Tiling on kitchen (Polystenre and interlocking floorboards)

15 Apr 2010
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United Kingdom
I want to tile the kitchen floor about 7sqm.

Current Kitchen floor: Interlocked chipboard boards, which if removed, will show clear transparent plastic sheet and then 2" white polystyere. Below that is something solid probably concrete...

This is a 80s built Barrats flat.

The builder gave me two options for kitchen tiling.

(1) Remove chipboard friom the kitchen and replace with 18mm plyboard. and tile on wood. So the plyboard rests ontop of the polystyrene.

(2) remove chipboard, polystyrene and fill area with cement or concrete and then tiles on it.


I have a number of concerns, I don't know too much about the pipework below. If I decide to go for concreting the kitchen floor. how can I ensure that the pipework can be repaired? Can I box the pipework and lay concrete ontop of it?

Can the polystyrene which I suspect provides insulation, be replaced with something equivalent?. The polystyrne can be sqeezed, so don't like the idea of it....
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If you can accomodate a little bit more height on the floor you can overboard the chipboard with a quality plywood layer of around 12mm nailed at 150mm centres with 25mm ring nails.
Even with a suspended timber floor (over joists), 18mm WBP is marginal for use in a high load/use area such as a kitchen; IMO you need 22mm – 25mm depending on joist size/pitch/span. Have you got any joists resting on the slab or is it just boarded over the insulation? If you have no joists, it’s a floating floor which can be a real problem when tiling &, depending on construction, it may not be suitable unless you provide support from the slab. You can do this either with your tilers option 2 or by installing timber joists supported by the slab. Over boarding the chip (which I wouldn’t do anyway) may still not be enough; if there is too much flex in the floor, the tiles will fail.

If the pipe work is checked & replaced where necessary with no push fit or compression joints, over concreting is OK as long as the pipes are protected. Pipes can also be run in a duct backfilled with Vermiculite before concreting but the floor will still have to be dug up in the event of a problem; this is not a common problem except in very old houses.
Thank you for the replies....

Richard C asks>> Have you got any joists resting on the slab or is it just boarded over the insulation?

There are no joists. They have rested the interlocking chipboard on top of the polystyrene....
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You have a floating floor & a problem as far as tiling goes but I think your instinct already threw up suspicions about that. As you’re in a flat, joists supported off the slab with insulation between would be a better option than infilling with concrete but you will be taking a huge risk if you tile without supporting the floor & tying it back to the concrete slab.

Here is a similar thread;
A search of the tiling forum will throw up several others.
Go for a high quality vinyl like Karndean or Amtico. Overboard floor with 6mm ply.

Having lived with both vinyl and ceramic/stone tiles in both Kitchens and bathrooms- viny is a better product due to the grout joints in ceramic tiles forever needing cleaning and being recessed and porus, catching every possible bit of dirt.

Down to personal choice though but for me, the decision has been made for you due to your floor conditions.
I agree with bathsyle. Why make life difficult? Vinyl is warmer and more friendly to feet too.

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