Hi there,
About to start work on the bathroom or rather a 4mx3m room that will have a shower cubicle in the corner, a sink and a WC.

Two of the walls are external and need replastering. Underneath is thick stone and rubble North Yorkshire 1700's building. One has a window, the other an unused fireplace that we want to reatin for aesthetics. The other two walls are a. standard plastered stone and the other b. tongue and groove floor to ceiling.

We are trying out Eden lime's lime/hemp/ perlite insulating plaster in one room and are tempted to use it in here for its breathability coupled with insulating properties - but only on the two external walls.
We thought to apply water resistant tongue and groove effect MDF to about 1.1m on all walls with tiles on the shower cubicles back (one of the inside walls). No problem on the two inside walls but on the two outside walls should we just forget the insulating plaster below 1.1m and use a bit of standard insulation between the batons that hold the MDF on or put stick to the insulating plaster and put the MDF on top?

Always twitchy about damp/breathability/interstitial condensation.

The shower will be a Mira 10.8 Sport max and the builder plans to put in an extractor fan in the ceiling.

Any help welcome!

All the best

John

Posted By: laikipia... the builder plans to put in an extractor fan in the ceiling.

What do they intend on installing and how will it be ducted?

Most extractor fans are just holes in the wall/ceiling.

On that note, what is the lighting? If recessed downlighters need to consider air leakage.

good advice thankyou. The manufacturers/retailers seem to say "yes" (http://www.theenglishpanellingcompany.co.uk/questions.shtml#eleven) while the users say "no". Does this "no" also apply to the green water resistant MDF. It's not going to be in direct contact with water just in the bathroom.

Why do you even want to use MDF? Use a cementitous backer board instead. Waterproof, strong, reasonably cheap.

You could use this:
http://www.medite-europe.com/products/medite-mr

I kept a bit in a bucket of water for 13 months and it seemed fine.

Posted By: the soutercan you recall if that was that the exterior grade ST?

No idea, I just got them to send me a sample.

So sensible materials for bathroom walls are:
Painted plaster (I already have some of this)
Tiles (I'd prefer to avoid this 'cos it's slow and expensive)
Wallboards (all seem to be acrylic/PVC - are there any other options?)
Tiles need to go on something solid. Either cement boards or marmox/kerdi/element XPS snadwich boards.

All the install videos I found showed either
Wallboard screwed to plasterboard, or
Tiles on element/marmox which in turn is screwed to noggins or glued to block wall

Now. I have 100mm PUR on the external walls. Can I just glue wallboards to those direct? Or do I need to glue something more rigid on first? (marmox/element) How thick? Instructions suggest 6mm on a solid wall for tiling over. 9,/10/12mm instead of plasterboard to span noggins.
I could go for extra solid and put up cementitious boards, but that seems like overkill (and a lot more work).
A PUR sheet glued to existing solid block+plaster wall is fairly rigid so I think just putting wallboards on direct should be fine, but I'm not sure which adhesive to use. Putting up 6mm marmox first will make it more rigid and give a good key to glue to. But I can't find any instance of someone recommending attaching wallboards over marmox (only tiles). So maybe it's not a good idea/pointless?

Also I note that Abacus provide neoprene tape and paint-on adhesive for sealing joints between boards and gaskets for around fittings. How does Tescon fare when used as a waterproof tape? (I have lots of this already and suspect it does much the same job here).
This shows the wallboards and tapes (and a load of other things for fitting out a bathroom): https://youtu.be/vNYNigge1C0?t=2063

There are a lot of Wallboard manufacturers from very cheap 250mm wide strips at <£10 each to wedi 2600x1200 panels at £600 each. Other manufacturers are Abacus (M1), Bushboard Nuance, Multipanel, Showerwall, Lustrolite.
How do I decide which of these are any good? From the prices it looks like Wedi must be 'premium' and 'EasyPanel' must be cheap and cheerful, the others in between.

Any experience of these - do the colours rub off eventually on the cheaper end?

You mention Bushboard Nuance in your list. We have them and I'm very pleased with them - have mentioned them several times on here.

I don't see why they can't be glued to insulation sheets as long as the surface is flat. Bear in mind that the Nuance is not loadbearing so any fixings will need to go through it and the insulation into the structure behind. You have to use their colour-matched adhesive; it's an MS-polymer. It is used for sealing penetrations too. We didn't have any problems installing; just cut carefully to size and glue them up - they stay put once up.

edit: there are no trims with this system.

Wall board is nice in hard water areas, you can just squeeze it down and there's no grout to start looking grimey

<blockquote><cite>Posted By: djh</cite>
You mention Bushboard Nuance in your list. We have them and I'm very pleased with them
</blockquote>

Thanks for the recommendation. It does look like a nice system. They do 4mm panels ('acrylic') and 10mm ('designer' and 11 mm ('high-pressure laminate'). Which did you use? I guess the two thicker ones are much stiffer, and they have T&G joints, rather than glued MS-polmyer butt joints.

<blockquote><cite>Posted By: djh</cite>
> there are no trims with this system.</blockquote>

OK. which no doubt looks nice, but shouldn't there be some allowance for expansion in a wall-run of this stuff?

I note that Abacus M1 sysytem puts a silicone bead in an aluminium corner trim to allow for expansion: https://www.youtube.com/watch?v=PbYucDWoizM

Mostly this research has made me realise that to do it properly I should seal to the floor too (behind the panels), which means I need to choose that too, and then do the UFH I was hoping to put off for a few years as it's going to be hard to get in there when it's all finished. And I need to move the sink and either buy a shorter bath or miss out some wall insulation. The simple job of finally covering up one wall (which has been foil for about 6 years now) is exploding before my eyes...

Presumably there are floor materials which could be done afterwards and sealed to the front of the panels? Those floors with the curved, welded-corner, moppable upstands look like a really good idea. Is there a DIY version of that?

Posted By: wookeyOK. which no doubt looks nice, but shouldn't there be some allowance for expansion in a wall-run of this stuff?

Dunno, but we haven't seen any problems so far after five years and counting. But read the instructions, obviously

We have the HPL panels, I believe. I didn't know there was more than one type - ours are HPL over XPS core. They use MS-polymer-glued T&G 'click' joints.

Mostly this research has made me realise that to do it properly I should seal to the floor too (behind the panels), which means I need to choose that too, and then do the UFH I was hoping to put off for a few years as it's going to be hard to get in there when it's all finished. And I need to move the sink and either buy a shorter bath or miss out some wall insulation. The simple job of finally covering up one wall (which has been foil for about 6 years now) is exploding before my eyes...

Presumably there are floor materials which could be done afterwards and sealed to the front of the panels? Those floors with the curved, welded-corner, moppable upstands look like a really good idea. Is there a DIY version of that?

We have three shower rooms. In the ensuite the panels are along two sides of the shower compartment and sit above/in front of the raised edge of the shower tray. (The rest of the room is lime-platsered straw bales.) In the bathroom they just come straight down to floor level, except within the shower where they sit on its ridged edge as before. In the downstairs wetroom they terminate maybe 50 mm above floor level and the 'hospital contract' vinyl floor wraps up the walls behind the panels. AFAICT it's totally waterproof. We got that professionally installed. Actually we paid somebody to install the vinyl in the other rooms too, but he was just a local floor layer; the wetroom was a commercial contract floor man (from I think Glasswells). Actually the first one they sent said he couldn't do the job, since we required the floor upstand just to be glued to the lime plastered walls, no screws, but the second one did a brilliant job. I was happy to pay him/them.