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What to use for temporary props on collapsing brick foundations?

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  1. #1
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    Default What to use for temporary props on collapsing brick foundations?

    Hi folks,
    I live in a 100 year old weatherboard cottage on a slight slope with terrible foundations. There are some brick piers under the house but they have almost non-existent mortar. The edge of the house is resting on a solid brick wall 7 courses high which has the same problem - the mortar is crumbling. As a result, one part of the brickwall on the lower corner is bowing out badly and the weight of the house is pushing it out further. Over the last three years it has gradlualy gotten worse - now the southern half of that brickwall is a full brick lower than the northern part.

    Im broke but Im also concerned to try to stop the collapse of the house! I keep expecting to come home to find that the wall has fallen down altogether.
    I've looked at getting Acrow props to at least help stabilise the wall by taking the weight from the crumbling brick wall and thus slowing the collapse but the smallest that we have here Size0 is too long for the space.

    What should I use? and any other advice? (apart from getting another job to pay for new underpinning)

    cheers
    kaz

  2. #2
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    Hi Kaz, I had a similar problem on one wall of my house. Basically in my case the bottom plate had rotted out. Yours sounds more structural though. It does need to be dealt with fairly urgently or, as you say, you will come home one day and find that corner on the ground. But weatherboard houses are fairly tough and can survive a lot more than the brickwork that is holding it off the ground.

    The reason the mortar has disappeared is because it was a lime-based mortar which, over time, tends to disintegrate. Same problem here but a stable soil so the house is still rock solid, even though there is no mortar in the stonework.

    In the mean time, I suggest you look at the drainage situation. Is there a leaking downpipe, or one that discharges directly into the ground near the spot that is subsiding? Is it the damp side of the house? If there is a damp problem, then installing some effective drainage should at least slow, if not halt the process and you can then sort it out in your own time.

  3. #3
    1K Club Member Pulse's Avatar
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    Hi Kaz,

    I made up some props using a scaffold threaded footplate with a length of 50mm scaffold pipe with a plate on top. RMD sold me some. They are called universal long solid jacks. Kennards had some 00 acros but price adds up quick when you hire.


    Cheers
    Pulse

  4. #4
    Old Chippy 6K
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    This doesn't need anything too complicated as a temporary fix to stop further collapse. You simply need to makes up some timber wedges if you are able to do so or just buy some of the larger plastic wedges from the hardware store.

    You need a sole plate for each temporary pier/ strut/ stump - ie: a piece of timber to sit on the ground to spread the weight from the upright post. You need lengths of timber - 90x45 will do generally, but can be 90x90 or 100x50 or 100x75 - just good solid pieces and can be hardwood or softwood - best if secondhand seasoned. You might need a plate for the top too so you can spread the load across two joists for example if you can't get directly under a bearer.

    You level out an area under where you need to add support so your sole pate will sit flat (it need only be 300-400 long and can be 90x45 or 150x45 - again just a good solid piece). measure the distance from the ground to the sub-floor member you will be strutting to (bearer or joist) then take off the thickness of the bottom plate (and top if using one) and the thickness of the pair of wedges when even (ie: when equally opposed) and add 10mm or so to allow for wedges being hammered tight.

    Then it is matter of assembling and hammering tight - sole plate then post then bearer or joist (or top plate then other). Depending on access you can use the wedges at the top or the bottom. The advantage of wedges is that they allow adjustment as you are doing adjacent supports and over time if the soil dries out or gets wetter.

    The same principle can be used without wedges, but with a decent hydraulic jack (say 10T) - have the ground levelled off and measure up and cut the plates & posts adding whatever you reckon might be OK to lift (no more than 10mm unless you really know what you are doing) and have them ready. Jack up, place the supports and let back down.

    Important to not try to lift more than a few mm just so the new supports are tight - the new supports are additional and intended to add to the original structure temporarily - not replace the existing.

    The bigger job of raising and replacing support is bigger and more difficult exercise and not really a DIY unless you have pro advice and assistance. But by adding supports as described - around perimeter and in where the internal piers are, can extend the need for quite some time and will mostly cost you your time - you can source suitable timber cheaply.
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

  5. #5
    1K Club Member autogenous's Avatar
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    Pictures?
    https://www.instagram.com/perth_bricklayer_wa


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