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Underground brickwork

Discussion in 'Building' started by akist, 17 Jan 2019.

  1. akist

    akist

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    Location:
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    Some time ago we built a retaining wall, made out of concrete blocks (those with two holes in them) and iron bar rods. On top of this wall we put about 100mm concrete and buried in it, metal fence posts brackets with 1500mm height fence panels. The wall is about 35m in length and about 1.8m tall.

    After some years the winds blew and pulled a section of the fence over (2-3 panels), but instead of the timber posts snapping, the top layer concrete slab came out in one piece with the metal brackets, posts and panels all still attached to it.

    The reason this happened is because we poured 100mm concrete over the concrete blocks at the top, but there was no connection between the two surfaces, other than the adhesive strength of concrete, and its weight of course. The repair was we threw out the old concrete slab section that had come off, and we poured new concrete over it, but this time we hacked and scored the top layer and drilled protruding screws in it, so as to form a connection between the two layers. This was done a few years ago and we have had some serious winds since then and so far it has held.

    Today we are building a garage conversion/extension and we have finished the foundations and they will come to do the brickwork, and they start by putting lines of bricks on those foundations. The foundations have a very fine top level surface. Thinking in the same lines as above, I realise there will be no connection between those bricks and the foundations other than the weight of the bricks / wall and the adhesive strength of concrete. There will be no iron fixings or grooves/scores on the foundations surface to provide a better connection. I understand that the loads are primarily downwards, but there is a wall and a roof, and when the wind blows it will place lateral forces, just like it did on the fence.

    Could anyone please tell me what you think about this?
     
  2. ^woody^

    ^woody^

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    It's been done like that for centuries. As long as gravity does not change, it will be OK for centuries to come.
     
  3. Leofric

    Leofric

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    A building on concrete foundations is a completely different situation to your fence on top of a retaining wall. Lateral restraint is provided to walls of a building by metal straps fixed to joists and roof timbers (as well as cross walls ) Holding down straps hold the roof to the walls. Make sure the extension is built to comply with building regulations and it shouldn't blow over or slide over the foundations.
     
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