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  1. #1
    Join Date
    Jul 2011

    Default Joining two slabs

    We live in Houston, Tx. Our house was built in the 1950's and the addition was added on in the 80's. Oshan has since added pilons to the outer wall of the addition. The addition is still pulling away from the house. Is there a way to now join the two slabs together? Do you suggest an alternate method to keep the addition from pulling away from the house? We are getting cracks all over the place and I fear that the roof will start to pull apart and we will get leeks. PLEASE HELP!! We've called foundation companies, but no one seems to have an anwer for us.

  2. #2
    Join Date
    Dec 2010
    Houston Texas

    Default Re: Joining two slabs

    The guys at Olshan are usually pretty sharp about all things foundation. The Romans has a way to solve this little dilemma by carving a bowtie shaped trench across both slabs then filling the trench with molten iron. When it cools the molten iron shrinks a bit and locks the two together. That is still working at the Pantheon, the Parthenon and a few other structures.

    My only idea; removing a 3 foot wide +/- section of slab so that the two slabs can be attached properly to each other.

  3. #3
    Join Date
    Jun 2007
    Coventry, RI

    Default Re: Joining two slabs

    The first thing you need to do is figure out why the slabs are separating in the first place. I would guess that there is some sort of settling somewhere between the main slab and the additions slab. This could be due to poor drainage or the material under the additions slab was not properly compacted before the slab was poured.

    If you do have settling there is a process know as mud jacking where holes are drilled into the slab and a slurry of cement is forced under the slab. In a patio or walkway situation it actually lifts the slab back to its original height. I doubt in the case of the addition it would fix any settling due to the extra weight of the house on top of it but it could shore it up to stop the problem.

    Your best bet would be to consult with a structural engineer as they would be able to give you advice on how to solve the problem and could tell you what materials to use to tie the slabs together once the cause of the problem is fixed.


  4. #4
    Join Date
    Jul 2010

    Default Re: Joining two slabs

    I would consult an engineer at once. Waste no time.

    Properly done, a new slab is poured after 2' long rebars are inserted 1 foot into the old slab with epoxy adhesive, usually 16" o.c.

    possible solution: cut the added concrete at least 2' along the old concrete but don't cut existing rebars, prepare the base (compact, cover with 6mm plastic), install the connecting rebars on both sides (to the old concrete and to the added concrete) and pour new concrete.

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