Shower tray installation

kjacko · 2 Jun 2020

Hi all,
So got a 1000 x 800 concrete/acrylic shower tray to be installed straight onto 22mm moisture resistant chipboard floorboards (not using marine ply). I’ve actually used FBall P131 as a barrier/sealer.
I put it on a 5:1 bed of mortar, but it failed me (came back following day and it just lifted off). Maybe it wasn’t wet enough. When I removed it all, it did crumble a bit.
So, I’m thinking, any reason why I can’t used plasterboard adhesive? (As I have a full bag, whilst I’ve ran out of mortar ingredients). It will mix thick, allow me to get the tray level, and certainly stick it down.
I know the puritans will likely say “ya gotta use marine ply base, PVA it and then a mortar bed”.
Well, I’m looking for viable alternatives please.
Go!

johnny2007 · 2 Jun 2020

I've always used tile adhesive (BAL is my first choice) and never had a failure.
Mind you, if you have a very unlevelled surface i won't recommend it.

kjacko · 2 Jun 2020

Thanks Johnny,
The floor is pretty even so that doesn’t concern me. Is the stuff you use flexible tile adhesive?
I’m still wanting to use drywall adhesive as I have a full bag just begging to be used.

johnny2007 · 2 Jun 2020

Don't use plasterboard adhesive.
This is what I use, a bit overkill someone said as it's also suitable for swimming pools, but I like to do things once:

https://www.bal-adhesives.com/products/single-part-flexible/

kjacko · 3 Jun 2020

Thanks again. But what’s so wrong with using plasterboard adhesive? It’s probably not flexible but then neither is mortar and that’s the recommended method.
I’m more curious about it than adamant if you know what I mean.

johnny2007 · 3 Jun 2020

I'm not sure plasterboard adhesive will last the test of time, in my experience of removing old plasterboard I found that it becomes chalky and crumbles easily.

JaimieH · 3 Jun 2020

Personally I always use flexible tile adhesive to bed trays. Can't really see any reason why plasterboard adhesive wouldn't work, after all the main purpose of bedding is to fill any voids and potential weak points underneath the tray. You'll definitely get a stronger bond than with sand and cement but don't forget to also bond the sides of the tray to the walls with a healthy amount of sanitary silicone. Once cured this will help stop any movement and provide you with another consistent seal to stop any possible leaks. The only thing I would recommend is to overboard the chipboard under the tray first with something like 6mm No More Ply or Hardibacker or thin construction board, basically something that won't be affected by water.

kjacko · 3 Jun 2020

Thanks fellas.
I bought some mapei flexible adhesive. The guy said they sell a lot of that for shower tray installs, so, ya know!?
I’m hoping that the newly laid 22mm moisture resistant chipboard floorboards, after having a coating of pva AND P131 will suffice.

johnny2007 · 4 Jun 2020

I wouldn't have used pva.
BAL APD is the correct product.

kjacko · 4 Jun 2020

Well, that was a flippin nightmare.
I screwed down some 6mm ply the same size as the tray. Painted some P131 on.
Went downstairs, put levelling compound on the kitchen floor.
Went back upstairs mixed the whole back of mapei adhesive, spread it using a notched trowel, laid the shower tray, but I couldn’t get it level. Trying to remove the tray to add more adhesive was super hard, good job I had suctions cups.
Relaid it and whilst it’s better it’s still not perfect, I put loads of adhesive on, so not sure why it was so damned hard.
Anyway. I’ll see if it’s set when I go back tomorrow.

johnny2007 · 4 Jun 2020

You have to level the external edges of the shower tray.
Inside, where you would stand, it's sloped towards the trap, so must remain unlevelled.
Apologies if you already know, but I attended a job once done by a "plumber" (also gas safe registered) who had levelled the inside of the tray.
We were forced to smash it up.

kjacko · 4 Jun 2020

Hi, yes i did know that the sides are what you level up to.

Having a few days off now so will test it when I get back.

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Shower tray installation

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