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  1. #1
    Join Date
    Jun 2010
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    2

    Default Rubble wall reinforcement

    In Eastern Massachusetts, I have a room addition with a rubble foundation under two sides. This has two or three courses of block atop the rubble foundation and the rubble seems to be stabilised with mortar. The rubble extends about two and a half feet down, and is installed in very hard (alluvial?) gravel. On the eight foot side is a bulkhead opening. On the 12' long side is a bearing wall above with the floor joists tying into into a rim joist. Above this, on the long side is a two story house wall. The cellar hole is dug out to within two and a hlaf feet of the rubble foundation and I dug to the wall a slot in the dirt about twelve inches wide and down to below the rubble to see what's up.
    I want to install a wall on the inside of the long side to go down to 6'+ deep so I can pour a floor and run a stairwell alongside this long wall up to ground level and into a room inside the house.

    Can I pour in stages side ways to form a wall. I have heard of "slurry Wall" construction.
    Is this a viable option over underpinning the house and replacing the rubble with a poured foundation? I would like to do this gradually by myself.

  2. #2
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Rubble wall reinforcement

    Perhaps it's just me --- your description of the site and what is trying to be accomplished are difficult to picture. However, it seems you want to do some excavating and construct a deeper section of basement near the existing rubble stone foundation?

    You need to hire a structural enginner to evaluate the site conditions and what is the best course of action to follow along with structural materials will be used and proper tie in to existing foundation. As well you will need certified drawings to submit for a permit ---- this is one project that needs a permit and inspected.

    I'm not sure what you mean by ..........
    " Can I pour in stages side ways to form a wall. "



    " I have heard of "slurry Wall" construction.
    Is this a viable option over underpinning the house and replacing the rubble with a poured foundation? "

    .......... slurry walls are not structural. Perhaps you're thinking of pumped concrete?

    To be honest, this is one project that should be handled by an experienced contractor ---- it's really not for a DIY'er.


    Just some thoughts.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Jun 2010
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    2

    Default Re: Rubble wall reinforcement

    I have form and poured an number of concrete tie beams, slabs and such and am an experienced carpenter.
    I wondered about the slurry wall technique. It was actually used famously on the World Trade Center where the ground was unstable and sections were poured sequentially. This allowed the existing soil pressure to support the displaced soil.
    Just wondering if this technique is applicable and what is the actual process. It was suggested by an architect.
    The new foundation I want to add would be parallel and interior to the existing rubble wall foundation. I would leave the rubble in place but go deeper beside it. The rubble foundation goes about four feet below grade. The new concrete would go down to about six and a half feet. Then I would pour a floor slab inside the new foundation.
    I think I can excavate a column about twelve inches wide next to the rubble, form one side and leave the other side undisturbed as rubble. This would get short pieces of rebar horizontally , added as I poured the concrete. Then when the column had cured for four days, I would remove another twelve inches and repeat the process,(Or something like that)and working from one end to the other.
    The idea would be to reinforce the rubble wall without removing all the soil adjacent to the rubble at the same time. Also, this would all me to avoid underpinning the house.
    Or is this a death wish disguised as a homeowners project?

  4. #4
    Join Date
    Mar 2009
    Posts
    1,387

    Default Re: Rubble wall reinforcement

    Hi, if you saying you want to dig down next to the rubble footer to dig below it next to it may destabilize the wall and you can have a monumental failure collapse. Consider contacting a basement / foundation contractor for a bid to temporary support the block wall and replace the rubble footer with an new footer and stem wall or block so you get the depth.

  5. #5
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Rubble wall reinforcement

    Quote Originally Posted by edwardreed3 View Post
    I have form and poured an number of concrete tie beams, slabs and such and am an experienced carpenter.
    Then you should be able to appreciate how complicated it is to do what you want to do.


    I wondered about the slurry wall technique. It was actually used famously on the World Trade Center where the ground was unstable and sections were poured sequentially. This allowed the existing soil pressure to support the displaced soil.
    Just wondering if this technique is applicable and what is the actual process. It was suggested by an architect.
    Yep --- the slurry system is used for stabilizing soil in unusual conditions -- but , the slurry itself is not structural. For example -- around here a commercial building was going up near a body of water ( a river ). Since they were going down below grade for footings and foundation , the water table was high and the soil was unstable.
    During excavation , special forms were placed into the trench and filled with the slurry. The slurry not only maintains the hydraulic pressure to stabilize the soil but also displaces any water infiltration. When the concrete is pumped into the forms the slurry is pumped out at the same time -- always maintaining the hydraulic pressure to the surrounding soil.

    As you can imagine it's a complicated process requiring lots of equipment , materials, manpower and know how. Besides , it's doubtful you would be able to round up the equipment and slurry mix from your local home center or tool rental place.



    The new foundation I want to add would be parallel and interior to the existing rubble wall foundation. I would leave the rubble in place but go deeper beside it. The rubble foundation goes about four feet below grade. The new concrete would go down to about six and a half feet. Then I would pour a floor slab inside the new foundation.
    I think I can excavate a column about twelve inches wide next to the rubble, form one side and leave the other side undisturbed as rubble. This would get short pieces of rebar horizontally , added as I poured the concrete. Then when the column had cured for four days, I would remove another twelve inches and repeat the process,(Or something like that)and working from one end to the other.
    The idea would be to reinforce the rubble wall without removing all the soil adjacent to the rubble at the same time. Also, this would all me to avoid underpinning the house.
    Or is this a death wish disguised as a homeowners project?
    You will be undermining the existing rubble stone foundation by going deeper --- there will need to be special consideration as to shoring up the structure.

    Personally , I would probably consider removing that section of rubble stone altogether and put in a new section of full height concrete or block. The exterior can always be dressed up with veneer stone to mimic the rubble stone if you want the look.

    Regardless --- you really need to enlist the services of a structural engineer and an experienced foundation contractor.

    As for the architect -- well let's just say I'd rather discuss structural issues with an engineer.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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