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  1. #1

    Default Concrete Block Foundation not filled

    We are adding a fairly large addition onto our house with a full basement. The builder is using 12 inch concrete block to build the foundation which is 22 feet wide and about 35 feet deep. We thought they would pour concerete into the holes of the blocks to make the foundation stronger, but they said it doesn't need to be filled and is strong enough. About 6 feet of the basement is under ground and we are adding 2 floors above. Should I worry about the foundation being strong enough with out the reinforcement of poured concrete and rebar in the block holes?? How would I know when pouring conrete into the blocks is neccessary?

    Thanks,

    Jason

  2. #2
    Join Date
    Aug 2007
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    Default Re: Concrete Block Foundation not filled

    Asssuming the contractor pulled a permit, the building inspector would not sign off if incorrect.
    Anyway a 12" block wall that is 6 ' underground assuming a 8' or so height is fine & meets all codes(except seismic possibly) that I know of.
    That said I still think residential construction would benifit from at least horizintal reinforcing 16" o/c just to prevent cracking & strengthen the wall a bit. It all has to do with cost though.

  3. #3
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    Default Re: Concrete Block Foundation not filled

    I got around to checking the IRC 2003 & depending on the type of soil & height of wall, you are getting close to where a 12" cmu is required to be filled or reinforced.
    seismic or hydrostatic pressure from groundwater is another issue.

  4. #4

    Default Re: Concrete Block Foundation not filled

    Thanks for the info ed21. I know the walls are just over 8 feet, but I'll double check. The new ceilings will be 8 ft high in the basement. Is there anywhere I can see the IRC 2003 without having to pay $100 for the book? I'm a believer in building something as strong as you can assuming it will never come down. But just like you said it's probably a matter of cost to the builder. I wish the builder would offer options ahead of time. I can see now how easy it is to add another 15% to your final costs.

  5. #5
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    Default Re: Concrete Block Foundation not filled

    No ****** source that I know of, but their could be.
    Your local code might be different. Codes are often available in the reference section of the library.
    Call your local building department & see what info they have. They often have guidelines/handouts about common questions for residential work. The building departments where I am are usually quite accommodating.

  6. #6
    Join Date
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    Default Re: Concrete Block Foundation not filled

    It would have specified on the engineered drawing and would have been approved by the permits department if the blocks required being filled or not . If it's on the approved drawing and the contractor hasn't done it accordingly then they better stop and correct it.

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