Belt and braces leak proofing a shower

Are you definitely committed to the large tiles. A showerwall panel type solution will be the most reliable. Three large panels and corner beading mean there is no chance of any leakage with the added bonus of no grout to go mouldy. Its also easier to fit and easier to remove when the time comes.

Saw a really good video about this on the skill builder channel...can't remember exactly which one it was though.

https://www.youtube.com/@SkillBuilder/search?query=shower%20install

I did ours a few years ago with 12" tiles, membrane, waterproof grout and silicon everywhere. The only thing that failed was the trap. That needed a hole cut in the ceiling below to change.

If I do it again, I'd go for Nick's suggestion above for all the reasons he mentioned, plus, it's probably easier to clean.

In my (limited diy but have owned a few houses) experience, leaking showers and baths are usually a result of the tray moving or flexing.

Last one I did was a solid resin tray which I mounted on a bed of cement which was in turn on a sheet of 18mm marine ply over original floor. It won’t ever move.

The shower I removed was a 90’s fibres monstrosity with threaded bar feet wound out to the max which in turn sat on a couple of 1x2 timbers. It never leaked but I assume that was more due to the fact that the thing was so close to the ceiling that it was suffficiently uncomfortable to use that no adults had ever done so!

So with that in mind, what’s the tray, how is it fixed and how confident are you that it’s never going to move ?

Only thing that sticks out to me is fast set adhesive.

Are you well practised with tiling? I’m not, and I found fast set adhesive slowed my down as my mix was forever going off and I had to make a new mix. I’d have had the job finished quicker using regular adhesive.

Thanks all.
Unfortunately the budget is not unlimited. We've looked at panels a lot, and for ones we're happy with it's 1k+ 🙁 that's not doable to us.

Mugsys - will check that out, ta.

@petrieboy: good points! I'm pretty confident about the base. It's an 800mm resin Mira tray on 18mm ply, supported on 3 joists with multiple noggins. Tray is bonded to the ply with ct1, as per manufacturer. Tbh that's the only bit I'm confident about! Waste and pipework have been extensively tested and are all good.
More I've read the more I think tanking and membrane is daft, and the liquid alone should be ok.

Are you well practised with tiling

No! And thrice no! Standard it is, thanks!

Had a leaky shower a few years back, was all tiled and was a nightmare to find the leak. Knew it was coming out in the near future (it's out now) but as it was the only shower and had no bath needed to fix it. Shower panels were a lot quicker/easier to put up and fixed the problem. Lot easier to clean as well

From my experience - we have a concealed thermostatic shower (just the controls on the surface) and the concealed thermostatic controller failed and it leaked into the room below. Next time I'd get surface-mounted. Ohh and we had another leak when my daughter sat on the waste and the whole bloody lot overflowed out of the en-suite and made it's was through the ceiling. 🤯

The Mapei kits are excellent. Done properly you have no worries. I’ve probably done around 10 showers with them and never had an issue.

+1 for the shower panels idea. We had our full share of bathroon leaks and used Mermaid Panels instead of tiles. They work really well and worked out slightly more cost effective than tiles (but not by a great deal). Think giant tiles rather than lots of individual ones! My top tip would be to go for a really bold and bright colour but that is very much personal choice!

Thanks @colp that's good enough for me.
@johndoh that bit is sorted - isy a ceiling fed digital mixer. Partly chosen to avoid having to do stuff in walls and reduce chances of leaks!
Luckily we don't have a daughter. My son, however, hates showers 😀

Appreciate the love for shower panels, but we just can't find anything we like other than the expensive Mermaid ones. They're well over a grand just for panels, whereas budget for this tiled looks to be half that.

They’re well over a grand just for panels, whereas budget for this tiled looks to be half that.

But you won't need all the other stuff, so there is a saving there. Its also much faster to fit, easier to keep clean. Depends what price you put on your time. If you really are struggling to find some you like I'd rather compromise on the look and find some I quite liked than fit tiles.

Definitely use something like aquaboard or other cement-topped board. Alternatively Kudos shower enclosure.

Membrane for outside of enclosure areas.

Get some easy to access isolators for the water.

Make the thermostatic gubbins easy to access from a panel or from the wall behind.

