I’m guessing this is a bit of a rabbit hole but I’m looking at options for bathroom. Currently thinking of a former shower tray with waterproof boards on the walls and possibly floor then tiling over. I’m looking at jakoboard and kerdi and leaning towards kerdi but interested in anyone’s experience and thoughts? Thanks 

Green plasterboard? Waterproof tile adhesive and tiles. Low profile shower tray?

Both work well, it mostly comes down to what's behind them and how much faff you want. In a timber frame I'd lean towards a proper backer board in the shower area rather than relying on a membrane over standard plasterboard, because the frame will move a bit and a stiff board screwed at close centres gives tiles a better base.

The XPS boards (Jackoboard type) are quick to fit: screw with the washers into studs at about 300mm centres, then tape and seal every joint and screw head with the matching system tape. On an outside wall they also add a little insulation. Kerdi is an excellent waterproofing layer and can go over plasterboard or cement board, but it needs a flat, rigid surface and it's fiddlier than people expect, especially inside corners and pipe collars.

Whichever you choose, the bits that fail are the junctions: board to tray, wall to floor, and around the valve and waste. Use the proper corner pieces and collars rather than trusting silicone. If you're going for a former tray, stiffen the floor with extra noggins and a decent deck, as any deflection will crack the grout. Green plasterboard is fine outside the splash zone but I wouldn't use it in the wet area itself.

On 13/10/2026 at 19:51, junglejim said:

I’m guessing this is a bit of a rabbit hole but I’m looking at options for bathroom. Currently thinking of a former shower tray with waterproof boards on the walls and possibly floor then tiling over. I’m looking at jakoboard and kerdi and leaning towards kerdi but interested in anyone’s experience and thoughts? Thanks 

Always used plasterboard plus tanking, on my many, many clients wetroom / bathroom projects. Never had a single issue or failure. 
 

I’m not a fan of the XPS boards on the walls as it doesn’t take point pressure as well, for one, but also because it’s reliant on the mechanical fixes which pull into and crush the XPS. 

 

If it ain’t broke……carry on as is. 
 

Plus, you have to tank both anyways so 🤷‍♂️

Agree with JpManning on the junctions. In my leak work the bathroom callouts are almost never the board or membrane failing, it is water getting behind at the tray edge, the corners or through a cracked grout line and then sitting there soaking the frame. Whichever system you pick, tanking down to the tray and over the board to tray joint is the bit worth doing properly.

Thanks for the advice…. Plenty to think about.

I’m trying to work out the floor build up. I have posi joists with 22mm eggar protect flooring. For a tiled finish I’m wondering if I should tank the floor with anything, lay tile backer or something like ditra to decouple.

Feels like a bit of a minefield so another steep learning curve 👍

40 minutes ago, junglejim said:

Thanks for the advice…. Plenty to think about.

I’m trying to work out the floor build up. I have posi joists with 22mm eggar protect flooring. For a tiled finish I’m wondering if I should tank the floor with anything, lay tile backer or something like ditra to decouple.

Feels like a bit of a minefield so another steep learning curve 👍

Edit: the floor is egger advanced peel clean. See photo