Concrete Patio Hole/Opening

[iVin]

I have a concrete patio in my back yard. The patio has an opening (5 feet x 3 feet) in it. The opening is about 3 to 4 feet deep and runs further inside about 10 feet under the patio. Please see the pictures attached. I am in the process of filling this hole up, but before I do that I just want to know why this hole and opening was made in the first place. I don't want to fill the hole and then realize that I shouldn't have done that.

 

[nealtw]

Decks never have a foundation under them like that, so someone went to a lot of work to build that.
Do you have a Basement or a crawlspace, can you see the foundation wall from the inside?
Does the deck have a wall below it all the way around?

 

[iVin]

There's no basement or a crawlspace to the house. The opening has walls on three sides and one side the opening goes in a few feet more. It seemed to me that it could be built as some kind of a storage area, but I could be wrong. That was a lot of work. Do you think it is a good idea to fill the pit with earth, compact it, and seal the opening with concrete?

 

[nealtw]

I would use sand, fill it up and then run a hose in there and fill it with water and then fill it with sand again, and again until it doesn't go down any more. That is a the cheap and easy compacting but you may not want to do that if you are subject to freezing.
You do want to fill all the voids as there is no steel in the concrete that we can see so it should be supported from before.
If you tap the deck with a hammer you will be able the hear the difference between supported and unsupported concrete, I would check the rest of the deck, make sure there are no other voids.
This almost looks like someone had an addition in mind?

 

[iVin]

It does seem like someone had an addition in mind and didn't see it to completion. Thanks for your advice. I appreciate it.

 

[bud16415]

Root cellar ???

Be glad you didn’t find this.

 

[Sparky617]

Could it be a cistern? That is a tank for holding rain water?

 

[Snoonyb]

I have a concrete patio in my back yard. The patio has an opening (5 feet x 3 feet) in it. The opening is about 3 to 4 feet deep and runs further inside about 10 feet under the patio. Please see the pictures attached. I am in the process of filling this hole up, but before I do that I just want to know why this hole and opening was made in the first place. I don't want to fill the hole and then realize that I shouldn't have done that.

Several possibilities come to mind.

However, have you taken the opportunity to ascertain whether or not something like a natural disaster shelter may have been permitted, and not completed?

Or a root cellar?

Or would the cost benefit in completing a project, better serve you than abandonment?

 

[thatguy188]

Whoa. Might want to check with the previous homeowner. Maybe they used to hide bodies in there :rofl:

 

[slownsteady]

"It puts the lotion in the basket...."

 

[BridgeMan]

Concrete block would have been a poor choice for a cistern, as it's too porous and would allow (lots of) water to seep through it. Before sealing it up, however, it wouldn't hurt to poke around on the bottom floor to make sure it doesn't have some water valves or sewer line cleanouts--either or both of which could have you talking to yourself for years to come, as you're removing all of the stuff you filled the hole with.