Questions about leveling a floor


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Old 12-17-16, 12:26 PM
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Questions about leveling a floor

I live in South Florida and wanted to get Impact Windows installed, but the front of my house (built circa 1958) was settling so I had to address that issue first. House is stucco covered concrete block construction so I had a contractor come in who attached 7 piers to the foundation, drove piles down until they hit bedrock, and then raised the house to stabilize it. However, I have a floating slab and when the foundation went up the floor didn't move, so I now have a major gap ranging from 1/2" to 1-1/2" between the interior walls and floor slab.

Now that the impact windows have been installed it's time to install new flooring, but I need to address the floor issue first and have some questions:

1. I'm thinking I should first fill the gap with Great Stuff or something similar to prevent the self-leveling floor mixture from simply flowing out under foundation. Yes/No?

2. Can I put something down as a "filler," like plywood or backer board, at the gap's largest points? It will still get covered with at least a half-inch of floor leveler, if not more.

3. I'm also concerned that, if I can't use a filler of some sort, considering how much leveling mixture I'll have to use, the additional weight will just cause the slab to settle even more.

Comments and/or advice from anyone with floor leveling experience would be most welcome. Thanks in advance.
 
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Old 12-17-16, 01:48 PM
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You could look into having the slab raised, called mud-jacking. They drill holes in the slab and pump in concrete grout in a controlled manner to raise the slab. Usually done on outside slabs, but perhaps could be done on yours.

The floor leveler is mixed thin so it flows, and it will flow into the tiniest gaps and even some cracks, so you definitely need to seal off the area to be leveled. It will even flow through seams in the 2x4 wall plate and even under the plate if the slab has any dips. I wouldn't use foam for a 1 1/2 in gap, I don't think it will provide enough support for the leveler after it's poured and hardened and it would be likely to crack and or crumble over that area. I'd probably fill that wide of a gap with mortar or even concrete.

I know you can use small aggregate as a filler material to reduce the volume of leveler. You have to be careful choosing the aggregate size of course. I definitely wouldn't use plywood, but backer board might be ok if lies flat on the slab with no voids underneath and could be adhered. But I would check with the manufacturer of the leveler to make sure backer board would be compatible.

The levelers set fast so you will need lots of help to mix, pour and spread it. You do have to roughly spread it; you can't just dump in the middle and count on it to spread out. And use the recommended primer.

Good luck with your project!
 
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Old 12-18-16, 05:23 AM
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Thanks for the reply, Paul.

I've already looked into mud-jacking and it's simply too expensive an option to consider.

To clarify, the gap is not in the floor itself, but between the floor and the raised foundation, and the sole purpose of the foam would be to create a vertical barrier between the floor and the interior wall to prevent the leveler from flowing out underneath the wall. At no point would the foam have to support the leveler mixture.

I never thought of using small aggregate as a filler and think that's the way to go, but I will take your advice and contact the manufacturer of whatever product I decide to use to see what they have to say.

Thanks again!!
 
 

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