Shower tray install - how much of a gap to allow for sealing?

Kencollins · 11-08-2023 01:30PM #1

Hi all,

I am re-doing an en-suite bathroom, currently stripped back to the timber frame.

Shower tray is 1205 mm.

Timber to timber is 2050 mm.

Gap is 45 mm - minus 25 mm for tile backer board

I will build out the timber frame to take up the 20 mm gap, then tank and tile down onto the shower tray.

How much should I leave for a sealing kit? Would 2 mm each side be enough for something like a classi seal?

It's not something I can undo when I discover the gap is too wide or too narrow, so I want to get it right!

Thanks!

10-10-20 · 11-08-2023 01:37PM

"Timber to timber is 2050 mm." you mean 1250?

I'd go with slightly larger than 2mm each side, just in case there is an alignment issue. Plus a 4 or 5mm gap either side would be still acceptable for a good seal; so 3mm to 4mm!

Kencollins · 11-08-2023 01:44PM

Sorry, 1250!

Would you use a classi seal, or fill it with a high quality silicon and tank down over it?

Thanks for the help!

10-10-20 · 11-08-2023 01:58PM

https://www.boards.ie/discussion/comment/120965102#Comment_120965102

Never the silicon and over-top tanking... that sounds like a road to later pain as you'll have flexing. Classi seal or better/equivalent for me.

Sleeper12 · 11-08-2023 06:31PM

Classi seal all the way. Silicone as sealant is decades out of date technology. Classi or similar is industry minimum standard now.

GreeBo · 11-08-2023 07:49PM

+1 on tank everything and then classi seal tray to tanking.

I'm not sure I am following the issue, are you putting the shower into an alcove that is 45mm wider than the tray? If so, I'm assuming the alcove will be tiled on 3 sides.

Before doing anything I would check how square the alcove is by measuring the diagonals. I had an ensuite that was 25mm out top to bottom, so measure from multiple places. If its not square and plumb then built out the walls to make it so first and then see what you are left with compared to the tray.

Also determine where the trap & pipes will go with respect to the joists before you pick a side to build out :)

GreeBo · 11-08-2023 07:55PM

Edit to add, once you are square and plumb you dont need to worry about too narrow, if the tray fits then the seal will fit as it kicks out over the upstand of the tray, the less it has to stretch to the tanked wall the better really.

mickdw · 11-08-2023 08:31PM

Are 2 sides of shower to be built out or is one side aligning with wall outside shower.

Kencollins · 11-08-2023 09:22PM

The entire bathroom is only 1250mm wide timber to timber. The shower tray is 1200x700, and is going in one end, so essentially an alcove. I have all the plasterboard stripped back as it had gotten damp and rotten.

The waste is going to be a problem, because no matter which way I orient the tray it is over a 9 by 2 joist. The person who build the house in the 90's hacked the joists down by 3 inches where pipes were crossing instead of going through the centre, so one more cut isn't going to make a difference really!

Once I fit the tile backer board the walls should be plum to be within 1 or 2 mm.

Currently I think the plan is 12.5mm tile board on one wall, 1205mm tray, then two 12.5mm tile boards along the other wall. This gives me a total of 1242.5mm in the 1250mm gap, so almost 4mm gap either side of the tray to play with. Hopefully this will fit the classi seal properly!

Thanks for all the input so far.

GreeBo · 11-08-2023 09:38PM

Are you going to shim out the backer board to make it plumb and square or just fix to the battens?

If it was built in the 90's I wouldnt expect it to contain any right angles anywhere!

10-10-20 · 11-08-2023 11:02PM

Sistering some (or one) of those joists might be an option if you're concerned about flexing due to the notching.

Shower tray install - how much of a gap to allow for sealing?

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