Marmox Boards on the Floor andUFH

[Ziggy1979]

Hi Everyone

DIying my first bathroom with a level access marmox shower tray and boards for floors and walls so in at the deep end! I am using 25mm WBP ply screwed at 200mm with noggins at 600mm (ply edges) - we only need 2 8x4 sheets and one cut down 8x1 (width of room pretty much 2400mm plus a little for expansion).

I read on previous posts that marmox boards need to be set in a flexible tile adhesive on the floor. But then I read that marmox allows for simply screwing them down to wooden subfloors. I called marmox tech and they said that laying onto a new ply floor is just about the only situation they recommend simply screwing down with dowels as the floor will be totally flat. Do you guys agree with this or should I still use flexible adhesive?

I think the floor is slightly out of level (6mm max across 2400mm) should I pack the ply or level with SLC before (or after) the UFH/Marmox go down?

I'll also be fitting UFH, then SLC and then marble tiles. Can you please recommend the best UFH and SLC for the job? Id like to use 150W mats (marmox confirmed this is ok for boards and shower tray) but devimat only makes 100W "suitable for timber" anything higher is for concrete. Will a concrete 150W Devi mat be ok or should I buya different brands 150W?

Thank you all so much for your help. Im taking pics so if it doesn't all (embarrassingly) fall apart I will upload them all when finished.
🙂

 

[Qwerty]

Welcome

Personally I would recommend you still use adhesive under the boards.
SLC after UFH is down to take out any difference in floor.
There are many choices of UFH & SLC and you will get a lot of different answers. I personally use Warmup kits and Mapei Ultraplan Renovation Screed.
A 150w mat is a 150w mat. I've never used Devi so I can't comment but just make sure it's all fitted as per instructions or risk making any warranty null & void.

 

[One Day]

I'd say a 150w mat is not always like every other 150w mat.
My trials and experiences with different mats in the effort to save or make a few quid or try out a fancy thermostat has led me to stick solely with Devi.
there's just nothing better made or easier to install in my opinion.

 

[Dougs Third Go]

surely the marmox boards will stop the heat transferring to the ply?

 

[Qwerty]

I'd say a 150w mat is not always like every other 150w mat.
My trials and experiences with different mats in the effort to save or make a few quid or try out a fancy thermostat has led me to stick solely with Devi.
there's just nothing better made or easier to install in my opinion.

I have found differences in thermostats yes, but not mats. Could be wrong though.

 

[SJPurdy]

There are differences in the mats between manufacturers: Some of the cheaper ones have much thicker wires so you need to use lots more expensive adhesive or SLC. Also some are tacky over the whole mat for sticking down to the floor whereas others have lines of double sided tape that you have to peel back as you lay to stick them down to the floor.

 

[Ziggy1979]

Thanks a lot everyone!

I spoke with Devi tech dept and they said that the 150W mats are ok to use over the ply/marmox and would not invalidate any warranty despite the "for concrete" description. He also said it was ok for use in the shower tray as long as marmox said it was ok (they did but I think others, like Impey only allow up to 100W on their trays). Devi tech also said that there is no need for waterproofing/tanking over the SLC as the mats are fully waterproof (something about EU Regs saying how they have to use certain materials, etc to ensure fully waterproof). Finally he also said not to start or finish the mat inside the tray and that no decoupling membrane was needed over the SLC. Phew...just thought I'd put that on there in case it helps someone else! 🙂

Now to more questions... 😉

Im thinking of using a 20mm trowel and Keraquick to fix the boards to the (3) brick walls. They are really flat and we don't have much space so would rather not batten or dot and dab. Have any of you guys installed them like this before? Any tips, problems, etc?

Also, I'm thinking of building a little half wall perpendicular to the brick wall, along the bottom of the shower (900mm) with a glass screen above this to separate the sink from the shower rather than have a glass screen all the way to the floor as then you'd see the side of the sink, drawers, etc (again not much space). Can I build this half wall using 2x2 (to save space) or do I really need to use 2x4?

Thanks again!

 

[Dougs Third Go]

Thanks a lot everyone!

I spoke with Devi tech dept and they said that the 150W mats are ok to use over the ply/marmox and would not invalidate any warranty despite the "for concrete" description. He also said it was ok for use in the shower tray as long as marmox said it was ok (they did but I think others, like Impey only allow up to 100W on their trays). Devi tech also said that there is no need for waterproofing/tanking over the SLC as the mats are fully waterproof (something about EU Regs saying how they have to use certain materials, etc to ensure fully waterproof). Finally he also said not to start or finish the mat inside the tray and that no decoupling membrane was needed over the SLC. Phew...just thought I'd put that on there in case it helps someone else! 🙂

Now to more questions... 😉

Im thinking of using a 20mm trowel and Keraquick to fix the boards to the (3) brick walls. They are really flat and we don't have much space so would rather not batten or dot and dab. Have any of you guys installed them like this before? Any tips, problems, etc?

Also, I'm thinking of building a little half wall perpendicular to the brick wall, along the bottom of the shower (900mm) with a glass screen above this to separate the sink from the shower rather than have a glass screen all the way to the floor as then you'd see the side of the sink, drawers, etc (again not much space). Can I build this half wall using 2x2 (to save space) or do I really need to use 2x4?

Thanks again!

err, devi mats come on a 500mm mesh ​roll, how can a mesh be waterproof?

 

[thompsonbrown]

Thanks a lot everyone!