Mapei flex adhesive works well.

some great advice here. my only experience is make sure that the tray is sealed before any screen is installed

Er, the 1st mistake I can see was a that you say the tray is fitted already and the wall boarding hasn’t been done?  If so, that’s incorrect.  The wall boarding and tanking should be done before the tray is fitted,  otherwise the only thing sealing it is the silicone on the tiling layer.

It’s an 800mm resin Mira tray on 18mm ply,

Check the tray where it seals to the trap. There have been some problems with this size of Mira resin trays being uneven around this point, making it impossible to achieve a seal, or at least not without a gallon of CT1 sealant, which you don't want. If it's of variable thickness, get it sent back to Mira.

Also ditch the trap they send with it and spend a small amount getting a McAlpine trap, will increase your chances of being drip-free.

I've gone pretty belt and braces with my current installation. Expanded polystyrene waterproof board up the sides, waterproof tape for all the joins and holes, then a separate self-adhesive tape where the tray meets the wall. I've gone for wallboard, sat on a bit of trim with sealant underneath, but as long as you've properly sealed the wall, tiles should be fine.

A showerwall panel type solution will be the most reliable.

This.

All the tiling I've done/ had done has been problematic eventually. 12 bathrooms.

All the plastic panels has been fine. 4 bathrooms.

We had a lot if problems with our old shower, and I've fitted a couple in previous houses.

Few things above I defo agree with...

Trap - buy the best one you can. They are often the first point of failure.

Thickness of tray around trap - I sent one tray back due to this. Second was better, but still slightly out. I sanded it a bit on the underside to even it out.

Shower panels are always going to leak less than tiles.

In the end I got an all in one solution where the bottom of the panels sit inside the tray. It has a roof on the enclosure too, so a lot less condensation in the room.

Also,

How easy is it to get under the shower to the trap? I had a lowish one fitted ( against my builders advice).

The twice I've had to leak chase, rolling about on the floor cursing, and generally hating plumbing, I've thought about his massive eye roll when I said no let's do it my way.

I've cheaped out on a bath. The bath flexed and silicone failed. The solution was rolling around on the floor hating joinery while reinforcing the cheap bath with a wooden frame.

Mostly just venting about rolling about on bathroom floors hating DIY, plumbing, wood, spanners that won't fit, life choices, being cheap, previous owners had fitted taps that were too spendy.

The spendy taps had seized onto the spindles of the cartridge. A 5 min removal job became 3h+ trip to plumbers merchant who muttered and grumbled his way through a large box of cartridges that didn't quite fit.

Good luck op! I hope all the preparations pays off 👍

@tall_martin - I feel your pain. I hate plumbing 🤬 it always requires you to have an extra, double-jointed, tiny, but long fingered hand.

No tool or part ever seems to quite fit properly, and the (what they laughably call) standards all seem to vary by tiny amounts.

How are people finding the plastic panels for longevity? I had some in a bathroom for about 6 years and slowly the coloured/printed layer started to peel, eventually coming off in great big sheets.

taping is done after the trays in.

As above failure is always mostly down to the tray moving.

Use good quality sealer.

Also on big tiles make sure the adhesive is strong enough for your tile size! 

Grout I did mine with swiming pool spec grout.

tiles are better than panels , no need to tank hardie backer board , slow set adhesive, bal grout or  epoxy grout

decent finish silicone around tiles onto tray  say 12mm bead, chamfer bottom of fixing rail for shower screen  so silcone from tiles onto tray doesnt push the profile away from wall, before you fit fixing rail pump clear silicone onto bottom where rail meets tray , hope that makes sense 

Thanks all, loads of great advice, all taken on board!

Tray is fitted with the supplied trap. Noted, will ditch it and buy another.

Re: the board/tray which to fit first thing. Quite a few people recommended it being done tray first. Space is at a premium so I went this way. It's not reversible without a mammoth amount of work 🙁 maybe I misunderstood them. I'll have to sit down and have a big think. It's fixed into a bit of board that it's not coming off, and the board goes under a stud to the next room.
It would need two stud walls moving and half the bathroom redoing.

You could tank on top of the board as the tanking should be waterproof.

