Structural Engineering Question - 12 Inch Walls

[JMPool99]

Our pool has 12 inch walls all the way around. The engineer told us that normal shell walls are 6 inches thick if there is only one "curtain" of steel. Builder did 12 inches to make the pool stronger, but the engineer is saying that 12 inches thick without a second layer ("double curtain") of rebar could lead to cracking issues. We are in an area with expansive soils. Soils engineering did not call for a double curtain.

I know this may a bit more involved of a question but curious if any engineer types out there have thoughts on the thicker (12 inch) walls all around and only a single curtain of #4 rebar used.

 

[ajw22]

You have some pictures of the dig showing the rebar?

You have pool plans stamped by an engineer?

What plans are the builder using?

 

[Oswald]

I am not a pool building expert by any stretch, but it seems really odd that they would build something different from what the engineer specified. That seems.... odd to me.

 

[JMPool99]

AJW - Yes, we have stamped plans by structural engineer. I found out that the soils engineer (we had to have a full soils report) is the engineer who suggested going 12" thick on all walls with #4 bar. So, the builder didn't make the decision on his own, he did it based on the soils engineer. My concern of course is that the soils engineer isn't a structural engineer. Unfortunately, like most, I trusted the processes and found out about this by chance when I asked the structural engineer a question two weeks after we already have water in the pool. So at this point I'm just hoping for the best -- but I'm definitely curious on whether the 12" thick without double re-bar would be an issue. All the concrete tested at close to 6000psi, so that's good at least.

I've attached a couple of photos.

Thanks!

 

[ajw22]

The builder should not have changed the build specification without consulting with the structural engineer who stamped the plans.

The rebar pic you posted shows a lot of rebar closely spaced. Definitely more then the minimum required.

You need to document what went on between the structural engineer, soils engineer and builder and put them on notice. If you get cracking the structural engineer can now look to pass liability off to the builder as he did not build according to the plans the structural engineer supplied.

 

[JMPool99]

Thanks Allen, appreciate it.

 

[JMPool99]

I actually spoke to the structural engineer today and got some good info. Yes, should have more rebar, but unlikely it will cause any issues. Will not cause an structural issues -- in fact he said the extra concrete does make it stronger and fortunately #4 bar used everywhere. If anything happens, it may be "micro cracks" (he used a more technical term). This could cause water from soil to get in and hydration (curing) to happen in the concrete. The byproducts of this reaction could lead to cracking in the plaster. Usually this takes years and it's very rare he said.

All that aside, it is odd that the builder did this under the direction of the soils engineer (12 inch walls) without consulting the structural engineer.

 

[ajw22]

I think your pool shell will be fine.

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