Shower tray fitting on wood decking

[G and J]

I’m having a couple of hours off the build, so of course I’m on here researching.   No hope is there.  

 

We have 22mm decking (a caberboard equivalent) upstairs throughout.  I believe it’s really nice and flat but I will check that carefully.  I’ve read up all I could find on here, and as a result I think …..

 

I don’t need to fetch up the flooring to replace with marine ply, but I do need to prime it.  I think this is for adhesion rather than waterproofing.  

 

The tray instructions say lay on a bed of sand and cement, but if the decking is flat then ct1 appears an excellent bedding material.  I can’t believe the mortar mix won’t just turn to dust over time, with footfall and temperature cycling (J has skin removing shower flow temperatures!). 

 

We’ve put 15mm green plasterboard with oodles of screws on max 400mm centres, and we can tank that after fitting the shower tray.  If it’s better or easier or both to do beforehand please correct me. 

 

The wastes are lurking in holes in the floor, all connected up and ready, they sit quivering with anticipation on their own special noggin so they can’t drop too low.  When I actually fit them to the tray I’ll put a wipe of ct1 on the trap itself under the rubber washer, then on the washer, before carefully not cross threading the top bit as I screw it in.   I’ve practised that a couple of times using a 12mm plywood stand in shower tray with a 90mm hole in it.   I really must get out more. 

 

Then I scrubby scrub the shower tray’s bottom, (a clean bottom always helps) before carefully squirting ct1 on the bottom of the tray before dumping it in place.  I then pull it away from the walls a bit and squirt yet more ct1 into the gap before pushing it home.  

 

Next day I run water into the tray and watch underneath for drips or expanding wet patches on my ceilings.  Simples.  

 

So what can I improve on all that?

Edited 6 hours ago by G and J
Guess who pressed return too early!

[Oz07]

Has anyone ever bedded one in on foam?

[MikeGrahamT21]

I’ve heard people using flexible tile adhesive in place of sand and cement, seems a good strong option which will flex with heat cycles and loading

[G and J]

52 minutes ago, Oz07 said:

Has anyone ever bedded one in on foam?

That would scare me.  Partly as I hate foam. 

[G and J]

47 minutes ago, MikeGrahamT21 said:

I’ve heard people using flexible tile adhesive in place of sand and cement, seems a good strong option which will flex with heat cycles and loading

There’s a good few posts advocating that too, and I guess from my point of view both will give a good, strong bond with enough flexibility to endure.  I’ve got ct1 and I’ve used it many times so I’m at home with it, hence my preference.  But I’m open to other viewpoints. 

[Nickfromwales]

57 minutes ago, Oz07 said:

Has anyone ever bedded one in on foam?

Nobody sane!

[Nickfromwales]

10 minutes ago, G and J said:

There’s a good few posts advocating that too, and I guess from my point of view both will give a good, strong bond with enough flexibility to endure.  I’ve got ct1 and I’ve used it many times so I’m at home with it, hence my preference.  But I’m open to other viewpoints. 

Is it a stone-resin tray?

 

If so, use flexible tile adhesive, it takes much better to the tray, and as you say using said mixture to scrub and key the underside so get a great bond.

 

2 hours ago, G and J said:

The tray instructions say lay on a bed of sand and cement, but if the decking is flat then ct1 appears an excellent bedding material.  I can’t believe the mortar mix won’t just turn to dust over time, with footfall and temperature cycling (J has skin removing shower flow temperatures!). 

Same here. Every one I've taken up to replace has turned to crumbs.

 

2 hours ago, G and J said:

we can tank that after fitting the shower tray.  If it’s better or easier or both to do beforehand please correct me. 

Do as much tanking as you can before fitting, so you don't get it over the new tray. It's best to leave that cure and CT1 the tray to tanking, and then just cut in a final coat after you've fitted the tray. Lots of thin layers and make sure it has dried before fitting the tray.

[G and J]

8 minutes ago, Nickfromwales said:

Is it a stone-resin tray?

 

If so, use flexible tile adhesive, it takes much better to the tray, and as you say using said mixture to scrub and key the underside so get a great bond.

They are, so will do.  Maybe bulk buying 38 tubes of ct1 wasn’t such a good idea….

 

9 minutes ago, Nickfromwales said:

Do as much tanking as you can before fitting, so you don't get it over the new tray. It's best to leave that cure and CT1 the tray to tanking, and then just cut in a final coat after you've fitted the tray. Lots of thin layers and make sure it has dried before fitting the tray.

Gotcha.  Makes perfect sense.  

[Nickfromwales]

2 minutes ago, G and J said:

Maybe bulk buying 38 tubes of ct1 wasn’t such a good idea….

🤐

[G and J]

6 minutes ago, Nickfromwales said:

🤐

For sale, one carefully owner…..    lol

[crispy_wafer]

I think you’re pretty well covered with advice, but I’d second getting as much tanking done beforehand, for what it’s worth I also covered the floor, any joints that were under the tray too, and all round the keyhole for the waste.  Flexible tile adhesive was also used.  
 

oh, have an old towel, some wipes nearby, and someone nearby to help wipe down cos tile adhesive sticks like sh*t and gets everywhere you don’t want it too 😂.

[G and J]

53 minutes ago, crispy_wafer said:

tile adhesive sticks like sh*t and gets everywhere you don’t want it too 😂.

I knew there was a reason I wanted to use ct1 lol

[Nickfromwales]

5 minutes ago, G and J said:

I knew there was a reason I wanted to use ct1 lol

Bucket of water and a sponge, is all you need. Wash your hands and tools frequently, but if you've done the job properly you should not see any tile adhesive after fitting the tray, whatsoever. It should all be under the tray only, so if it's looking like it's going to ooze out everywhere, you mixed too much up!!

 

Remember you do not put tile adhesive under the lip that runs around the tray underside, the adhesive stays away from those so they can move / flex, you just silicone these gaps later on.