Need help leveling basement floor


I'm putting in a wooden floor over my basement smooth-concrete floor. 6mil plastic, then treated 2x4 sleepers Hilti-nailed to the concrete, then 3/4 osb panels over that. Half the floor is done, and it has gone well so far. I'm adding the floor for insulation purposes, and so that I can use different floor coverings in different rooms.
However, a 20x20 section of the floor slopes down to an unused sump pit. How do I level the floor to compensate for this slope? Do I first nail the 2x4s to the sloping floor (a very slight slope) and then somehow level the osb panels, or do I make the concrete level first before attaching the 2x4s?
And if I level the panels somehow, how do I do it in a way that would prevent the floor from flexing? If the panel doesn't rest securely on the sleepers (for example, if simple shims are used, leaving gaps between the sleeper & panel), the final floor will bounce.
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Darryl wrote:

I had a similar situation once and how I solved it was cut a 2X4 to the desired height from the floor joist above to the top of the sleeper then used that to determine shims and nail length needed to level the floor that would be applied on top of the sleeper. Your example may need wedges cut instead of shims as I don't know what the slope is but use the 2X4 method to see what you need then determine which way to go about it.
Rich
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Neither. Make the two by fours level by adding shims between them and the concrete floor? then add the osb panels as you have on the finished portion.
lee
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For the region where the concrete slab is sloped, I suggest starting with a thicker sleeper (e.g. a 3x4 or non-flat 2x4) and scribing the bottom edge to the floor slope at the proper height to be in plane with the other sleepers. Then you are level and can just attach the osb panels.
To do the scribing, put the sleeper down on the floor, raise up and support one end to make it level, and determine how much higher the top of the sleeper now is than where you want it. Then set a pair of dividers to this amount and scribe the sleeper to the floor. If you cut the sleeper on the scribe line, then it should fit snug against the floor and be level on the top at the proper elevation.
Cheers, Wayne
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http://www.buildingscience.com/resources/mold/Read_This_Before_You_Design_Build_or_Renovate.pdf
http://www.buildingscience.com/resources/basements.htm
Darryl wrote:

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