Suspended Timber Substrate For Wetroom? - Tile Advice

[BigSid]

Hi,

New to the site, but been lurking for a while and I'm after a bit of advice about timber floors. I'm in the process of converting my bathroom into a wetroom. It's a first floor bathroom with a timber floor, approx 3m x 1.7m with joists span the shorter distance. My house is a bit old and wonky, so I'm ripping up the entire bathroom floor (as it slopes towards the door) and levelling it out by battening the tops of the joists.

I've bought 18mm T&G spruce floorboards to put down and sheets of 12mm WBP ply to overlay, on top of that will go an Impey Waterguard tanking membrane and then tiles.

However, the wetroom tray I bought is the Impey Aqua Dec Easy Fit and it's 22mm thick, so I need to put something 8mm thick under it to bring it up to the level of the new floor (18mm T&G + 12mm ply), but you wouldn't believe how hard it is to find something suitable that is 8mm. Ply is like 5, 9.5 or 12. I did look at using 4mm Marmox backer boards doubled up, but the only place I could find them would only sell me 10 minimum and I'd only need 4...

I'm wondering now though, whether I should get shut of the T&G and ply and get Wickes 22mm p5 moisture resistant chipboard instead. Thoughts?

Thanks

 

[Old Mod]

Hi and welcome to the forum!

Ditch the ply and use 6mm Hardibacker boards, glued and screwed.
that'll come to 24mm that'll be manageable.

 

[Old Mod]

Or put sufficient noggins in ur joists to screw 18 ply at 300 centres.
Use Ditra25 decoupler over the top of ply
Tape and joint Ditra with Kerdi Keba 125mm with Kerdi Coll adhesive,
U can also form a skirting with the Kerdi Keba 75mm up wall 50mm overlap on to Ditra.
This will form a completely waterproof floor at same time if fitted correctly.
The Ditra is approx 4-5mm fitted, that'll come level with hour tray.
But it'll rely on your joists forming a deflection free substrate.

 

[BigSid]

Thanks for the replies. Is the hardiebacker board that good? Would it do a better job than 12mm ply screwed/glued to 18mm t&g floor boards?

As for the tanking kit, I looked at the Schluter stuff, but found it to be a bit out of my price range, plus I liked the idea of the impey being self adhesive so I didn't need to use twice as much tile addy. From looking at the Schluter products, I got the impression they were more for much larger or commercial applications, hence the reassuringly expensive price.

 

[Old Mod]

Hardibacker will not expand and contract with heat or moisture.
IT IS NOT WATERPROOF!
It must be tanked.
Ply will deform if it is subject to heat/cold/moisture, for these reasons alone Hardibacker is superior, yes.
Schluter are marketed at both domestic and commercial installations, it's reassuringly expensive because it is designed for ease of use and it's actually one of the best out there.
It's the only company to my knowledge that actually makes a shower former for the uk market specifically, so that it can be fitted in to 18mm ply.

 

[macten]

Was speaking to the NoMorePly rep and he said NMP with their primer and joints siliconed makes for a perfectly waterproof floor in a wet room. Don't know how true that is but I told him I wouldn't feel confident doing a wetroom like that.

 

[macten]

James Hardie do a 19mm and 22mm product called Hardiefloor that can go straight on the joists and acts as a structural floor and tile backer board in one go. Going to use it in my own ensuite if I ever get round to finishing it - been 5 years so far!

 

[BigSid]

That does sound a bit dubious, if NMP is a cement based board, I can't imagine that it's waterproof... granted it won't break down in the presence of moisture, but cement is pourous and therefore water will gradually seep through it I would have thought.

Thanks for all the replies, although I've already purchased a lot of my materials, so it looks like I'll be going with 18mm T&G with the joints glued, with 12mm WBP ply on top, then the Impey Waterguard system, then WarmUp UFH, then a thin bed of FLC (to protect the heating mat) then BAL Max Flex Fibre and then tiles (still can't decide which ones though). I'll put a sheet of 9.5mm WBP ply under the Aqua Dec to bring the height more or less level with the surround floor (it'll be 1.5mm proud but I can lose that in the FLC/addy).

Spoke to both Impey and WarmUp tech support about doing ply, tank, ufh, flc, addy, tiles and both seemed happy that would be perfectly fine.

If I hadn't already purchased the materials, I would have gone the cement backer board route for the floor too (I've got AquaPanel for the walls around the shower), but I'm not too concerned about the ply in terms of moisture, because it shouldn't get wet at all, unless something's gone wrong with the tanking membrane.

Cheers

 

[BigSid]

Was speaking to the NoMorePly rep and he said NMP with their primer and joints siliconed makes for a perfectly waterproof floor in a wet room. Don't know how true that is but I told him I wouldn't feel confident doing a wetroom like that.

Ah, missed the bit about the primer. If their primer is more like one of those paint on membranes, a bit like the BAL WP1 stuff then that would make more sense. Although I'd still be a bit iffy about the edges of the floor, surely you'd want some tape for the floor/wall joints rather than just sealant?

 

[macten]

Their primer is just an SBR but it has to be their primer for a wetroom guarantee and he might have said the joints need sealing with their mega strength glue and not silicone - can't remember now.
I always go belt and braces using tried and tested methods/materials for building a wetroom - primed cement boards would always leave me worrying despite the company's claim otherwise.

 

[BigSid]

When I'm done I'll get some pics posted

 

[thompsonbrown]

I know you have had some good advice in previous posts but why not just replace your floor with 22mm wayrock, egger "chipboard" this is the same depth as your Impey former.

 

[BigSid]

Promised some photos, so for those who are interested here is the progress so far...


Ripping out the old bathroom...

Ripping up the old floorboards...

Levelling the joists with battens...

Deck to provide support for the Impey wet room tray...

T&G floorboards down, glued and screwed...

Impey deck down...

Floor over boarded with 12mm WBP ply...

Ceiling plaster boarded and IP65 LED spots in.

 

[Chalker]

Would have done it diferently, but your making a good job so far.

 

[BigSid]

Would have done it diferently, but your making a good job so far.

Thanks, but differently how? I will post more pics as things progress.