support existing foundation/single pour/or sections
I am considering building a workshop under my house. Have to dig out
the dirt. I will be digging down anywhere from 3.5' to 5.5' under existing foundation. Plan to pour new wall under existing foundation. Will have house resting on crib and beams. Do not want to take out existing foundation. Walls are from 3' high and go down to 18". Would prefer to make new wall under old foundation. PROBLEM: I will have to undermine the existing foundation. Remove dirt. While this is in process, is there any way that I can support the existing foundation? It seems that the weight of the foundation will be to heavy for the crib and beams support system. 1) pour columns and footing with rebar in them. Every 8'. Columns will then be hidden/buried in the TOTAL foundation pour. COLD JOINTS? Leakage, Unstable foundation due to two pours? 2) Steel bar with plate on top and bottom? How thick would the bar have to be? Steel bar placed on footing. Bolted under old foundation? 3) I have looked up permajacks. To expensive to leave in the concrete pour. Was trying to dig out and have one continuous pour for the new foundation. The other thought was to pour the new foundation in sections. Jam rebar 2' into dirt adjacent to new wall form. When wall is poured, rebar will be exposed when digging out the next section. Attach next set of rebar to new wall. Was advised that this may allow water leakage in cold joints. Planning to us a meridrain system against the dirt (outside of the new foundation wall). Any suggestions? Mark |
support existing foundation/single pour/or sections
wrote in message ps.com... Any suggestions? Mark You would have to be nuts to try and do this job yourself. |
support existing foundation/single pour/or sections
|
support existing foundation/single pour/or sections
On Mar 24, 7:43 am, "RicodJour" wrote:
wrote: I am considering building a workshop under my house. Have to dig out the dirt. I will be digging down anywhere from 3.5' to 5.5' under existing foundation. Plan to pour new wall under existing foundation. Will have house resting on crib and beams. Do not want to take out existing foundation. Walls are from 3' high and go down to 18". Would prefer to make new wall under old foundation. PROBLEM: I will have to undermine the existing foundation. Remove dirt. While this is in process, is there any way that I can support the existing foundation? It seems that the weight of the foundation will be to heavy for the crib and beams support system. 1) pour columns and footing with rebar in them. Every 8'. Columns will then be hidden/buried in the TOTAL foundation pour. COLD JOINTS? Leakage, Unstable foundation due to two pours? 2) Steel bar with plate on top and bottom? How thick would the bar have to be? Steel bar placed on footing. Bolted under old foundation? 3) I have looked up permajacks. To expensive to leave in the concrete pour. Was trying to dig out and have one continuous pour for the new foundation. The other thought was to pour the new foundation in sections. Jam rebar 2' into dirt adjacent to new wall form. When wall is poured, rebar will be exposed when digging out the next section. Attach next set of rebar to new wall. Was advised that this may allow water leakage in cold joints. Planning to us a meridrain system against the dirt (outside of the new foundation wall). Any suggestions? You can jack up and use cribbing on anything...just maybe not your personally. The sectional method of underpinning is more common for shallower excavations. I think you need to call in some pros. Your workshop probably wouldn't be so useful with your kitchen sitting in the middle of it. R The reason I ask, is that I have been to two architects, two engineers, 4 contractors. Everyone speaks from their own level of knowledge. Each being very informative and accurate. But the whole picture is not spelled out unless one asks all the questions. Just trying to find solutions to as many questions that come up for me. All the drawings have been approved by an engineer. Supporting beams/footings. The final question is one that I started with. How to support the wall when I am digging out. How to support the wall during the pour. The best way to do the job without spending a fortune. Mark |
support existing foundation/single pour/or sections
wrote:
The reason I ask, is that I have been to two architects, two engineers, 4 contractors. Everyone speaks from their own level of knowledge. Each being very informative and accurate. But the whole picture is not spelled out unless one asks all the questions. Most architects would not know where to start with that sort of underpinning. It sounds like you're still shopping around for a design. No one is going to offer complete details until you cough up some money. If you've already paid for the design, and it's not spelled out how the work is to proceed, you've only gotten half of a design. If you have hired the engineer and they have not provided a preferred method of underpinning, and left it entirely up to the contractor, I don't think very much of your engineer. Just trying to find solutions to as many questions that come up for me. All the drawings have been approved by an engineer. Supporting beams/footings. The final question is one that I started with. How to support the wall when I am digging out. How to support the wall during the pour. The best way to do the job without spending a fortune. My car is misfiring - what's the correct timing? You just asked a similar question. No one knows what your house is like, different areas of the country mean different things when they say "foundation", soil conditions, etc. You get the drift. What sort of contractors have looked at your project in person? Local foundation contractors will have their preferred way of doing things and will be familiar with local practices, construction and soil conditions. They'll also probably have an engineer on staff or a business relationship with an engineer. They'd be able to provide one- stop shopping for your job. No one on a a newsgroup can compete with that sort of head start. Smaller contractors will probably opt for the sectional method of underpinning as it requires less equipment. Larger contractors and house movers won't blink twice at jacking your entire house up. BTW, unless you have faulty foundations jacking the house up instead of digging down, might be a better way to go. Zoning, cost and aesthetics would be the main concerns. Again, only a local contractor would be able to make the definitive determination and tell you what things would cost. R |
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