Asked on Apr 24, 2012

Pool deck is sinking...what can I do?

by James
I moved into a house where the pool deck was cracked and sinking...about and inch now since I moved in. I just discovered that the pool drains on either side of the deck were clogged and the water was running back under the deck and then out, leaving several inches of air space between the deck and the soil. I have repaired the drains, but the damage is done.
Short of removing deck and reinstalling, what can I do for the 20% of my pool deck that is unsupported? Cement injection? Will this "raise" the deck at the crack back to it's original height?
The pool itself, fortunately, is fine.
  11 answers
  • KMS Woodworks KMS Woodworks on Apr 24, 2012
    This trick is also called "mud jacking" and this is about your only option short of deck demo.
  • James James on Apr 24, 2012
    Thanks for the answers, but I'm still hoping for more ideas. I am sure there is not a VW buried under my deck! :o) I've fixed the drainage problem and it should not get worse, I just need to figure out the best way to support the deck area that is sinking. Is there any Do It Yourself ways to fill in the missing soil?
  • KMS Woodworks KMS Woodworks on Apr 25, 2012
    Mud jacking is not very DIY...the equipment is pretty specialized. I have never looked into whether or not this equipment can be rented? If so the learning curve might be pretty steep. I have done some minor versions where some animals had burrowed below a patio the case I worked on the "edge" of the slab was still accessible and I added some peagravel...Pea gravel being a bit like small marbles it tended to help fill the hole by just rolling down and stacking up. I used a narrow metal rock bar to tamp it in place.
  • If your speaking of an in-ground pool, it sounds as though one or two things can be happening. If the soil was not properly compacted below the slab(s) then they will need to be pulled up and the soil re-compacted and then redone. If however your seeing pool water going down more then it should, you could have a leak either in a pipe to the filter system, or the pool itself. The water running under the slabs can cause all sorts of erosion. I would steer away from mud jacking if its close to the pool area as the pressure could push the pool wall in. If by correcting the water run off due to poor drainage, then you simply need to replace the cement slab. Not fun, but its the proper way to do this.
    • Our old pool is in serious need of a reno. . Pea gravel all cracked and broken.. pool coping also.. seems we have a leak somewhere as we lose about 2 inches of water a daday.this pool is a mess. Looking for as inexpensive as possible way to fix and also water stands next to house due to deck dropped at house.
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  • James James on Apr 30, 2012
    I am quite sure the loss of soil was only from the rain erosion and lack of proper drainage, Now that the drainage is repaired, I'd like to fix the sinking deck. I have found epoxy injection kits online and wondered if anyone has had success with these. I can live with the existing cracks and sunken portions...but certainly don't want it to get any worse. Thoughts??
  • Do not waste your money on epoxy kits to seal the cracks. You can use a good quality silicone caulk and achieve the same results if all your looking to do is to hide the cracks. Fiberglass resin will do the same thing. I would look into mud jacking first to make the slabs level again. Any slopes will draw water to the cracks which in return will cause additional settlement. Sealing the cracks will only allow water to pone until it dries from the sun. Winter you have a icy condition that someone could slip on.
  • David Johnston David Johnston on Apr 17, 2017

    Had one, similar wash -out. Just wanted to make sure it did not drop and further. Used scissor jacks and a piece of uni strut across them Dug out a trench to place the jacks ran the unistrut across the top. backfilled with dirt and packed with a long wooden dowel 4 foot in. During the process, I actually raised the deck about 3/4 an inch. Since it had only dropped 1 1/2, i went ahead and jacked up the scissors. Finished packing the dirt and added paving stones around the outside to hold the new dirt in. 1.5 years later, no issues.

  • Rob Rob on Jun 20, 2017

    I have had "foam" jacking done. It has held up well. Through my research I have heard that mud-jacking can add weight and thus sink again. It was a little less in the way of cost, but less holes to be patched.


    Inground pool. Was like this when I moved in. The individual slabs are raised 2 to 5 inches around pool on one side. Soil was built up on this side so it was suggested that I dig it out and jack it up and then support with more concrete. Do you have any other suggestions.

  • John Meager John Meager on Nov 15, 2019

    Polyurethane Foam will solve your problem!!! The foam is lightweight but very sturdy. Holes are drilled into the slab wherever a lift is needed. These holes are no bigger than a dime and are easy to seal over. When a slab sinks its most likely because the soil beneath it was not properly packed before setting the concrete. Thus, environmentally the dirt is washed away and leaves a "void" which causes the slab to sink. Polyurethane is durable and can last for a very very long time (years) without needing a touch up. Polyurethane for me was the best way to go and a fast fix.