The time has come to fit the wet room tray.

[MikeSharp01]

Well after a few months of work from laying the concrete around the mould / pattern or whatever the time has come to fit the actual wet room shower tray base and I am looking for ideas on how best to do this and what compound to use. The pic shows the underside of the tray with a lattice of ribs. The recess in the slab is flat bottomed and concrete. The tray fits into the recess in the slab perfectly but I now have to bed it down and I can see some possible issues. I have 5-8mm of height I need to make up so whatever I bed it down on has got to make that up or I will have very thick grout under the tiles. What would be a good compound to bed it down on. A sharp sand / cement mix or some such?

 

My second concern is / are the air pockets that will form in the lattice structure and may make getting it to bed down a problem and indeed might cause it to move if the air expands while the bedding material is drying. I could fill the pockets with the bedding compound, whatever it is to be, before I lower it into position to cure that problem but whatever happens I don't want it moving off level while the compound dries.

 

Any thoughts welcome.

 

[Nickfromwales]

What make tray is it mike? The MI's should state the methods of fixing for both solid and floating floors. 

 

Ill add add to this in a bit

[Dudda]

It's an AKW SureForm shower tray. I could pretend I knew from looking at it but I zoomed into the sticker on the image

 

Instructions are here:

https://www.akw-ltd.co.uk/wp-content/uploads/2016/06/14-021-019-SureForm-Installation-Instructions.pdf

 

I'd go for the sand and cement mix to bring it up a bit and put some in behind the honeycomb structure as you said.

[PeterW]

+1 to the sand and cement - make it a 5/1 mix with some FEB or similar and don't be afraid of making it a bit wetter than normal as it will settle well into the voids with a gentle tap of a rubber mallet ....!

[Nickfromwales]

I'd use cementitious powder, flexible tile adhesive, not sand and cement. Unless you use a very good priming agent the sand / cement will be hard to get to stick and stay down. Also, the S/C mix will not adhere to the GRP at all, so I reckon you'll get a bit of a 'hollow' fix where the tray can bounce if it's not absolutely flawless in manufacture. 

Work the tile adhesive into the screed so as to get a good bond and make it slightly wetter than would be preferable so the excess fills the void around the trap when you compress down. Also, you'll need to put a big blob where the trap is going as the MI's for all these types of trays require the trap to he mechanically supported. 

[jamiehamy]

Mike,  can you share a pic of the base where the trap is to go please? I'm about to start the exact same and trying to work out the best way to accommodate the trap - I've left a big void in the concrete that will need filled. Keen to see how you are doing it. Is the trap going to be enclosed in cement?  Thanks!  Jamie

[MikeSharp01]

10 hours ago, jamiehamy said:

Mike,  can you share a pic of the base where the trap is to go please? I'm about to start the exact same and trying to work out the best way to accommodate the trap - I've left a big void in the concrete that will need filled. Keen to see how you are doing it. Is the trap going to be enclosed in cement?  Thanks!  Jamie

Yep Jamie here is the tray recess and associated tile recess just after I skimmed it over to smooth out the lumps and bumps. It was made using a former, second picture. (The concrete was poured through the holes that were then capped.

 

Many thanks all, think I will go with @Nickfromwales suggestion as the non adherence of sand & cement seems to make good sense.

[jamiehamy]

Thank you,  that's really useful. So if you need access to the trap in future.  You lift the tray? I wasn't sure if it was realistic to make it accessible in that floor makeup. 

 

Thanks again.  J

[Nickfromwales]

41 minutes ago, jamiehamy said:

Thank you,  that's really useful. So if you need access to the trap in future.  You lift the tray? I wasn't sure if it was realistic to make it accessible in that floor makeup. 

 

Thanks again.  J

Nope. The tray goes down and stays down . The trap is called a 'self-cleaning' trap ( which means you can clean it yourself ). 

This is an Impey linear 2 for eg.....

 

The last shot is the vertical outlet staring down into a 110mm soil bend ( as Impey provision for their trap bodies at 110mm, tres bien ? ). 

 

Bingo. 

[MikeSharp01]

1 minute ago, Nickfromwales said:

Nope. The tray goes down and stays down . The trap is called a 'self-cleaning' trap ( which means you can clean it yourself ). 

This is an Impey linear 2 for eg.....

Actually the trap can be removed as the centre of the trap lifts out and you can then get at the outlet and the remains of the trap, you can then remove the connection at the stack end and withdraw it through the groove created in the slab between the trap and the stack. Once it is all in and pressure tested I will probably fill it with foam to remove possibility of vermin living in there.

