bathroom floor - which ply?

[edl123]

Hi,

I am building a raised platform in a bathroom which will then be tiled. Was thinking of using 18mm marine ply. Just wanted to check if this was either a) overkill, b) not enough or c) just about right.

Thanks for any help/advice you can give. The supporting joists will be 300mm apart by the way.

 

[JohnD]

WBP will be fine. Marine ply is more expensive but will usually have an attractive hardwood surface that you can stain and varnish if you want.

 

[edl123]

Thanks for the quick reply. wbp would save me a lot of time and money, as long as it is moisture resistant enough. will it need treating? if so, obviously i need to treat it with something that doesnt affect the tile adhesive.

 

[Richard C]

As JohnD said you don’t need marine ply, 18mm WBP will be fine; the adhesive is waterproof not moisture resistant. Support it well on 50mm wide timbers, every 300mm will be fine but I assume they are also supported by the floor. Screw (not nail) fix every 200mm, seal the back (non tile face) & exposed edges of the ply well with acrylic primer. Do not prime the tile face & use flexible cement powder adhesive & grout, do not use tub ready mix. What tiles are you laying? Are you tiling elsewhere in the room?

There are many things to catch you out particularly if you intend tiling a suspended timber floor. I would advise you read the Tiling Sticky & Forum Archive posts before doing any more work or buying materials, it could prevent you making disastrous & potentially expensive mistakes. It’s important to use only quality trade tilling materials of the correct type for your tiles & tile base; cheapo own brand & DIY stuff is mostly crap. Post the Tiling Forum if you need any guidance.

 

[edl123]

Thanks for the advice. I am building the platform but will pay a tiler to do the tiling, as there is too much to go wrong otherwise.

The tiles will probably be a (fairly cheap) ceramic or porcelain tile (not stone). The raised platform is for the shower and toilet (its the only way of getting the waste in).

Tiles are also going onto the existing tiled floor and plaster walls.

 

[Richard C]

As I said, read the tiling sticky & forum archive posts so you get an understanding about what to do in wet areas & over suspended timber floors (what is the floor?) & what materials your tiler should be using. Be aware that even plaster in good condition has a maximum tile weight of 20kg/sqm including >4kg/sqm for the adhesive & grout; critical if you’re thinking of large format tiles. Any paint on the plaster can reduce that considerably & additional prep is usually required.

You wouldn’t believe the number of posts & sob stories we get on here as a result of tile failure due to poor preparation &/or incorrect/poor quality tiling materials being used. Choose your tiler very carefully, not all are what they say &, unbelievably, some can’t actually tile.

 

[edl123]

thanks that's all very helpful, will check the sticky too. The floor is mosaic tile direct onto concrete (possibly original floor over 100 years old)

The walls aren't in great condition, plaster is ok but has old lead paint which is a nightmare to get off. The reason I'm paying a tiler is precisely for the reasons you have stated. Unfortunately as with all trades you can't guarantee they know thier stuff, just have to rely on recommendations and some common sense.

 

[Richard C]

By all means post more detail about what your tiler intends by way of prep & materials on the Tiling Forum as you go & I will advise; it should at least give you peace of mind

 

[edl123]

cheers will do. Thanks agin.