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Old 02-14-2009, 12:46 PM   #1
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Wood subfloor with slab room addition

Had a room addition added to my raised foundation house. As you can guess the slab is off by 1/8 inch lower where the two floors meet to form one large room. It actually starts off on the same plain then slowly drops down 1/8 inch over a four foot distance. This my sound picky, but every time I walk over this it bothers me. I have used floor lever liquid before, but the surface tension of the liquid is higher than the problem. I will be putting Lazon engineered flooring over the hole room. Better Ideas?


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Old 02-14-2009, 01:16 PM   #2
Join Date: Dec 2008
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Wood subfloor with slab room addition

Floor patch on the lower concrete side should get things levelled out.


The wood floor is more prone to expansion and contraction due to changes in temperature and humidity than the concrete floor. The two subfloors will move relative to one another at the joint.

Also, how were you planning to attach the planks? You're probably going to glue on the concrete unless the floor can be floated. Better to nail or staple on a wooden subfloor unless it can be floated. Awful hard to mix and match mid-job.

I'd float the wood floor over foam, glueing the tongues and grooves, strapping and clamping while it sets. That should also minimize issues where the two subfloors meet. If the wood you selected can't be floated, select one that can be...

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Old 01-08-2010, 09:49 PM   #3
Join Date: Feb 2009
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Wood subfloor with slab room addition

Realized that the job was to big for me. Hired a pro to do the install. He put down 1/2 inch plywood over the concrete and the raised foundation subfloor ( nailed and glued over both after "felt paper"). He glued the floor down over both surfaces.

The new engineered floor is not flat. I did not expect a level floor; I doubt any floor in a fifty year old house is. I have a six foot level that rocks 3/8 of an inch in many places of this 1500 sq install. Is this the industry standard? Some places sound empty when you walk on them; is this normal?

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