 

I was worried about casting the mould into the slab as it is does provide some interesting stress points in the slab that might lead to cracks propagating from the corners. In this slab its not a particular problem but in the house slab it is vital, in my view, that the mould has a continuous ring of rebar around the mould to prevent any such propagation. I hope the slab designer will build this in if not I will work with them to get it included.

[Nickfromwales]

1 hour ago, MikeSharp01 said:

Actually the trap can be removed as the centre of the trap lifts out and you can then get at the outlet and the remains of the trap,

What I said above ? The tray stays down, 

For clarity, the trap body is the part that is bonded to the underside of the tray, so cannot be removed from above as it's physically bigger than the waste hole in the tray . The trap 'bucket' is the removable part ( see images above ) which gives access to the trap body and outlet for deep cleaning . 

1 hour ago, MikeSharp01 said:

you can then remove the connection at the stack end and withdraw it through the groove created in the slab between the trap and the stack. Once it is all in and pressure tested I will probably fill it with foam to remove possibility of vermin living in there.

If you see the MIs they state that the trap must be mechanically supported / fixed, so as to be load bearing should anyone put their entire body weight on one foot whilst standing directly onto the trap. If you fit the tray according to the MIs then your latter proposal won't work. Also, backfilling with foam is actually stated in the MIs as a big no-no .

Vermin love to nibble through foam and make snug little homes in it . Keeps them nice and warm 

[MikeSharp01]

7 hours ago, Nickfromwales said:

If you see the MIs they state that the trap must be mechanically supported / fixed, so as to be load bearing should anyone put their entire body weight on one foot whilst standing directly onto the trap.

Yes thanks @Nickfromwales, the tray stays down it will be covered in tiles so once down that will be it. What I have done is fix some old plastic fairing in layers 6mm & 3mm thick under the trap on the concrete of the slab to support the trap so you cannot push it down but the way the trap connection works it can be slid out underneath along the channel as the two are connected together by a threaded section that drops through and screws into the lower portion of the trap. This is one reason why the grout fixing the tray down need to be right as it must end up with the trap sitting on the plastic spacers. The other approach I considered was to put the tray in attach the trap, test it, and then run an amount of slurry in the bottom of the void up to about 10mm above the base of the trap, which once cured will support it, this means I can be less worried about the fixing compound for the tray itself. I hope that once I am confident it is leak proof I won't ever need to move it hence the foam idea. Agree on the foam, I guess the little critters love it and I will find another solution to that one, I could back fill it with more slurry or create a very close fitting shroud around the stack and seal it with silicone.

 

Fun this.

[jamiehamy]

On 7/4/2017 at 09:42, Nickfromwales said:

I'd use cementitious powder, flexible tile adhesive, not sand and cement. Unless you use a very good priming agent the sand / cement will be hard to get to stick and stay down. Also, the S/C mix will not adhere to the GRP at all, so I reckon you'll get a bit of a 'hollow' fix where the tray can bounce if it's not absolutely flawless in manufacture. 

Work the tile adhesive into the screed so as to get a good bond and make it slightly wetter than would be preferable so the excess fills the void around the trap when you compress down. Also, you'll need to put a big blob where the trap is going as the MI's for all these types of trays require the trap to he mechanically supported. 

I'm nearing the time I need to do this - it's stone resin tray - still recommend flexible tile adhesive @Nickfromwales rather than 5/1 S/C? I'll prime the concrete floor before doing either. 

[Nickfromwales]

Mix a bucket of S&C and another with flexible tile adhesive. 

Push your left and right hands, one into each bucket, and pull them back out. Then decide . 

[ProDave]

On 04 July 2017 at 21:54, Nickfromwales said:

Nope. The tray goes down and stays down . The trap is called a 'self-cleaning' trap ( which means you can clean it yourself ). 

This is an Impey linear 2 for eg.....

 

 

The last shot is the vertical outlet staring down into a 110mm soil bend ( as Impey provision for their trap bodies at 110mm, tres bien ? ). 

 

Bingo. 

Please don't tell me that all wet room shower trays must connect directly into 110mm

 

Not only have I already plumbed for 50mm pipe to each shower (with solvent welded bosses) but I could not fit 110mm with enough fall as they have to pass through the web of a posi joist.

[Nickfromwales]

Not at all. I only did that one as Impey allow it by making the outside of the trap body 110mm. If you see the pic looking down it reduces to 40mm . I could have cut the bottom of the trap body so it was fully open, but the discharge rate of that  linear drain is already crazy fast. 

[Nickfromwales]