Capped cisterns

[Jack Feldmann]

Curious if anyone has some insight on capped cisterns. House I inspected today had a rise in a concrete floor in a circular shape. The seller of the property said they had covered the cistern when they added some rooms on. The concrete is now raised an inch or so.

MY client, just had the same thing happen on another house he was working on. They opened the cistern and found it about 18' deep with about 8' of water standing in it. But the top had pushed up, breaking the concrete.

I have only seen a handful of cisterns in my entire career, and all of them were open.

Anyone seen this before, or have an idea of what causes it?

[Jim Luttrall]

Curious if anyone has some insight on capped cisterns. House I inspected today had a rise in a concrete floor in a circular shape. The seller of the property said they had covered the cistern when they added some rooms on. The concrete is now raised an inch or so.

MY client, just had the same thing happen on another house he was working on. They opened the cistern and found it about 18' deep with about 8' of water standing in it. But the top had pushed up, breaking the concrete.

I have only seen a handful of cisterns in my entire career, and all of them were open.

Anyone seen this before, or have an idea of what causes it?

Not much experience with cisterns, but a thought about pushing concrete up. This would be much like a pool it is is not kept full of water in that water table in the surrounding soil may be high enough to literally "float". I've seen that a few times in person and many times in photos. Seems like it was WWII that they made some ships out of concrete and yes they did float!

[Jack Feldmann]

Thanks for the thought Jim. Apparently, we as a group don't have much experience with cisterns (425 views and only 1 response).
A structural engineer I know didn't know a lot about them, but surmised that if the intakes were not disconnected prior to capping them, water could indeed lift the cover. I have little to no information about this particular cistern.
My client is likely going to buy this house, even though it had numerous, serious issues.

[John Kogel]

Hello, Jack. I grew up with a cistern behind the house, but it was built into a sandy bank and never shifted.
Yes, a dry cistern will float. It needs a few holes punched into the bottom, hammer and chisel.

I filled a swimming pool with crushed gravel and stones. But first I made sure it would sink. ;)