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Old 09-25-2010, 12:29 PM   #1
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Foundation Excavation in confined space


I am considering a home extension (1940's 2 story on pier and beam) which will require a 31ft span to be supported between new wet elevation and center of the house (see dwg). My problem is that the structual engineer has advised that i will need an 11ft deep pier in the existing house structure in order to carry the load (adjacent existing stairwell area).

The challenge is how to dig an 11ft deep hole for the foudation in an existing house. Any ideas on equipment that could be used or is this a hand dig? The house is in Houston Texas.
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Old 09-25-2010, 01:19 PM   #2
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Foundation Excavation in confined space


Call in a professional with the correct tools. This is not a DIY project.
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Old 09-25-2010, 02:58 PM   #3
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Foundation Excavation in confined space


understand and will be using a professional was just looking for what i might expect them to be doing i.e. doing my homework as i am sure that many will suggets that can do efficiently
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Old 09-25-2010, 03:16 PM   #4
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Foundation Excavation in confined space


What anyone can do depends on the access to the area. Digging a hole 11 feet deep will probably need more then a Bobcat(4' wide). I don't know if they have an auger that will go down that far.
Try posting pictures of the site and the access to it.
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Old 09-25-2010, 03:48 PM   #5
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Foundation Excavation in confined space


How big(width, area) is the pier? Are you sure you will have 11' feet in the ground? That is pretty deep for a 11' pier that close to the existing construction unless you could very poor soil. The poor soil makes excavating down 11' very tricky and costly. Even auger cast piles might be an option, but only the engineer really know the details and what is there. Both the augering of the hole and the augercast pilings would be pretty quick.

A caisson or a Sonotube could be used and a auguring is quite possible if access is good. It makes a lot less mess and less to backfill and worry about settlement of the replaced soil.

An 11' deep excavation will involve a steel shaft to be installed for safety if people are down in the excavation.

Clearer information on the site elevation the outline of the existing home would help to remove confusion and get better answers. My suggestions and options are worthless if the pier in under the existing home.

Dick

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Old 09-25-2010, 04:20 PM   #6
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Foundation Excavation in confined space


Has the engineer explained the overwhelming reason that caused him to place the pier within the existing house? Seems like an odd ay to design an addition. Most would try to put the support for an addition within the actual footprint of the addition.
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Old 09-25-2010, 08:06 PM   #7
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Foundation Excavation in confined space


Thanks for the feedback. I've had a soils report, structural eng and an architect on the case. The drawing in the original post depicts the area of the new extension. The reason for the pier being in the center of the house is simply that i dont wish to have a column in the space, preferring to use the perimiter walls and the central load point to carry the weight. Of course if it isn't possible to dig 11ft deep then i will need to revise the design. As to the space the property is (1) back to stud (2) resting on piers already (3) has 8ft ceilings. There will be plenty of room width wise just no headroom beyond 8 ft. The enclosed pics give a sense of the space

I just thought there would be simple kit our there to dig 11ft deep in a confined space
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Old 09-25-2010, 08:43 PM   #8
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Foundation Excavation in confined space


I am not an engineer but I am working on a job that needs a good foundation in deep fill. We decided that driving pilings would be more cost effective than digging so deep. But we have solid rock under the fill. Not sure what you have under your dirt.
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Old 09-25-2010, 08:55 PM   #9
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Foundation Excavation in confined space


No offense, but I think you'd have a tougher time with your pier than Andy Dufresne had getting out of Shawshank.

I believe your engineer did the correct thing in specifying and locating the pier. It will be up to you to decide if it's worth it. Only way to do that job is with a pile rig or drilling rig. Don't even think about doing it by hand, unless you want to get buried in that hole.

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