Installation of a low profile shower tray on a concrete floor

[Gofer Blue]

I am replacing an existing tray because of my and my wife's advancing years. The one we have is on legs and consequently is quite high off the ground and my wife in particular is nervous of slipping and falling when exiting the shower. So we have gone for a large (1400 x 900mm) low profile tray to replace it. There are other consequential benefits as we will be using decorative PVC panels to cover the existing tiles (no more mouldy grout lines) and having a single sheet of glass (like a walk-in shower) so no doors with easier access and again no mouldy crevices associated with sliding doors!

We are in a bungalow with a concrete floor so by definition we have to excavate a channel in the concrete in which to site the trap and pipework to connect to the 110mm main drain. This has all been done (see photo). My dilemma (and almost paranoia the more I think about it) is what happens if any of the joints leak once the tray is stuck in place as there will be no way of telling if this occurs unlike with the elevated tray we had before.

A thought I had, because the tray will be stuck to the floor with adhesive and sealed all around the edges with silicone, is to simply drill a hole in the side of the 110mm pipe to allow any water to trickle down therein.There would not be a smell issue because the tray is effectively“hermetically” sealed over the drain.

I just wondered if anyone else has come across this issue or has any ideas of how to allay my fears!

 

[Madrab]

Just run that trap with copious amounts of water and check that everything is watertight. Once it's checked then as long as it doesn't get too much extra manipulation when being put into place once the tray's down, then it has to be trusted that it won't leak. The other point is that the tray can be 'stuck down' but it should only be 'stuck' so much to hold it in place - most of the adhesion should be at the wall touch points where it can then be cut and lifted again without major destruction.

 

[Gofer Blue]

Thanks Madrab. The wall panel supplier recommends panelling down onto the tray using the special trim provided so destruction would be the operative word if the tray was to be removed! This is because the trim has an upstand which sits behind the panel. I'm not really happy with this approach as I have always been a fan of tiling right down to the floor as you can see in the photo.
I have tested the pipework as per the photo and no leaks. I have also tested the trap in situ in the tray outside on a patio table as per a video I saw on YouTube and again no leak around the rubber gasket. It's just the thought that I wouldn't know if there was a leak once the tray is stuck down!

I'm thinking of using a cement based tile adhesive to mount the tray on. Would a dryish mortar mix be preferable?

 

[Madrab]

When it comes to the tray and the final wall covering - the standard is always fit the tray and then any tile/covering is fitted down to the tray edge. This ensures that any water running down the wall enters the tray and there isn't a direct path for the water to reach the floor, if the tray seal ever becomes compromised.

When I'm fitting a tray then the space receives a waterproof tanking covering - then the tray is bedded down in a silicone adhesive with a good quality silicone sealant at the tray edged and sides where it meets the wall - the tray is then slid/pushed into place - any gaps in the silicone along the wall is filled up with the excess smoothed out. Allow to set ideally for 24hrs - then the wall covering is fitted down to the tray and then another sealant layer is added.

This ensures there are in effect 3 seals - the one at the bottom edge of the tray to the floor - one main seal along the wall contact points and then the final one to seal the wall covering to the tray. It allows a level of redundant backup should the wall covering seal fail

 

[thomp1983]

When it comes to the tray and the final wall covering - the standard is always fit the tray and then any tile/covering is fitted down to the tray edge. This ensures that any water running down the wall enters the tray and there isn't a direct path for the water to reach the floor, if the tray seal ever becomes compromised.

When I'm fitting a tray then the space receives a waterproof tanking covering - then the tray is bedded down in a silicone adhesive with a good quality silicone sealant at the tray edged and sides where it meets the wall - the tray is then slid/pushed into place - any gaps in the silicone along the wall is filled up with the excess smoothed out. Allow to set ideally for 24hrs - then the wall covering is fitted down to the tray and then another sealant layer is added.

This ensures there are in effect 3 seals - the one at the bottom edge of the tray to the floor - one main seal along the wall contact points and then the final one to seal the wall covering to the tray. It allows a level of redundant backup should the wall covering seal fail

Sorry to jump in, Rob what do you use for the tanking covering? I've my own tray to lay soon onto ply so it's probably worthwhile me tanking the ply and up onto a couple of feet of the walls as insurance as its an upstairs bathroom.

 

[Madrab]

Depends @thomp1983 - if the walls are nice and new with say a cementitious or ply board like yours then the Mapei shower waterproofing Tanking kit is great value for money - comes with a sealer/primer, roll of edging tape and a large amount of polymer mapegum - The trick with this kit is primer everywhere> let dry> then a coat of polymer in all the corners> apply the tape while it's wet for good adhesion > then copious amounts of the gum over the tape to seal it in> let that touch dry > then coat wet area up to shoulder height with at least unbroken 2 coats as thick as possible or the amount in the tub allows.

If you are dealing with brick/stone/old plaster/dusty substrate walls then a cement based tanking medium like BAL Tank It or 1C is recommended - it is a much faster curing system and can bridge small gaps without tape etc but it is 3 time the price though very good.

Both are just as effective, area condition dependent.

 

[Gofer Blue]

When it comes to the tray and the final wall covering - the standard is always fit the tray and then any tile/covering is fitted down to the tray edge. This ensures that any water running down the wall enters the tray and there isn't a direct path for the water to reach the floor, if the tray seal ever becomes compromised.

When I'm fitting a tray then the space receives a waterproof tanking covering - then the tray is bedded down in a silicone adhesive with a good quality silicone sealant at the tray edged and sides where it meets the wall - the tray is then slid/pushed into place - any gaps in the silicone along the wall is filled up with the excess smoothed out. Allow to set ideally for 24hrs - then the wall covering is fitted down to the tray and then another sealant layer is added.

This ensures there are in effect 3 seals - the one at the bottom edge of the tray to the floor - one main seal along the wall contact points and then the final one to seal the wall covering to the tray. It allows a level of redundant backup should the wall covering seal fail

Thank you for the latest tips. Yes, I know that is the standard method for tiling/covering but I have never had a problem with the one I use - so far that is!! In this present case I have no option but to use the former anyway. Do I need to tank the bottom of the walls as they are already tiled? Maybe just silicone over the grout lines?

The tray I am using (Mira Flight low profile 40mm) would lend itself very well to a silicone sealant being applied all around the base (edges and inner bits) as it has numerous radial ridges underneath with connecting ridges rather like a spider's web. I have seen a YouTube video where a plumber did exactly that. I am just a bit nervous if the tray is slid into the final position, then most of the sealant might just rub off? Even though we are using suction pads to lift/manouver the tray into position, the location is tricky so the final move must inevitably involve a sliding action.
I must admit this sounds an easier method than faffing about with cement mortar or tile adhesive.

One last point. The trap manufacturer (McAlpine) states in the fitting instructions that a neutral cure silicone sealant can be used if desired on the rubber trap seals. This is tempting as a belt and braces approach but my gut feeling is that I would rather not, as the test run I carried out did not show up any leaks. Just concerned whether the silicone seal may fail in time?