# Hollow Sound Under Concrete Pool Deck



## stick\shift (Mar 23, 2015)

I'd see why it sounds hollow first and if there's really a void, address why it's there.


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## jlhaslip (Dec 31, 2009)

Drag a chain across the concrete and the sound will change when the concrete is hollow.
Fill the void using a grout pump and slurry mixture. Drill holes to allow for the pump to be used.


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## danpik (Sep 11, 2011)

The ground under the concrete settled. This is a common problem with new inground pools that get done quickly. Poor soil/fill compaction. 

In the factory where I work, we were cutting new coolant trenches one time and when we pulled the sections out we found voids under the floor big enough to crawl into. Since the floor supports machines weighing in at 3-4000 lbs and more we had a grout pumping company come in. They used a sonar machine to find all of the voids and then filled them with grout. The real surprise was how much quieter the plant was after that was done.


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## CountryB (Aug 4, 2016)

Like said by others - its common around new pools. When my pool was built I was told it's best to wait at least a year before putting down any decking. Even though the dirt was compacted around the pool trench it is most always going to be some settling. 

But no one wants to wait a year and deal with the mud pit that will form around the pool edges in the mean time. So I did a paver deck instead of poured concrete. And, sure enough, two years later I'm removing some pavers and filling in areas ( actually a couple of areas). But at least with pavers, you can remove them and replace them so it's not noticeable.

At this point it might be a toss up whether to just spot repair now (and probably do it again next year in a different spot) or break up and remove the concrete completely, fill in the low spots, compact, and then switch to pavers.


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