Shower tray install fail

[JFDIY]

Yesterday I attempted to fit a large tray (1800x900).  I decided to use tile adhesive as whenever I've used mortar, all be it in a smaller tray, I found it was difficult to bed down.

 

Anyway the tile adhesive was better to work with, but I didn't put enough in the corner of the two walls, it was spongy and I left it overnight to see if it was just the adhesive being able to 'pant' before it hardened, anyway this morning it was no better, so I pulled it up.

 

Question is what to do different, it needs nearly 40mm of something and I'm now thinking of putting some spare egger floor board down and gluing/screwing that in first to bulk it up and not need as much adhesive, then I can hopefully use a proper notched trowel.

 

 

I'm guessing the likes of @Nickfromwales might have some words of wisdom, should I just make loads of dollops of adhesive or is there a better way?

 

 

Edited July 6, 2021 by JFDIY
Add pics

[nod]

Tile adhesive is fine 

You just need to make sure the whole area is covered In the same way as large format tile 

 

and use a flexible rapid set adhesive 

Edited July 6, 2021 by nod

[JFDIY]

Thanks @nod, I'm not overly familiar with laying large format tiles to be honest.

 

The underside of the tray is far from flat, around 30mm of slope, so wondering how you accommodate it in the bedding mix without using two bags of adhesive.

 

 

[nod]

You probably will have to use nearly two bags 

[Neill A]

You could "fill" the open underside of the tray first so that it has a known solid and level base first. Let that cure and then set it down on the hopefully flat and level floor with a thin bed of adhesive. At least then you know the underside of the tray (i.e. below where you stand) is properly and fully supported. 

[Nickfromwales]

Get a couple of 12.5mm cement boards, cut them to size and cut out a generous section for the trap. Then set those in on a bed of tile adhesive, make a load of piers rather than full solid bed, to match the pitch of the underside of the tray. Leave to cure. ( Rapid set makes this a race against time, so any novice should use standard aka extended set flexible adhesive and just accept the 24 hours between visits ).  
 

Set the tray onto as full a bed of flexible adhesive as is possible, and tap into place with a rubber mallet, lots of small taps, and level off.

When the tray has cured, 48 hrs from the get go, final fit the trap etc and test with a hose.

Make a 100mm deep dam of sand around the tray, flush to the topside of the tray, leaving just an inch or two gap at the outer edge / corner. Make a funnel out of stuff cardboard and get some builders leveller ( fibre impregnated self levelling compound ) and pour the entire void under the tray full to where it overflows the top of the sand dam. That will fill the entire void under the cement boards and also encapsulate the trap and pipework. 
Use expanding foam to seal around anything like final waste connection / gaps / cracks where the SLC could weep away, most importantly not into the waste pipe, so before pouring you must make sure all waste joints are rock solid!!  
Once done you can park a car on that. 

[Pocster]

2 hours ago, Nickfromwales said:

Once done you can park a car on that.

How do you get the car up the stairs ?