What thickness ply?

28 Mar 2011
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United Kingdom
I am re-modeling our en suite and need to remove the 20mm chipboard because it's not level and I need to add longer soil pipe, so if the final finish is going to be 10-13 mm slate tiles on top of 4mm underfloor heating mat, what thickness ply would you use?

Many thanks

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bathroom chipboard swells when damp, so it may well have been 18mm when new.

If you care enough, seal the edges of your new WBP ply with varnish or paint after cutting. Wet edges will degrade it faster than a wet top (but seal the top as well if you can be bothered).
25mm WBP ply if you can afford the extra height. Makes a very solid floor.
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And fitting a few noggins to add support wouldn't go amiss either.

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