Concrete Slab expansion joint

Discussion in 'Builders' Talk' started by Kevin Gilmour, Nov 6, 2022.

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Is the expansion gap required ?

  1. Yes

    0 vote(s)
    0.0%
  2. No

    1 vote(s)
    100.0%
  1. Kevin Gilmour

    Kevin Gilmour New Member

    Looking for a bit of advice please.

    I’m about to pour a concrete slab for a stand-alone raised patio which is getting tiled with porcelain tiles 600mm x 900mm. The slab is just under 6m by 4m and 6” thick. However all around the edge of the slab will be a box section of the concrete reinforced with rebar and the whole slab will have mesh rebar reinforced. With this size of slab, coupled with the rebar, finished with porcelain tiles, should I put an expansion joint in at all ? The sun base is very well compacted and the patio is south facing so does get full sun all day long in summer.

    Thanks in advance for any advice, Kevin.
     
  2. qwas123

    qwas123 Screwfix Select

    There are calc's for prepping and pouring slabs, and there's rule of thumb for small time concrete contractors.
    Why not give johnbridge.com a go - you wont regret it.
     
  3. Hausfix

    Hausfix Screwfix Select

    Theoretically, a 150mm thick slab should have an expansion gap every 5m for a large area, (this figure is from my memory, so best check to be sure)
    But, in this case, expansion wouldn’t be restricted by any forces outside of the 6x4m single slab.
    I’d imagine if an expansion gap within this slab were to be present, it wouldn’t be long before cracks would appear in any ceramic tiles laid over this gap..
    I would suggest that you lay the tiles on a product called Ditramat, which will allow the concrete substrate to move without affecting the tiles.
     
    Last edited: Nov 6, 2022

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