has any ideas about this?
John
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There is a difference between flat and level. What you describe is a floor that isn't flat :)
Semantics aside, how severe are these irregularities in your floor? With a traditional subfloor (sleepers + plywood/OSB), you can shim the sleepers to be level. Grind down any high spots in the concrete.
In my basement, we used pre-made 2'x2' OSB panels with a layer of XPS insulation. They are only 1.25" thick, which saves some headroom. You can buy little plastic shims to level the subfloor while installing. It is a floating floor which somewhat limits floor covering options (laminate is ok). For your situation, you could trim the insulation to allow the panels to fit around the uneven perimeter. The product (OVRX Barricade) may not be available in your area.
Alternately, you could just put some heavy/industrial carpet down. That would at least be able to conform to undulations in the floor.
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On 10/25/2010 11:58 AM, John wrote:

There are a number of self leveling compounds you can use that are cement based. They are designed for cement floors.
Laminate clicks together, if the floor is hilly it will be hard to get them to snap together (the previous row will be bowed). Take a straight edge and get a feel for how uneven the floor is. 1/4" over 3' should be OK.

I would think the subfloor would take care of everything, and give you chance to insulate under.
Jeff
I'm wondering if anyone has any ideas

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Have you priced a terrazzo floor? Definitely unusual, but considering the longevity, appearance, and being absolutely level, it might be worth it to you. With construction in the doldrums these days, terrazzo firms in some areas might be worth looking at.
Joe
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On Mon, 25 Oct 2010 08:58:18 -0700, John wrote:

How much height do you have to work with? I've got just enough in mine to lay 2x4" joists and shim them out to make things level, with 3/4" ply over the top of that. I'll probably run joists on 12" centers and shim every 2' or so to minimize flex. I think I'll end up with about 7' 6" of height (once I've got some covering down and 1/4" ply on the ceiling), which is workable given that it'll still be utility space, playroom for the kids etc.
On that kind of spacing you could, possibly, even turn the 2x4"s on their sides - they'd be bendy as all hell, but with 12" spacing and lots of shims maybe it wouldn't matter.
My basement floor gets pretty cold, so the 2x4"s give enough height to put some insulation in too (although I keep wondering about under-floor heating, but I'm not sure how much benefit it'd be to the main living areas on the floors above, and it's possibly a waste to directly heat space that isn't used that often)
cheers
Jules
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