Replies

1. 
   Terrence_N._Banbury_NCARB | Nov 19, 1999 02:32am | #1

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   This is very dangerous without some kind of temporary shoring. Don't do it without seeking the advice of a structural engineer. BTW, I am a registered architect and may be more cautious than some.

2. 
   Guest_ | Nov 19, 1999 03:28am | #2

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   Get an experienced GC who's done it before. Most of them have blown out a few walls on their way to gaining the experience neccessary so your's won't blow out. But if they know what they're doing , its not a real big deal. If you're around remodeling long enough, you'll have seen all kinds of solutions to what you're describing. Most concrete form guys don't want to do it because their technigues and forms rely on the concrete exerting pressure in both directions and being resisted by the form tie system. What you need is some one-sided forming, and some shoring, a lot of shoring.
   Once you have the undermined portion of the wall stabilized , then the rest of it becomes rote. So , find someone with experience. Check with a knowledgeable excavator, he can tell you which contractors can handle it.
   I think this is one of those areas where you want to go poured concrete and forget about the block work, but there again, an experienced mason could shore and lay up pilasters to catch your low wall. and then lay up curtin wall to close it in.
   Now, if you disregard this and DIY, just think about the stories you can tell your grandchildren, hmmmmm.
   You could also have someone shore the bumpout addition, take the low block wall right out and pour a footing and relay the wall to full depth. Again, experience counts. Check their liability insurance too !

1. 
   Guest_ | Nov 19, 1999 04:18am | #3

   *I would consider the possibility of contacting some house movers to support the addtion. Remove the block wall adjacient to to proposed addition and build all new wallswith block or concrete.

3. 
   Fred_Matthews | Nov 19, 1999 10:10am | #4

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   I'd consider providing temporary support of the existing, adjacent foundation which would become permanent after construction of the new addition. You can do this several ways, but I would consider using needle beams, beams which slide through a hole punched in your existing wall beneath the sill. These beams are jacked and cribbed to transfer the load. Once the beams are in place, you can excavate for the new foundation. I would consider some of your new foundation sysytem be designed to extend under your existing construction. As a PE, I would advise you to get a competent engineer to sign off on your proposed method of support and construction. This would include specification of cut slopes, determination of how far into take support into existing construction, size/spacing of neeedle beams, etc. As mentioned previously, a house mover could subcontract that portion of the work, or at least provide you w/ the necessary insight on how to proceed.

4. 
   Guest_ | Nov 19, 1999 06:29pm | #5

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   Greetings fellow NE Ohioan!

   I would say (without personally inspecting the site) that you should do this...

   Brace the house from beneath and along the existing foundations in the area of this new addition. This can be done with house jacks and beams. Excavate the area for your new addition and then remove the existing foundation walls in the area of the new work. When you build your new foundation, it should be four walled, meaning that you will be replacing what existed at the two existing walls as well as building the new ones. The new foundation beneath the existing home will now be at full depth and tied into the remainder of the existing. You must be very carefull when supporting the existing house though because you don't want the earth beneath the supports to cave once you've removed the existing foudation and excavated below that depth. This is NOT something I recommend for a DIYer or a beginner contractor. Of course you can always build the addition over a crawlspace also but I imagine you really want a basement. Be careful and hire someone in the know!

   Pete Draganic
   Central Diversified Contracting
   Cleveland, Ohio

1. 
   Guest_ | Nov 19, 1999 08:00pm | #6

   *Agree with pete which reiterated what a couple of others said. It should be done right, the first time.This spring we did an underpinning at the rear wall of a garage to accomadate an addition....(just a slab and one wall and relatively modern construction), without a problem. However on older construction without footings....it can be extremely dangerous. Moreso if the foundation is rubble wall, (seen a collapse due to plumbers digging beneath one). My vote is to jack it...and give yourself a proper foundation.L

5. 
   Jim_T. | Nov 22, 1999 07:38pm | #7

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   Thanks all for your responses-I appreciate the excellent advice.

   Now way in hell is this a DIY project! I'm glad to hear it can be done and obtain a full basement. I agree it's critical to hire an experienced, fully insured contractor to perform this aspect of the addition.

   Pete-you ever get down south to Hudson for building projects?

6. 
   Guest_ | Nov 22, 1999 09:16pm | #8

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   Jim,

   Hudson isn't that far from me at all. I just finished one in Bath, Ohio. Some beautiful homes there in Hudson. Give me a call, I would be glad to have a look at it. Call me at 216-271-6458. I'm in the phone book under General Contractors in Cleveland but I don't believe I am listed in the phone books there in Summit County.

   Thanks,

   Pete Draganic

   Central Diversified Contracting

   [email protected]

7. 
   Jim_T. | Jan 04, 2000 11:39pm | #9

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   I'm considering adding on to my old home here in NE Ohio. I'd like to obtain opinions on my particular situation with my current foundation(s). Here goes:

   The main part of my house has a block foundation about seven feet below grade with a full basement.
   A bumpout addition added about 50-60 years ago is perpendicular to the main house and has a block foundation about 4 feet below grade and is a crawl space. Both foundations do NOT have footers. I'd like to put this new addition in the space at the intersection of the main house and the old addition which forms an "L". In order to excavate this area to pour the footer and lay block for this new addition (about 7 foot below grade), the adjacent wall of the old addition will be temporarily exposed until the new wall is built right next to it. I suspect this may be a very dangerous situation in terms of wall of the old addition collapsing.

   Should I not consider putting an addition here?