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Fixing A Wall Plate To Thermalite Wall?

Discussion in 'Building' started by Spuggy, 15 Dec 2008.

  1. Spuggy

    Spuggy

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    Hi All,

    Would be grateful for a second opinion on advice given to me by architect this afternoon!

    Currently building a large two storey extension to the back of our house. The builder left holes in the inner blockwork skin at 400mm centres for the first floor joists to sit into. Unfortunately, the time has come for me to put the joists in and it turns out the holes are over 40mm too low to pick up level of existing first floors.

    I called architect for advice as I thought I'd have to cut 40mm out the top of each hole to pack joists up. However, he says I can just fix a timber wall plate to the face of the thermalite wall and hang the joists off hangers.

    Is this possible, would the soft blocks and fixings take the weight, what fixings would I need?

    Many thanks for any advice or alternatives.

    Cheers, Paul.
     
  2. ^woody^

    ^woody^

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    Possible, but a crapp suggestion - why buy more timber and fixings? Is the Architect paying for them :rolleyes:

    Use a saw to lengthen the slots upwards, then pack up the joists on some timber, tiles - or the bit of block you have cut out of the top.
     
  3. Spuggy

    Spuggy

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    I thought the suggestion was a bit crapp myself, that's why I came on here to ask first!

    Thanks Woody!
     
  4. stuart45

    stuart45

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    When hangers are built in to the wall there is weight on top of them. Sitting on a plate there would be nothing to stop them bending upwards.
     
  5. ^woody^

    ^woody^

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    That is, unless they are speedy timber hangers ;)
     
  6. regsmyth

    regsmyth

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    Personally I'd be a bit concerned about the load bearing surface of the raised slot.
    If the joists were sitting on the flat top of the blocks I guess it's ok, but to fit hand cut little bits into holes and resting the joist end on that seems a bit naff. The load on that little bit when three or four people happen to be standing on that bit of floor is going to be quite high enough to crush any irregularities on the bit of cut block, and give you a bouncy floor.
    I think a timber on the surface is probably better.
    Or how about lengthening the slots upwards then filling up to the right level with concrete and a bit of slate on top.
     
  7. mater

    mater

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    why not use hangers that you can cut into the wall, but fill your holes first. you can get these at most builders merchants
     
  8. ^woody^

    ^woody^

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    Don't forget the rest of the wall below!

    The bit of block cut out the top and put in the bottom will perform exactly like the rest of the wall
     
  9. regsmyth

    regsmyth

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    I dont agree - if the bit that gets puts back in is a bit wonky, or out of square etc, the bearing surface could actually be tiny, so it will crush when the joist is heavily loaded. It might not completely disintegrate, or turn to dust, or crack right through - but it could cause a bouncy joist end. Not so if the joists are resting on the flat top of an uncut block.
     
  10. ^woody^

    ^woody^

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    Well normally the bit would be set in mortar and the flat surface uppermost, or smoothed off with mortar or a packer of slate or fibre cement board - whatever is available.

    The thing is not to make a meal of this and buy more stuff unnecessarily.

    The OP can mark the wall with a datum top or bottom of the joist or fit a lath and work to that
     
  11. karlosmaximos

    karlosmaximos

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    if the are thermalite,the why not just cut some new holes entirely and fill in th old ones?
     
  12. ModernMaterials

    ModernMaterials

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    Cus that sounds like making work unnecessarily when Woody has already pointed out the way to go :)

    No one bats an eyelid when RSJs are bedded on to bits of brick/ slate/ compo so why is it gonna be a problem to mortar in a small piece of block into a wall of the same material

    It will be cheaper and stronger than the wall plate and joist hangers option.
     
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