Filling voids under concrete pool deck

Old 01-23-19, 04:17 AM
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Filling voids under concrete pool deck

How would you recommend filling voids under a concrete deck?

The earth under our concrete deck, which surrounds our swimming pool, has settled about 5in from the pool wall toward the middle. So the walls of the swimming pool are supporting the inside part of the deck. The earth is supporting the outside part of the deck toward the middle.

I just want to fill these voids to avoid possible sinking or cracking of the deck.

1) Would you just wash in sand? This may help some but I don't see it offering a lot of support because there is no way of compacting it.

2) Would you fill with concrete? This would be expensive to do the entire deck and concrete shrinks, so I don't know if that is really viable either; minus mudjacking which I cannot do as a DIY.

3) Would you use poly foam? This seems the best option but where do you buy

The only viable option that I can see is to cut out 1 ft square holes and place concrete pads under the slab. Then refill the hole with mortar/concrete thus creating a type of footing. I'd have to do this all around the pool but minus any other ideas seems my only option?

God Bless,
Old 01-23-19, 04:24 AM
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Sight unseen I'd be thinking FlowFill, but don't know how much volume you're looking at, and definitely something I would want references on due to possible damage to the pool.
Old 01-23-19, 04:43 AM
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Look up concrete lifting I had my carport done. Was dropped about 4 inches in one corner and lifted it right up. Get several estimates because I got estimates from 4000$ to 600$. Went with the 600$ one and worked well.
Old 01-23-19, 04:59 AM
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Mud jacking is one option. It is a pro job where they inject cement grout underneath the slab. They can vary the pressure which gives them some control to make sure they fill all the nooks and crannies.

Another option is to inject foam under the slab. I have only recently used it (about 4 months ago) so I can't attest to how it holds up long term. It was a concrete patio slab in sandy soil that had the sand washed out by a hurricane. I used Handi Foam P50007 low pressure foam which I got from Energy Efficient Solutions. Because of the size of the void washing sand in was done first to fill as much of the void as possible but it's almost impossible to wash sand in all the way up to firmly support the slab so the final bit was done with foam.
Old 01-23-19, 09:34 AM
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Thanks everyone.

I will make a few calls for estimates. I already have one company that does poly foam for concrete but expect them to be overpriced. Pilot Dan, I didn't see where the Handi Foam was rated for concrete lifting? It seems to be more an insulation product. If the foam isn't rated for concrete lifting then it won't handle the weight of the slab.

I really wanted to do the job myself because some companies wont guarantee no damage to the pool which I just had $7k worth of work done on it. But I will go ahead and make a few inquiries into mudjacking, etc.


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