How thick should gravel be under the concrete pool decking?

[KCD]

How thick should the gravel be under the concrete pool decking? Also, are there Code requirements with regard to the minimum thickness of the gravel? For the pool that I'm having built, the average thickness is about 2 inches, with bare spots showing in places. This does not seem adequate to divert water away from concrete pool deck to prevent cracking and buckling.

 

[YippeeSkippy]

Hi there.... code requirements would be something local to you, so most of use would be useless there. But as to ideal cement.. I know the perfect person to ask! paging @onBalance Has the cement all been laid or is this a work in progress?

Maddie

 

[onBalance]

Two inches of gravel is generally sufficient. But the type of soil and the amount of compaction also figures in what is needed.
I don't think that the placement of gravel underneath concrete decks has to do with moving water away and preventing cracks.

 

[KCD]

The cement has NOT been laid for the decking. The soil is clay. The work failed government inspection and is on hold. One reason it failed inspection is that the drawings don't show the thickness of the gravel base. I was hoping someone would be able to tell me "the industry standard or average" for thickness of gravel base. Based on my limited research, I'm thinking the typical deck should have 3 inches of gravel and 4 inches concrete.

For my pool build, it appears that I'm up against a decking crew from heck. Tons of gravel meant to be used as a base for the concrete pool decking have been broadcasted around the lawn using a Bobcat, leaving not enough gravel base for the decking in some areas and causing extensive damage to the lawn. An underground drain pipe on my property has started to leak, damaged in the area where a Bobcat was used to move dirt and gravel. A swale that is used to drain an area with a history of standing water was filled in by mistake; and the area adjacent to the pool decking near the pump was not adequately graded. Consequently, a couple of days of my labor was needed to temporarily repair these areas because of coming storms.

 

[setsailsoon]

Wow! Sounds like a mess and I would strongly suggest you take a different approach. Permits and compliance with local building requirements are normally the builders responsibilities not yours. This should be clear in your scope of work in the contract. When you work the problems for him you become accountable and you enable more bad behavior by the builder.

If it were me I would set up a meeting with the PB asap. Tell him you're concerned about a number of workmanship issues that are causing delays and potential quality gaps that could affect pool use. Also tell him you are willing to work with him to get the problems rectified but he must do his part as well. You should expect to let schedule slide but not incur any additional cost. Make a bullet list of topics like this (I'm making some assumptions so fix as appropriate:

• Gravel was broadcast on lawn now there's not enough for the decking base. How is this going to be addressed without further delay? This will delay the next progress payment and is causing delay to the next item.
• Where are the dimensions for deck construction. Inspector will not approve and you are responsible for permits how are you planning to resolve?
• Your crew damaged a drain pipe with the bobcat. What is your proposed repair and when will this be completed?

This needs to be a face-to-face meeting with the PB not a foreman or supervisor. You need to put yourself on par with the builder not one of his employees.

I hope this is helpful.

Chris

 

[KCD]

The PB is taking care of the inspection part. As far as seeing the PB in person, it's not going to happen for this company, except maybe through a court judgement.

 

[BMerrill]

It is well worth your time and money to have a soil testing company take some core samples for CBR test to determine the minimum thickness as there are a lot of variables in determining the depth of a sub-base, if needed, and type of material to use. If the subase is not the correct thickness and material and not properly compacted then premature cracking of the concrete will occur. The subase will need to extend 4-6" beyond the finished edge of the concrete.

 

[KCD]

Not sure about CBR; keeping it simple, if I do an internet search of how much gravel under a concrete pad do I need for a clay soil, I get 8 inches, which is more than for a sandy soil because sandy soil drains better. It makes my current 2 inches look bad.
If I do another search of how long does it take to build a pool, I get 4 to 6 weeks. My pool has been under construction more than 10 months. LOL That looks really bad, pandemic or not.

 

[KCD]

I managed to get government inspectors involved; and according to them. 4" of concrete, 2-4" of subgravel, AND #10 mesh will pass approval. The concrete patio for the pool failed inspection several times and it's still not finished. The build has been going on about a year and a half now.