# How far down under my house can I legally dig? **URL:** \ **Category:** Factual Questions\ **Created:** [November 8, 2008, 4:34pm UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820 "2008-11-08T16:34:57Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Dilton\_Doiley\_Philosopher\_King](https://avatars.discourse-cdn.com/v4/letter/d/f1d935/32.png) [@Dilton\_Doiley\_Philosopher\_King](https://boards.straightdope.com/u/Dilton_Doiley_Philosopher_King)\ **Post date:** [November 8, 2008, 4:34pm UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/1 "2008-11-08T16:34:57Z")
Assuming that a) I own my house b) I don’t hit any water, sewage, or power lines and c) digging under my house won’t affect the structural integrity of my house or its foundation, how far down can I dig, from a legal perspective? Can I build a five story house under my own two story home? I am imagining something like… digging a stairwell out in my basement floor, and then digging out rooms and whatnot, farther and farther down. Additionally, if I am able to dig down to a certain depth, can I start to dig out, essentially under all the houses in the neighborhood, but so far down they would never know (unless they also dug under their houses) with no legal repercussions? ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [November 8, 2008, 4:39pm UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/2 "2008-11-08T16:39:19Z")
> [@Dilton\_Doiley\_Philosopher\_King](#): > > Assuming that a) I own my house b) I don’t hit any water, sewage, or power lines and c) digging under my house won’t affect the structural integrity of my house or its foundation, how far down can I dig, from a legal perspective? Can I build a five story house under my own two story home? > > I am imagining something like… digging a stairwell out in my basement floor, and then digging out rooms and whatnot, farther and farther down. > > Additionally, if I am able to dig down to a certain depth, can I start to dig out, essentially under all the houses in the neighborhood, but so far down they would never know (unless they also dug under their houses) with no legal repercussions? You can dig down but not out. The problem comes from needing permits and inspections. As you go down you are going to need to support the walls of the hole so they will not fail. Also as you go down you could effect the stability of your neighbors land. ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [November 8, 2008, 4:58pm UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/3 "2008-11-08T16:58:02Z")
You’d need to get a building permit and your property taxes would be adjusted according to any improved house value. You’ll probably only be limited by local building codes. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [November 8, 2008, 5:22pm UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/4 "2008-11-08T17:22:51Z")
> [@Dilton\_Doiley\_Philosopher\_King](#): > > Assuming that a) I own my house b) I don’t hit any water, sewage, or power lines and c) digging under my house won’t affect the structural integrity of my house or its foundation, how far down can I dig, from a legal perspective? Can I build a five story house under my own two story home? > > I am imagining something like… digging a stairwell out in my basement floor, and then digging out rooms and whatnot, farther and farther down. > > Additionally, if I am able to dig down to a certain depth, can I start to dig out, essentially under all the houses in the neighborhood, but so far down they would never know (unless they also dug under their houses) with no legal repercussions? In most jurisdictions of the U.S., from a legal perspective, you own the land within your property boundaries all the way down to the center of the Earth. The exception are properties where the mineral rights are severed from the remainder of the real estate rights (generally only an issue in western states). Any water, sewer, or power lines on your property (not owned by you) should have an easement. You cannot dig under someone’s house or anywhere else on their property without an easement. With respect to this last question, I am actually involved in a project that will involve tunneling under people’s houses, businesses, a railroad line, etc. We are installing several deep sewage tunnels that will run between 30 feet below grade to as deep as 150 feet below grade. Some of the tunnels are being bored in soil, and some are being bored in bedrock, and they will be several miles long. Anyway, we have to get easements from every property owner on whose property we tunnel under, regardless of the depth of our tunnel. ---
**Author:** ![Savannah](https://avatars.discourse-cdn.com/v4/letter/s/b3f665/32.png) [@Savannah](https://boards.straightdope.com/u/Savannah)\ **Post date:** [November 8, 2008, 7:57pm UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/5 "2008-11-08T19:57:39Z")
[Well. Be careful. Don’t be a Mole Man.](http://www.guardian.co.uk/society/2006/aug/08/communities.uknews) ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [November 9, 2008, 12:53am UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/6 "2008-11-09T00:53:08Z")
In some (many? All? It could be an OSHA mandate) jurisdictions if you dig a hole and have humans in the hole at any time deeper than about 20 feet, you need a licensed Professional Engineer to sign off on your design for maintaining the structural integrity of the walls. In some places you need a PE’s approval to go below 8 feet. ---
**Author:** ![MC\_E](https://avatars.discourse-cdn.com/v4/letter/m/c77e96/32.png) [@MC\_E](https://boards.straightdope.com/u/MC_E)\ **Post date:** [November 9, 2008, 12:55am UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/7 "2008-11-09T00:55:35Z")
Don’t forget, with the earth being roughly spherical, the deeper you go, the smaller your owned area is. Think of an inverted, very elongated pyramid. ---
**Author:** ![Boozahol\_Squid\_P.I](https://avatars.discourse-cdn.com/v4/letter/b/d9b06d/32.png) [@Boozahol\_Squid\_P.I](https://boards.straightdope.com/u/Boozahol_Squid_P.I)\ **Post date:** [November 9, 2008, 3:59am UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/8 "2008-11-09T03:59:52Z")
> [@MC\_E](#): > > Don’t forget, with the earth being roughly spherical, the deeper you go, the smaller your owned area is. Think of an inverted, very elongated pyramid. And once you hit the middle, you’re really digging under someone else’s house. So definitely not any more than halfway. ---
**Author:** ![Chimera](https://avatars.discourse-cdn.com/v4/letter/c/8e8cbc/32.png) [@Chimera](https://boards.straightdope.com/u/Chimera)\ **Post date:** [November 9, 2008, 4:49am UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/9 "2008-11-09T04:49:24Z")
> [@Boozahol\_Squid\_P.I](#): > > And once you hit the middle, you’re really digging under someone else’s house. So definitely not any more than halfway. Once you hit the exact center, you’re under everyone’s house. ---
**Author:** ![ouryL](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ouryl/32/6067_2.png) [@ouryL](https://boards.straightdope.com/u/ouryL)\ **Post date:** [November 9, 2008, 5:40am UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/10 "2008-11-09T05:40:01Z")
To dig such in Hawaii, you may need a permit so as to protect the water table. ---
**Author:** ![Tom\_Tildrum](https://avatars.discourse-cdn.com/v4/letter/t/e95f7d/32.png) [@Tom\_Tildrum](https://boards.straightdope.com/u/Tom_Tildrum)\ **Post date:** [November 10, 2008, 5:18pm UTC](https://boards.straightdope.com/t/how-far-down-under-my-house-can-i-legally-dig/471820/11 "2008-11-10T17:18:41Z")
You’re not hollowing out some creepy Austrian-style dungeon, are you? Because that would likely run afoul of other laws. :dubious: