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Old 04-24-2008, 08:00 PM   #1
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underpin??? or what?


Im diggen out my basement to get some more head height. Its a old stone house so theres not footings, just some rocks slapped on the dirt and up they went.
My question is, when im done digging ill be about 8 inches below the foudation wall. Do I have to underpin or can I just poor a curb around the base of the wall, and butt my new floor into the curb. Suggestions would be greatly appretiated!!


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Old 04-24-2008, 08:31 PM   #2
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That's a tough one. One thing I'd caution you about is that loads transfer downward and outward up to 45 degrees. So, if you dig down right next to the stone wall below the point the wall bears on the soil, you are actually removing load bearing soil without truly undermining the wall. Whatever concrete you put back needs to be able to withstand the loads that radiate outward from the base of the wall.

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Old 04-25-2008, 06:51 AM   #3
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The basements that I have seen that were dug out were almost all done the same way. At the base of the foundation wall, step in about 3 feet then go down. You will loose the 3 ft all the way around the basement but you will be able to stand up in it.
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Old 04-25-2008, 09:04 AM   #4
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The three feet at the perimeter would leave the load-bearing soil intact.

I'm certain that an engineer could probably design a reinforced curb that could be closer to the footing and cost you less floor space.
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Old 04-25-2008, 12:22 PM   #5
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I'm not sure if I really like the idea of undercutting anything at all, but this is what I have seen in some old homes and if they are still standing, it must be ok.
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Old 04-25-2008, 03:32 PM   #6
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what do you think of this?? Look safe?? Any suggestions. Basically im only going down 8" below foundation wall, then pouring 4" on top of that with a 5" * 12" curb.
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Old 04-25-2008, 09:36 PM   #7
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I'd make that curb as wide as you can stand it. I'd also be sure to use at least a couple horizontal runs of #4 (1/2") rebar in it, as well as vertical bars running horizontal from the slab and up 90 degrees up into the curb...No further apart than 24" on center...12" oc would be the way I'd do it if it were mine.
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Old 04-25-2008, 10:31 PM   #8
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Quote:
Originally Posted by thekctermite View Post
I'd make that curb as wide as you can stand it. I'd also be sure to use at least a couple horizontal runs of #4 (1/2") rebar in it, as well as vertical bars running horizontal from the slab and up 90 degrees up into the curb...No further apart than 24" on center...12" oc would be the way I'd do it if it were mine.
I'll second that but I would check with an engineer or geo type nerd to make sure.
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Old 04-26-2008, 09:20 AM   #9
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Absolutely! Something like this should always involve an engineer.
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Old 04-26-2008, 12:59 PM   #10
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yes true, but they OVER KILL everything just to cover their buts when a simple solution will normally do. We all know that. Im undecieded what to do because I only need and extra 4"!!! ahhh.
Your advice has been great!!! thanks a bunch...


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Old 04-26-2008, 06:55 PM   #11
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yes. I agree. I am doing a BUNCH of work to "make things right" on a place that somebody did NOt get with anyone on. At one point, I say, yea, they overkill, but on the other hand. I wanna "cover MY butt "too! I want this place to be a little overkill and stand, compared to me cutting any corners as was done before..
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Old 04-26-2008, 10:11 PM   #12
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Believe it or not, not all engineers overkill things. I could name you two or three "builder friendly" engineers in my area that will sign off on basically anything. Most engineers are smart enough to know that if they repeatedly cost customers excess money in materials in labor due to their "over-engineering," they won't get much return business.

Express your needs to the engineer, but make your desire to not go too crazy clear, and I am sure they'll work with you.

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