How to install wainscoting in bathroom?

[samh25]

Planning on wainscoting bathroom and wondering what the layers/process would be?

In dry areas, the trim would go straight onto the plasterboard. But if we're waterproofing plasterboard (e.g. behind freestanding bath), we will need an additional layer (assume you can't paint over waterproofing!).

Is it a matter of looking for something like 3mm water resistant MDF to go over the plasterboard and then do the wainscoting on top of that?

Any idea how it's normally done? Thanks for your help!

[EricL]

Hello @samh25 

Waterproofing membranes do not produce a smooth surface finish like paint, and it might not look good when painted over timber dowels or MDF. Should there be any failure in the waterproofing the wainscoting will get wet and damaged. I propose reconsidering your design feature and tiling the wall and using a different coloured tile to create that wainscoting look you're after.

Let me call on our experienced members @Dave-1 and @Nailbag for possible ideas.

If you need further assistance, please let us know.

Eric

[Nailbag]

Hi @samh25 

Have to admit I had to look up "wainscoting" which I have never heard of before. But from what you are describing it definitely doesn't sound like the materials are going to comply with any form of bathroom waterproofing, especially anything involving MDF. Personally I would consult with a certified waterproofer to see what your options are.

Nailbag

[Dave-1]

Good morning @samh25 

I would try and redesign the area so you can "miss" the problem raising itself. Much easier to do that and long term you wont have an issure arise.

As @Nailbag has suggested if you are set on it I would have a chat with a certified waterproofer for ways you could do it.

Dave

[MitchellMc]

Hi @samh25,

You need a protective layer over your waterproofing to comply with code and protect it from impacts. This is typically tiles. You could potentially clad it with cement sheeting, such as Villaboard. However, you'd need to speak with a waterproofer regarding fixing penetrations through the waterproofing.

So, you'd line that area with Villaboard over your membrane and paint it. Then you'd need to add your moulding on top of it to create the wainscotting. Typical timber or MDF is not going to be particularly suitable for a wet environment. If you are planning on using flat trims you could cut cement sheeting up and use that instead. For something fancier like colonial moulding, it would be difficult to find them in a water-resistant product.

I've created a rendering below to illustrate. Villaboard > membrane > villaboard > trim.

Please let me know if you have any questions.

Mitchell