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Oversite concrete

Discussion in 'Building' started by Matt 81, 28 Aug 2018.

  1. Matt 81

    Matt 81

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    Hello all, I'm new to this so please be gentle!

    I've got to pour my extension oversite concrete at the weekend and am not sure how to level it as the finished height of the concrete will be within(lower) than the new brick / blockwork perimeter wall.

    I have ufh going in so the 100mm celotex will be on top of the concrete,then 65mm screed
    My brickie has built up 2 courses of block ( up to damp )for the inside skin of the cavity wall.

    I know it doesn't have to be spot on level but will need a good tamp against something and some sort of guide as to the correct depth. Obviously I can't put level pegs in!

    I also have to put steel in I'm planning on putting this in first on 50mm concrete broken edgings to hold it off the bottom and then putting scaffold boards over the steel to barrow it across. Unfortunately I can't pour straight in from the truck.
    Does this sound like the best way?

    I'm sure I'm over thinking this and there is something easy I'm over looking!

    Hopefully someone can help!

    Thanks

    Matt
     
  2. tomfe

    tomfe

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    It does not need to be too level however the flatter you get it the better.
    You can make L shaped timber to hold your tamper batten or just use the brick course as a guide.
    Support the scaffold boards on bricks between the mesh don't rest it on the mesh unless it's well supported as it might kick up.
    You can add pegs in and put your DPM over the concrete.
    Why are you adding steel into your slab?
     
  3. Matt 81

    Matt 81

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    Hi tomfe,

    Thanks for your reply

    The design spec says
    150mm hard-core
    Blinding
    Dpm
    Concrete reinforced with A142 steel fabric
    100mm celotex
    65mm screed

    I'm just following that. Could it be because there's a soil pipe running through it?

    The problem with the tamping is that due to the dpm I won't be able to see a brick course I'm not sure I understand the L shape tamping beam, would the short part of the L be cut so it is level with the top of the clockwork when the concrete is at the correct depth? How would this work where the slab abuts the existing house wall ?

    There is also a 25mm upstand to surround the slab
    I need to check this as I think it should surround just the screed?

    Sorry for all the questions
     
  4. tomfe

    tomfe

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    Insulated up stand goes in your screed in this instance.
    You can fix a batten to your house at the correct level.
    A142 mesh is anti cracking, it's not normally used (you'll never find it in older properties, larger slabs do need some control over cracking) just to reduce costs however I like to use it.


    upload_2018-8-29_9-17-14.png
     
  5. Matt 81

    Matt 81

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    Hi tomfe
    Now I understand

    The slab is 31 Sqm ( not sure if that is deemed large or not?)

    The steel is about 130 quid so not a ridiculous cost, it's just another extra!
     
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