Can i lay plywood instead of chipboard or do i need both???

[suggett1976]

Ok

I am laying a tiled floor in my bathroom.

Currently there is a chipboard floor layed onto the joistes. The chipboard has had it so needs replacing.

Now can i lay a 18mm plywood straigth onto the joists and then tile, or do i need to lay 13mm chipboard then the 18mm plywood, then tile.

I was hoping to do away with the chipboard so that i eliminate a step into the bathroom.

please email me at [email protected]

 

[Richard C]

The best possible thing you can do is to remove the chipboard & replace it with WBP plywood painted with a sealing primer on the back; this is by far the best base for a suspended tiled floor. 18mm is usually sufficient in most cases but if the floor flexes unduly, use 25mm thick, screwed to the joists at 150-200mm centres max. Make sure any joins in the ply run down the centre line of a joist & insert noggins between the joists to support any joins across the joists.

Use only a quality trade, flexible adhesive & grout for the tiles. Most don’t require any surface preparation but check & follow the manufacturer’s instruction regarding this. Read the tiling sticky & the archive tiling posts for more information to avoid you making any mistakes.

It’s not normal to reply to posts via personal E mail.

 

[suggett1976]

Ecellent. Thank you.

When you say to seal the underside, do you mean with a PVA glue of some sort.

 

[Richard C]

The purpose of priming the underside & edges of the ply is to seal it to avoid any moisture absorption that could cause the plywood to warp, cracking the tiles. You need a waterproof, SBR based sealer such as;
http://www.bal-adhesives.co.uk/products/bond-sbr

Do not use PVA, its water soluble & totally unsuitable. BAL recommend priming the underside but, in reality, many don’t bother & anything that will act as a barrier to prevent moisture absorption will do it, even old oil based paint.