Marmox or membrane for bathroom floor

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Hi all

I'm a DIYer and after some advice on finishing my bathroom floor. I know there are lots of threads like this but none seem to quite match my circumstances and I don't want to get this wrong by mixing up the advice.

The room is on the first floor above the (unheated) garage and is 3.9 by 2.6 metres. I'd like a waterproof floor, floor-level shower and electric underfloor heating (including in the shower area). I'll be using through-body porcelain tiles (well, the tiler will - I know my limits).

I've already removed all the old floorboards and sistered the original joists (2" by 6" at 16" centres) with identical C16 joists to try to minimise any deflection. I plan on placing solid insulation boards between the joists. The bulk of the plumbing is done.

The only thing I'm committed to is using a 1400mm x 900mm Tuff2 shower former (I've already cut a hole in the wall for the waste) but the rest is undecided.

My original plan was to lay 18mm WBP ply on the joists and then 6mm Marmox screwed through the ply to the joists. The UFH would then be laid on the Marmox and tiled over. This was when I thought I'd be using a Marmox shower former too. Since switching to the Tuff2, I'm wondering if I should membrane the entire floor having laid 22mm WBP ply over the joists.

If I opt for a membrane on the floor, could I still use Marmox on the walls and make a waterproof joint between the membrane and Marmox?

Any and all advice appreciated.

Cheers
Simon
 
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Ditra membrane for the floor..

The walls are they 400mm centre for studs...if so then yes...min 12mm boards for walls and waterproof joins for all.

The 22mm wbp...hope you primed the underside and edges so to stop moisture ingress,as you said it's a garage underneath so you will have moisture rising up thro although you have insulation between joists,it will creep thro and also the garage walls,what are these made off...light weight block/concrete block ect...is it single skin...double skin...render...
 
Ditra membrane for the floor..
Thanks. Is that something a reasonably competent DIYer could install properly?

The walls are they 400mm centre for studs...if so then yes...min 12mm boards for walls and waterproof joins for all.
The walls are bare brick at the moment. Will probably have a professional do the boarding so it'll either be studs or dot and dab as he sees fit. I'll mention the boards needing mechanical fixings through to the brick.

The 22mm wbp...hope you primed the underside and edges so to stop moisture ingress,as you said it's a garage underneath so you will have moisture rising up thro although you have insulation between joists,it will creep thro and also the garage walls,what are these made off...light weight block/concrete block ect...is it single skin...double skin...render...
The ply isn't down yet so I'll be sure to seal all the edges - thanks. Will 22mm be thick enough to tile on? I'm hoping, once the ply is screwed down, there'll be a lot less flex in the floor.

The garage and bathroom walls are double skin standard house bricks, 10mm cavity on the one exterior side, 50mm cavity front and back. No render.

Do I need to worry about moisture between the internal leaf and the boards?
 
Floor membranes are pretty easy to fix to your floors.
You will precut it into sections to fit the floor,then using a 3or4mm notched trowel apply your flexy adhesive to the floor then fix your matting onto it,you will do this in strips all over the floor area...patting in down with a grout float..

Either use ditra or durabase C1++ matting..these are...crack isolation and waterproofing matting...

The 22mm wbp ply will be fine,prime it underside and edges with sbr primer..screwed every 150mm

Walls probably quicker to dot/dab your maramox boards to it then drill/plug/screw your fixing thro it...tape all joins with fiba tape..

The above floor membranes will stop any moisture penetrating through and de bonding your floor adhesives...
 
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Your elect ufh will go ontop off your floor membrane then apply a latex based slc over the wires...either use a plastic trowel or piece off wood,so you don't damage the heating wires...

Always following mfr inst re:when and how much to turn your heating mats or wires on..

To much to early will cause..thermal shock and could blow/tent your floor tiles..
 
Thanks for your help and advice, tictic. I'm hoping to be putting it into practice soon; been installing the insulation today.
 

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