If you backer board and tile your gonna be 25mm or so over the lip on the tray depending on your tile 

If there's enough room on the tray i don't see that being an issue.

You'll just never get the tray out without destruction of the walls

Ok, if the tray position is non reversible, then I’d use hardiebacker 12mm as the wall board and put a good bead of silicone on the bottom edge of the board as you fit it, to form as much of a seal as you can get, then seal it again before tiling.  As mentioned above Hardie backer doesn’t need tanking, it’s already waterproof as long as the joints and holes cut into it are sealed.

I’d not use rapidset unless you’re very proficient.  I use Kerakoll H40 gel as it’s slow setting but high grab for large format tiles.  The only shower panels I’d consider instead of tiles are Mermaid panel.  There’s some real tut around, the best is expensive for a reason.

Make sure you prime the cement board  before starting, and make sure your adhesive bed is full by back buttering and combing.

I’d use epoxy grout as well.

I’m a bathroom fitter and tiler by trade, happy to pass on info if it helps.

I Have a shower over the bath.  I used a 3 piece seal kit around the bath which goes under the tiles and the wall are plasterboard painted with a waterproofing membrane.  largeish tiles.  all done by a pro and not a leak in several years

In addition to what I wrote last night.  When I said hardiebacker at 12mm, I’d also be happy substituting with a foam cored cement faced board such as Delta or Wedi (brand names, others exist)

check the fitting sizes on your shower enclosure.  Because you’re boarding on to the tray, you’ll be taking 50mm away from the space (tiles and board). This could get a bit tight on some enclosures as normally you’d only lose 25mm or so for the tiles.

Thanks again all. Went to buy the cement board last night and realization hit that I may be running it close for the door. So I've gone with STS backer board (with associated adhesive and screws)from Wickes.

To give a bit more back story, this enclosure was already tiled and boarded with the STS board, but it was leaking out the back, and in multiple other places, indicating both primary and secondary seals had failed. After a lot of leak chasing we decided it best to rip the lot out and start again.
I'm still planning on tanking with the Mapei stuff and lapping the top of the tray slightly. I know the board should be waterproof, but it should have been before!

Is it best to run silicon around the tray and then fit the board hard down to it, or leave a gap of say 2mm that's pumped full of the stuff?

I'll put some noggins in the wall adjacent to the tray to hold the silicon in.

@Blazin-saddles what is the best brand of sealant please. I need to redo a bath/shower. Any tips for removing old sealant? 

Probably too late, but how about considering a 760x760 shower tray instead? Probably cheaper than knocking down walls if you are going to worry about watertightness.

@submarined - sounds like you’ve already thought about most of that then.  I’d probably put a good bead on the bottoms of the board as I put it in to try and make sure the gap is as filled as possible, normally you’d leave a gap and fill, but you’d want to be 100% sure it’s 100% filled.  Tanking paint and joint tape is probably a good idea for reassurance in your situation.

@myti - Dow Corning 785, but not available in many colours.  If you want colours, I use Tilemaster Silicone 3000 or Kerakoll usually.  

To remove use a Stanley blade to cut out as much as possible, the use a very sharp scraper or Stanley blade to clean up the rest.  You can buy a removal tool also, but it’s doing the same job IMO, possibly easier to use though.  The key to reselling though is get it as clean and dry as you can. Silicone doesn’t stick to anything wet, and doesn’t like sticking to other silicones either.

Screwfix sell a silicone removal gel. It's not a game changer but with a craft knife and then gel , followed by a scratch pad you can get back to where it needs be .
Dow Corning is great , mapei runs a close second.
Bal for adhesive and grout.
I have seen trays set on sand , low expanding foam beds , wooden cross beams . All worked but removal or maintenance was always an issue.
Don't lick your fingers and use them to smooth out the silicone , allegedly it introduces mouth bacteria and makes it go mouldy quickly and some of the anti mould chemical can be nasty

Don’t lick your fingers and use them to smooth out the silicone

And don't lick your fingers, use them to smooth out the silicone, then lick your fingers again. Although you may end up with a brilliant white tongue.

Seriously, get a profiling kit. Can't believe how easy it is in comparison.