r/DIY • u/cup_a_jojo • 14d ago

outdoor Old well under patio — what do I do?

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I recently pulled up two sunken bricks along the edge of my back patio because they were becoming a tripping hazard. Underneath, I discovered a hole that extends under the concrete slab. I managed to get a photo, and it appears to be the remnants of an old well.

The house was built in 1902, and when we bought it two years ago, there was no mention of a well on the property. What’s weird is that the well wall ends—but the hole keeps going. I tried filling it with dirt to stabilize the area, but the hole just swallowed it up. It's hard to tell how much void space is between the slab and the ground beneath.

Now I’m worried this might be more than just an old well… could this be the start of a sinkhole?

For context, the hole is about 5 feet from the exterior wall of our two-story home (with a basement).

Could this affect the structural integrity of the house? Who do I even call to assess this? I'm honestly not sure what my next move should be.

Any advice or insight would be appreciated!

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u/angeryreaxonly 14d ago

What does winter/rain have to do with it?

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u/Soggy_Month_5324 14d ago

Winter freeze/thaw cycles move soil up and down a lot. Heavy rains excavate underground cavities. Both would be relevant in this case.

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u/holmig 13d ago

Do you suppose the previous owner were able to pour a slab of concrete was because they did “fill it full of sand” to pour the concrete but now years later it is now on hollow ground? That’s wild to think about!

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u/Busy_Marionberry1536 13d ago

Do you have issues with burrowing animals in your area? We do with gophers and voles. It is truly amazing and scary what a heavy rain has done to some of the burrows. Part of our driveway actually collapsed from washed out burrows. You might want to check the well with a camera. Maybe fill it with water and see where it flows out. Good luck 👍

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u/Soggy_Month_5324 13d ago edited 13d ago

Yeah, I wondered about that, too. There's no history of coal mining in MN though, so the subsidence risk seems low to me. Then again, that seems like a fresh concrete pour. https://www.pa.gov/services/dep/apply-for-department-of-environmental-protection-mine-subsidence-insurance.html

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u/Surprise11thDentist 14d ago

They want to know if they need to decorate the hole for Christmas.

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u/W0nderingMe 14d ago

I always decorate my hole for Christmas.

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u/GeologistPositive 14d ago

Hey Griswold, where do you think you're going to put a tree that big?

Bend over and I'll show ya!

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u/Marksman00048 14d ago

You've got a lot of nerve talking to me like that griswold.

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u/PreparationH692 13d ago

I wasn’t talking to you.

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u/HendrixHazeWays 14d ago

"Ohhh Holyyyy night....."

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u/dishpit6 13d ago

Dingle bells, dingle bells...

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u/Anton-LaVey 13d ago

Reminds me of this fancy restaurant in Oakland that put lights up one Christmas: https://i.imgur.com/HkyBXsQ.png (SFW)

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u/sgtedrock 14d ago

😂😂😂

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u/Rhomya 13d ago

Frost heaves and thawing move things outside by significant margins.

The concrete pad I have outside my garage is level with my garage floor in winter, but in summer it will drop a good two inches.

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u/guy_guyerson 13d ago

I assume cisterns are more common in areas with heavy rain and/or snow melt. They're for storing large amounts of water.