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

@JohnMo @Nickfromwales @JpManning @stevenlee thanks for all the advice. Just wondering if you have thoughts re above?

Currently thinking;

• Stone resin shower tray

• tilebackerboard floor and shower walls direct onto egger (with peel and stick removed)

• Taped and tanked joints

• Tiles on floor and shower walls.

Assuming that works then wondering about backboard before or after the tray… inclined to go after.

Thanks again appreciate all the insights.

2 hours ago, junglejim said:

@JohnMo @Nickfromwales @JpManning @stevenlee thanks for all the advice. Just wondering if you have thoughts re above?

Currently thinking;

• Stone resin shower tray

• tilebackerboard floor and shower walls direct onto egger (with peel and stick removed)

• Taped and tanked joints

• Tiles on floor and shower walls.

Assuming that works then wondering about backboard before or after the tray… inclined to go after.

Thanks again appreciate all the insights.

That plan sounds right to me. Lay and fix the floor backer board first, then bed the tray on top as the maker says, fully supported with no hollow spots.

On the walls I'd fit the backer board after the tray, as you're thinking, and bring it down so it sits just above the tray lip and overlaps the upstand rather than sitting behind it. Water running down the wall then ends up in the tray, not behind it. Leave a small gap there for a flexible sealant, and run tanking tape over the tray to wall junction, the internal corners and all the board joints before the tanking coat goes on.

Screw the floor board at the spacing the maker gives, onto a bed of flexible adhesive so it's fully supported, and tank at least the area around the shower. With posi joists there's always a little movement, so use flexible adhesive and grout throughout and a silicone joint at the floor to wall junction rather than grout.

5 hours ago, JpManning said:

On the walls I'd fit the backer board after the tray

Not the way I would ever do it.

I’ve never fitted wall panels after the tray has gone in, as how do you then stop movement between the fixed tray and the movement of the backer boards?

What is the shower tray sealed against?

No mention of an up-stand tray here afaik, so this cannot be introduced as part of the plan if it doesn’t exist.

Board the walls, then bond the tray down and against it. I’ve been at this for 3 decades and never a single leak or failure. Ever.

100% agree with @Nickfromwales here - boards on the walls first, tiles over the top (or whatever finish is going over the boards).

12 hours ago, Nickfromwales said:

Not the way I would ever do it.

I’ve never fitted wall panels after the tray has gone in, as how do you then stop movement between the fixed tray and the movement of the backer boards?

What is the shower tray sealed against?

No mention of an up-stand tray here afaik, so this cannot be introduced as part of the plan if it doesn’t exist.

Board the walls, then bond the tray down and against it. I’ve been at this for 3 decades and never a single leak or failure. Ever.

Fair point, and having thought it through you're right. With no upstand on the tray there's nothing for the board to lap over, so boarding the walls first and bonding the tray down tight against the board gives a solid, fixed face to seal to.

@junglejim I'd go with that order then: floor backer down, walls boarded, tray bedded fully and pushed back to the boards, then tanking tape lapped from the board down onto the tray edge before you tile, and a good flexible silicone at the tray to tile joint.

Thanks both for putting me right.

just a word to the wise, when bedding the board down leave a 5mm or a bit larger gap around the back and side edges, get a good slug of your favourite sealant (I use EBT) all the way down and along the gap then push the tray back to the backerboard, have loads of wipes and clean up the excess that is pressed out.

I'm not entirely sure about tanking tape from board to tray edge? Is this a thing, curious?

Edited 22 minutes ago22 min by crispy_wafer

23 minutes ago, crispy_wafer said:

just a word to the wise, when bedding the board down leave a 5mm or a bit larger gap around the back and side edges, get a good slug of your favourite sealant (I use EBT) all the way down and along the gap then push the tray back to the backerboard, have loads of wipes and clean up the excess that is pressed out.

I'm not entirely sure about tanking tape from board to tray edge? Is this a thing, curious?

Read this through. Saves me a boatload more typing, lol.

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