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Old 09-26-2010, 12:41 AM   #1
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digging out "crawlspace"


Not really a crawlspace, more like a "space sealed off since 1907 that is only a foot or so deep at most"

Anyways, I started reading about digging out crawlspaces. I opened my trapdoor I had made last year, and started digging along the rock wall. 10 inches became 20 inches. One thing that bothered me, is that the rocks don't appear to be mortared together (I could stick the tip of my shovel under the second rock, and pry up on it, although it didn't go very far).

Was it common to build a rock foundation, without bonding the rocks together? How deep could (or should) this wall go? I'll be so excited if I can end up with a decent sized crawl space (or hell, a full sized basement). It kind of feels like a treasure hunt, but damn is it a lot of work! I am a little concerned, that the soil is damp underneath, but perhaps this is normal and won't be an issue.

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Old 09-26-2010, 02:44 AM   #2
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It sounds like you are opening Pandora's box, and if you go digging more you are going to end up needing to jack the house up and put good supports under it. If you want a basement, roll up your sleeves and get help from someone who is good at blocking up buildings and letting them down on new foundations. Good luck. j

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Old 09-26-2010, 03:05 AM   #3
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One thing that bothered me, is that the rocks don't appear to be mortared together (I could stick the tip of my shovel under the second rock, and pry up on it, although it didn't go very far).
e.
If they are in the dirt, they may not be. The dirt is adding a lot of lateral support to the stone pile (in the shape of foundation walls) and the stone pile is supporting your building.

Remove either one and the house falls down.
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Old 09-26-2010, 03:24 AM   #4
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If they are in the dirt, they may not be. The dirt is adding a lot of lateral support to the stone pile (in the shape of foundation walls) and the stone pile is supporting your building.

Remove either one and the house falls down.
Anything wrong with digging all the way down, on a small section of the wall, that isn't under a floor joist? Just to see how far it goes, and if it is in fact mortared or not (which is doesn't look like so far).

Is there an acceptable depth I can dig down to then, to at least have some sort of working space so I can get a midspan support under one of the floor joists?
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Old 09-26-2010, 06:54 AM   #5
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It would likely be much easier investigate from the at the exterior, by just probing with a piece of rebar or similar.
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Old 09-26-2010, 10:07 AM   #6
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Whether or not your walls are mortared, the soil is effectively stabilizing the wall. Once you remove the soil, you are converting an earth stabilized wall to a freestanding wall. As previously noted, you run the risk of wall failure, which can be sudden and catastrophic. I recommend that you stop immediately, and retain a competent professional to advise you on how far you can go (if at all) in your downward quest.
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Old 09-26-2010, 10:33 AM   #7
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Reading this thread makes my *** pucker!
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Old 09-26-2010, 01:47 PM   #8
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Originally Posted by Tonglebeak View Post
Anything wrong with digging all the way down, on a small section of the wall, that isn't under a floor joist? Just to see how far it goes, and if it is in fact mortared or not (which is doesn't look like so far).

Is there an acceptable depth I can dig down to then, to at least have some sort of working space so I can get a midspan support under one of the floor joists?
Unless you can PROPERLY and adequately support the building independent of the current foundation, I would strongly suggest not removing the soil at all. Not saying it couldn't be done. I actually have a friend that did just what you are doing from a similar type of construction. He is a degreed engineer so he had the benefit of his training to design proper structural support in his situation though.

He started with the thought of repairing the foundation under a corner of the building and attached porch. Once he started, it turned into the addition of a complete basement and proper foundation to replace the existing foundation similar to yours.

This can be very dangerous and can cause a lot of damage (read: total failure) of the structure should something go awry.

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