# Filling voids under concrete pool deck



## Ralph III (Oct 7, 2011)

Hello,
How would you recommend filling voids under a concrete deck?

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

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

1) Would you just wash in a sand/mortar mix? 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 as with mudjacking? This would be expensive to do the entire deck and concrete shrinks, so I don't know if that is really viable either.

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



I have two 16in x 16in holes cut into the deck at the moment where I added some water features. I am just contemplating placing some concrete pads under the deck at these holes for support. I will then fill the holes with mortar/concrete. I won't be able to fill all the voids but I will in essence be creating pillars for the deck. Of course I will have to do this all the way around my deck but seem my only viable DIY alternative? 



God Bless,
Ralph


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## Windows on Wash (Aug 30, 2011)

If you want it to be comprehensive and fully supported, mud jacking (or similar confined space filling via a proper rig is going to be your best bet.


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## Nealtw (Jun 22, 2017)




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## Canarywood1 (May 5, 2012)

For the problem you describe the guy's that do mud jacking are the ones that will use foam instead of grout to fill the void, best to check with them though as some use it and some die hards don't.



I see Neal and i were typing at the same time.


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## Ralph III (Oct 7, 2011)

Hello and thanks for the replies!


Yes, yes. I know what mud-jacking and poly foam are I just wanted to know if anyone had done such as a DIY?


One company that uses poly foam won't touch my deck because they do not want the liability in case the foam were to push my pool sides inward. Their method is to see 1/10 rise minimum as that tells them all voids are filled. 



Another company that uses poly foam is scheduled to look at my deck late next week. I will also call a few other companies that specialize in mud-jacking.


My problem is that I think all of them are going to be to expensive. We just spent 7k for pool repairs and a new liner so I do not have another 2K to spend on our concrete deck at this time which doesn't require immediate attention anyhow. If it were only $700.00 or so then I'll jump on it but I don't see it. 



If I could do it as DIY project then I could simply do some now and more later. I could eventually finish everything in a year or so. 



Thanks,
Ralph


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## Canarywood1 (May 5, 2012)

That is not a DIY project as specialized equipment is involved.


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## Ralph III (Oct 7, 2011)

Canarywood1 said:


> That is not a DIY project as specialized equipment is involved.


Yes, specialized equipment is required IF you are interested in jacking up the concrete.


I just want to fill the voids without jacking anything up. I've spoke with one company that uses the poly foam (2 part) which has to be heated and mixed at 150 degrees. However, you could just simply pour it into a void if desired.


Again, the question is whether anyone has done such as a DIY?


Thanks,
Ralph


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## Nealtw (Jun 22, 2017)

If you just want to fill voids, sand and water and repeat until full.


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## stadry (Jun 20, 2009)

*core drill some 2" holes & pour in grout,,, it will flow & settle out,,, repeat the next day & more til the voids are filled,,, be patient,,, if impatient, buy 1 from kenrich.com*


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## Ralph III (Oct 7, 2011)

Thanks and I am considering some advice given.


I may be able to pack in a sand/mortar mix some two to three feet around my concrete cutouts. I could then place the concrete pads in and fill the holes with non shrink mortar. So this will give me some quick and excellent support in areas that most need it without breaking the bank.


I can then drill or cut more holes into the concrete and pump the rest with mortar as stadry suggested. That could be a done over a period of time but eventually the entire slab will benefit.


Thanks again,
Ralph


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## SallyLawrence (Oct 21, 2020)

Hi guys, thank you for your ideas, besides, you reminded me that I can find a lot of useful content on YouTube.
Ralph, I wonder what you chose and if you like the result.
If we talk about me, I hope that I can finish my pool this spring, because my family has been waiting for it for a long time. In our area, all the pools are closed due to lockdown, so having our own pool in the backyard is an awesome advantage for us. You will probably laugh, but my wife has already bought all the necessary equipment for the pool and even a pool cleaner. By the way, if you are looking for a pool cleaner, then I recommend you to look at these reviews https://homendgarden.com/best-pool-cleaner-reviews/. We ordered a Pentair and I hope that it will help us keep the area around the pool clean, I just need to finish it.


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## Ralph III (Oct 7, 2011)

SallyLawrence said:


> Hi guys, thank you for your ideas, besides, you reminded me that I can find a lot of useful content on YouTube.
> Ralph, I wonder what you chose and if you like the result.


Hey Sally,
I just washed sand into the voids and packed it as best as I could. I then used concrete/mortar to fill in the 16in x 16in concrete cutout. I will paint the concrete pool slab at some point so it won't be noticeable after that.

The voids under our concrete decking allowed me to run #8 copper ground wire all the way around the inside perimeter of our swimming pool. I also ran #8 copper ground wire around the outside perimeter as well. I then washed in the sand over a few weeks. 

So my pool has equipotential bonding all the way around it now whereas it didn't before. Actually, I've only done the one half. The girls were still getting a tingle on the other side (without boding) but once they come to the side with the equipotential bonding it dissapears. So that obviously works. I will be completing the other half this spring sometime. 

God Bless,
Ralph


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