Substrate confusion...

[trevster]

Hi Guys,

I keep ending up on this forum during my ever more confusing research into my (ever more complicated) bathroom renovation.
I was hoping that i might be able to get some direct opinions on the floor and wall construction of my bathroom.

I have a ground floor bathroom (approx 3.6 x 1.5m) with a concrete floor. (It's been made from joining a tiny bathroom and a small hallway, and is being plumbed and finished basically from scratch.) I will be building up the height of the floor by around 50 or 60mm to bring it in line with other rooms. I have been advised to do this using a layer of cellotex followed by a floating chipboard floor. One thing i've learned from here already is that tiling onto chipboard is a big no no (unless you are a qualified structural engineer, it seems). So i'm thinking of going over the chipboard floor with 12mm wbp ply. Does this seem like a sensible idea? Is there a better way of going about it? Thicker ply with no chipboard? Chipboard with 6mm Hardibacker? Will a floating floor on cellotex be rigid enough to take tiles?

The bathroom will consist of wall hung/back to wall toilet/bath/sink lined up against one wall, which will be studded out by 150mm to a height of 1200mm, thus concealing all the plumbing. The bath will have wall mounted taps and a concealed shower valve over it. The stud wall will be finished in 100 or 150mm sq tiles, and the top section of the wall will be completely covered in mosaic tiles.

This weekend i'll be first fixing the studding (which will be pressure treated timber with some marine ply reinforcement), i'm also planning on battening out the top section the the wall by around 20mm, so that i can incorporate some insulation, and also so i can true up the surface and bring it all into line.

So soon i'll have a whole walls worth of timber waiting to be boarded over and tiled, but i can't decide what to use. I have been thinking about using Hardibacker, but i've just been reading about how it is water resistant, but will not necessarily prevent water seeping through it, which has made me think twice. If it's more important for me to waterproof the area, will i need to tank it? And if so, wouldn't it be a waste of money to use anything more then standard plasterboard?

Advice on any of these issues would be much appreciated...

regards,

Trev

 

[Rizzle from the Portizzle]

screed the floor up to hight required with sand and cemment on the walls if you are going to tank them plaster board will do

 

[DHTiling]

You will be creating a floating floor , big no no for tiling too.

Either screed it or batten out and fix wood substrate to them.

 

[bugs183]

I prefer to use marmox boarding now if possible. It's waterproof, unlike Hardibacker (water resistant, i'm told), and it really easy to work with. so no need to prime or tank, just use water proof tape on the joints.
An unbonded floor as said is a no no, so many companies say it's ok to tile onto unbonded floors but this is wrong, as us tilers keep saying!!
So screed... or if want a quick flat solution, use 50 or 60mm Marmox boards, they'll just cut and drop into the floor, stick down with adhesive, no faffing. May need to use some levelling compound here and there. It may cost a bit more, but it would be a lovely quick solution.
I scour the internet for prices, but so far can't find anyone to beat Insulation Express, and they are great to deal with.

 

[trevster]

Thanks so much for the replies guys.
I had a feeling that a floating floor may cause problems. If i were to batten out the floor, what spacings would you recommend (i'll be doing the same in my 3.5 x 3.5m kitchen soon too), and how important is it to get a good fix with the battens into the concrete floor - i'm trying to keep hammer drilling to an absolute minimum for the benefit of my neighbors (and wife)...
Thanks Bugs for the suggestion of Marmox, it looks just the ticket, not sure if i can stretch to using it on the floor, but certainly on the walls. Looks like i can forget about battening out the upper section too. I was about to ask whether it can be attached dot and dab style, but then i watched their interesting video on the subject. I'd be interested to hear any recommendation you may have regarding adhesive for this and whether the nailable plugs they show are a good idea or not - i've never seen them before.
I was looking at using insulation express for the other stuff actually, glad to hear they're good to deal with.
Thanks again for the advice.