I spoke with Devi tech dept and they said that the 150W mats are ok to use over the ply/marmox and would not invalidate any warranty despite the "for concrete" description. He also said it was ok for use in the shower tray as long as marmox said it was ok (they did but I think others, like Impey only allow up to 100W on their trays). Devi tech also said that there is no need for waterproofing/tanking over the SLC as the mats are fully waterproof (something about EU Regs saying how they have to use certain materials, etc to ensure fully waterproof). Finally he also said not to start or finish the mat inside the tray and that no decoupling membrane was needed over the SLC. Phew...just thought I'd put that on there in case it helps someone else! 🙂

Now to more questions... 😉

Im thinking of using a 20mm trowel and Keraquick to fix the boards to the (3) brick walls. They are really flat and we don't have much space so would rather not batten or dot and dab. Have any of you guys installed them like this before? Any tips, problems, etc?

Also, I'm thinking of building a little half wall perpendicular to the brick wall, along the bottom of the shower (900mm) with a glass screen above this to separate the sink from the shower rather than have a glass screen all the way to the floor as then you'd see the side of the sink, drawers, etc (again not much space). Can I build this half wall using 2x2 (to save space) or do I really need to use 2x4?

Thanks again!

Impey allow you to use 150w UFH on there new tanking membrane, 100w on there old tile safe membrane
All electrical UFH is waterproof Devi Tech probably meant that you dont have to use slc to cover wire.
Personally I would, Helps disperse heat and takes away the chances of damaging cable with trowel when tiling.
Unless its a weight problem, if your walls are really flat and your tight on space, you could always use a tanking kit insted of marmox boards. If you are using the boards, I would use adhesive and also mechanically fix to wall.
Don't see any problem with using 2x2 for wall below glass screen

 

[Tabby Cranks]

I'm gonna trial a complete schluter system now they have the Ditra Heat.

 

[Ziggy1979]

Hi Everyone
After a couple of weeks worth of building, etc distraction I'll finally be starting the bathroom this week!


Thanks for all your help and advice so far!


I thought of buying the 2500mm 10mm & 12.5mm Marmox boards as room is approx 2500mm tall and floor is approx 2800x2400. Are the 2500mm boards hard to use? Would u recommend using the 1250mm ones instead?


Also, do I need to leave any expansion joints where the wall boards meet the floor/ceiling and where the floor boards meet the walls?


Finally floor is out of level by approx 10mm across the 2400mm width of the room. Is it ok/possible to level this by using more tile adhesive under the marmox board? They are going over 25mm WBP Ply (thought of using Keraquick without added latex).


Thank u all so much again!!! 🙂


Sent from my iPhone

 

[Qwerty]

Use the 1250 boards, yes do incorporate expansion joints and use SLC to level after laying the UFH.

 

[Ziggy1979]

Hi Everyone

ive finally dot and dabbed the boards. It was a lot easier and less intimidating than I thought it would be...thank god!

I now need to drill through and screw with metal washers (instead of the plastic hammer in dowels). I think it's a dumb question but do I use normal red or brown rawl plugs which won't go much deeper than the keraquick dabs or should I use other fixings that go deep into the brick walls behind?

thanks again for your help!

 

[Qwerty]

Normal rawl type plugs just fine. Drill through further to allow for the depth as you say. The rawl plugs should be into the wall though for a solid fixing. Did you pre drill the board prior to spot fixing?

 

[Ziggy1979]

Thanks PTT

I punched 5 holes with a screw driver and put large dots over them. I also put dabs all over the edges and many more in the middle. Tbh it looked like overkill but the boards are 12 mm and I was worried about them flexing if there wasn't enough adhesive (did seem to use a lot of Keraquick though (and its pricey).

Ok...so shall I drill a bigger hole (eg 8mm) in the marmox/dot/dab and then a 6mm hole (for the rawl plug) in the brick? I've bought 50mm long stainless turbo ultras so hopefully they'll be long enough to reach.

For the bath panel, can I build a frame out of 2x1 and fix 12 mm boards to this? Should/can the bath sit on the frame? If not, how should I secure it? The reason for 2x1 is so that the tiled finish is flush with the edge of the bath. I have to make a tiled panel for the top end and one side of the bath with access for the taps/trap.

thanks again!

 

[Qwerty]

No, just use a 6mm bit to drill through both but you just need to ensure the rawl plug is in the wall securely.
As for the frame, I would try to use cls if it will allow. Fix frame securely to walls and floor (can even use a mastic type adhesive across the top where it adjoins the bath.) Make sure it is a solid rigid frame for the marmox to fix to. You can use thinner marmox here if you like. Two vertical uprights within the frame should suffice. I often use keku or magnetic fixings for hidden panels with a neat bead of Silicon instead of grout.

 

[Ziggy1979]

Thanks again PTT 🙂

For the CLS frame, what sized timber is the minimum I can safely get away with? The edge of the bath isn't very wide and I think the tiles (marble) will be about 15mm so I'm not sure ill be able to use 3x2.

for the hidden panels, do u fix the keku/magnets to the back of the marmox board? If so, can't the screw rip off the marmox when pulling the panel out?

Thanks! 🙂

 

[Qwerty]

Basically you need to use the biggest size you can get away with under there. I use 3x2 if I can. I screw through from the face of the marmox using a washer to spread the load but use screws that screw into the plastic holes of the keku fixings. Once tiled over on the front it is a very solid fixing!

 

[Ajax123]

You have a floor area approximately 2.4x3m = 7.2m2 based on a 100w/m2 mat you will get a heat output of just 720w per hour. That dies not allow for any downward heat loss. You need to calculate the rooms heat loss to see if 720w/h will overcome the heat loss. If the heat loss is more than 720 your room will never warm up ad your electricity bill will be huge.