Are expansion/movement joints needed?

Discussion in 'Building' started by dunny1234, 20 Nov 2011.

  1. dunny1234

    dunny1234

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    Hi,

    I'm about to lay a concrete slab 10m x 6m, and 100mm thick. I'll be using steel mesh, but do i need to install movement joints? If so, whats the best way of doing it? Thanks in advance
     
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  3. ^woody^

    ^woody^

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    Movement, contraction or construction joints?

    Do you expect the slab to move or contract?
     
  4. dunny1234

    dunny1234

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    it'll be on good ground and sub base, but wont it expand and contract throughout the year with temp changes?

    do you think i need them?
     
  5. Alastairreid

    Alastairreid

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    Yes!

    Read Here.
     
  6. dunny1234

    dunny1234

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    Thanks for the info. I really want to pour the slab in one go, whats the best way of doing this? I've noticed a lot of people use wood, is it just a case of postioning lengths of plywood in my form work split the slab in sections and securing, and then pour the concrete?
     
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  8. themiddleagedun

    themiddleagedun

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    I wouldn't bother myself. Its not a large area, and will only use 6m of concrete.
    If it's poured between walls I'd use expansion board around the edges (12mm fibreboard or similar) otherwise crack on. (no pun intended)
     
  9. Norcon

    Norcon

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    Pour in one go and then saw a single cut with a diamond blade after wards.
    I'd recommend adding fibre if its an outside pour.
    Some concretes are more suspectible to cracking than others.
    Largest area we did without joints was 60m x 30m and it never cracked.
     
  10. ^woody^

    ^woody^

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    What was that for?
     
  11. Norcon

    Norcon

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    That was on a 500 cow dairy farm. About 1000cu/m of concrete went into that one.
    1.2 million gallons of slurry storage capacity with 3m walls.
    It also got a lift in the middle after heavy rain shortly after it was completed of about 150mm cracking the center walls though the floor never failed even though it had flexed considerably.
    It went back down like the titanic when we allowed it too flood. Was only a few feet of water on the outside. :mrgreen:
     
  12. dunny1234

    dunny1234

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    Thanks for the advice all. I'm going to leave the expansion/movement joints. Next is dig the footings and prepare slab, thanks again
     
  13. DIYnot Local

    DIYnot Local

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    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

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