Wet room advice and questions

[Garreth]

Hi Guys and Girls

Im over from the electrical forum normally giving electrical advise. I looking for some advice and to gain some knowledge

Im looking at installing a wet room with underfloor heating mat and then tilling the full room

Ive had a look at existing posts on here but I am confused by a few points so hope that you fine people will help straiten a few things out.

I will try and keep this as clear as I can

Starting at the top of the joists i have 22mm chipboard floor on top of that.

my thoughts are having a 30mm wet room shower tray former on the floor sat on top of the joists.

then putting 10mm insulation boards onto of the chipboard and screwing it all down

then tanking the room with a tanking kit the rest of the floor will be 2mm higher though

then putting a electric heating mat down (does this go over the shower former or just the surrounding bathroom area floor)

this is where I'm a bit confused.

Do i need to use a self leveling screed to encase the underfloor heating mat ?

if i do then it will flow into the shower area and former and change the level

then tile on top of this

my worries is that if i have the heating mat/screed in the bathroom this will then be higher than the shower tray former so there will be a step down into the shower I want the floor to be one level.

I am looking for advice from those in the know

Cheers

Garreth

 

[Flintstone]

Hello! 30mm tray onto joists, well supported, then 6mm insulation board glued and screwed onto your chipboard flooring, then your wires and 4mm of levelling compound to make it all flush. Then your waterproofing then tile.

 

[Garreth]

Localtiler thanks for your reply.

so 30mm tray and 6mm insulation on the 22mm floorboards which means the tray is 30mm and the floor is 28mm

when you say waterproofing what do you mean is that on top of the heating mat and compound

how do you stop the levelling compound going into the shower tray and levelling that off ?

I'm looking at insulation boards that are waterproof and I right in thinking that you then seal the joints in-between the boards and the edge of the boards and shower former with tanking tape ?

then underfloor heating mat on that followed by levelling compound then the tiles on top of that

 

[Flintstone]

If you raise the tray up a few mm from joist height you will have enough height on the floor to level up to the tray flush. If your using water proof boards through then yes just seal all joints

 

[Garreth]

If you raise the tray up a few mm from joist height you will have enough height on the floor to level up to the tray flush. If your using water proof boards through then yes just seal all joints

so tray in and insulation boards and the joints sealed with tanking kit

heating mat and living screed fitted in the bathroom and then tiling on top

what i cannot understand is that with the heating mat and leveling compound in the main bathroom this means that the bathroom floor will be 4/6mm higher than the shower tray. how do you tile the shower tray and bathroom so that the floor is one level ?

secondly how do you stop the leveling compound flowing into the shower tray and leveling the shower tray off ? if you put a batten along the edge you will end up with a small step in the floor levels. how do you get the same tile hight ?

or is that the idea and you build the edge of the tile up so it is a steeper slope into the shower than the shower base

 

[Time's Ran Out]

Any extra fall you can get from outside the tray area to the outlet only helps the flow away.

 

[Flintstone]

Garreth, think about it, 22mm chip board + 6mm insulation + 4mm wires and slc = 32mm. Your tray is 30mm. You need to make supports anyway under the tray so just raise it up a few mm and when you pour your leveller, pour enough so it goes flush to the tray not into the tray.

 

[Garreth]

Garreth, think about it, 22mm chip board + 6mm insulation + 4mm wires and slc = 32mm. Your tray is 30mm. You need to make supports anyway under the tray so just raise it up a few mm and when you pour your leveller, pour enough so it goes flush to the tray not into the tray.

I get that but i need to tank the room as its a wet room so as I understand it the tray goes in then the insulation board tank the whole floor and walls then the underfloor mat and then the SLC so this will then be above the level of the shower tray

if i put some timber down as a temporary dam along the edge of the shower tray this will then leave a very small step

 

[Flintstone]

Is it me or you that’s not quite getting it here?
You can tank after slc has gone down, here’s one I did recently virtually the same as your wanting to do. Tanking adds no build up

 

[Garreth]

So you can lay the underfloor heating mat then the slc then tank over the whole lot ?

I was under the impression that the underfloor heating couldn't go underneath the tanking and in fact the heating mat has to sit on top of the tanking system then the slc to encase the heating mat and then the tiles

 

[Flintstone]

There was some debate about the correct way to do it on here a while ago, but yes with what you are doing, tank on top of the slc as per photo. Once it’s fully dry ofcourse

 

[Garreth]

Thanks for your advice Localtiler. I am apprehensive about applying the tanking on top of the slc I'm thinking that the heat from the matting will warm and damage the tanking solution. As I say I was always under the impression that it should go tanking, then heat mat, then screed, then tiles.

if I do it that way then I will have to make a dam on the line of the shower tray to stop the slc flowing onto the shower tray. I am worried this will then make a step and different levels in the floor which I will struggle to keep the floor levels the same.

the next question I have is I have to replace the current chipboard floorboards as the current ones are rotten. They are 22mm currently but I'm planning to use thinner 18mm ones and then insulation boards to make the level up and insulate the floor.

The question is should I use waterproof plywood for the floor or would normal chipboard be ok/ sensible to use? in theory they shouldn't get wet as the waterproof insulation and tanking is forming a waterproof barrier