SMC Shower Tray

[waheed357]

Hi,

I need some advice laying my shower tray. Its a light weight low profile SMC shower tray. Some what flexible too. Subfloor is 18mm chipboard that im going to put 6mm tile backing board on for the tray. There isn't much in the instructions and just say silicon the floor.
The floor is not perfectly level, maybe out by 1 or 2mm in some places. Would using a lot of CT1 for example and using weights level and set the tray or should I use something like a tile adhesive instead to make sure its level? The back is not flat like a stone shower tray as can be seen in the photo. Thanks.

 

[denso13]

Flexible floor tile adhesive for me.

 

[Madrab]

I believe they recommend a flexible adhesive for setting down moulded trays. The sub floor does need to be level though so the tray sits flat on it and all the adhesive is doing is setting it down. The adhesive shouldn't be used to level out the tray, given the slightly flexible nature of the material that the tray's made from.

 

[dilalio]

If tray has ribs and not a flat underbelly then AFAIK it should take a silicone adhesive.

 

[Madrab]

I'm always one for using a silicone adhesive for tray's these days, especially for flat bottomed trays - having been asked to fit a few of these lightweight SMC moulded trays more recently though they do seem to follow a similar process as the formers do, where they are used more as a wet room or level with the floor approach.

They do all seem to ask for a totally flat base/SLC, or straight onto joists and with a flexi adhesive to set them into?

 

[denso13]

There are plenty which advise a full mortar bed below the tray and a powdered floor tile adhesive with a notched trowel is perfect for this.

https://www.plumbworld.co.uk/documents/lightweight-shower-tray-installation-guide.pdf "Note! Silicone sealants, foams, mastics, installation compound adhesive or similar MUST NOT be used as a substitute for cement."

https://manuals.plus/asin/B07Z4H337W

https://lakesshoweringspaces.com/wp-content/uploads/2014/07/Rectangle-SMC.pdf

https://images.thdstatic.com/catalog/pdfImages/f4/f4a02cb0-01c6-40f9-b72e-9f6016b5d9be.pdf

https://www.plumbworld.co.uk/documents/lightweight-shower-tray-installation-guide.pdf

Subfloor is 18mm chipboard that im going to put 6mm tile backing board on for the tray.

To be honest the backerboard will add nothing, if the floor is sound then that will be ideal. Follow the fitting instructions, if they aren't clear then check with the supplier.

 

[dilalio]

I'm currently laying a 1400x900 stone resin tray, flat bottom.

The base is part 18mm ply and part concrete hearth.

I've primed the ply and brought it up to level with the hearth, using a 4mm skim of mapei kerraquick.

I'm applying mapei waterproof kit to that and 150mm up the walls with the tape embedded.

Then it'll be a combed bed of kerraquick with a 10mm round notched trowel.

MI's ask for a solid bed but the tray can also be raised on legs... Has holes for them... So if it can sit on legs, why does it need a solid bed???

Odd that one!

 

[Madrab]

It all seems to depend on the manufacturer that is detailing the installation method as to what they ask for. That is 4 different methods that they ask for when it comes to MSC trays

Silicone sealants, foams, mastics, installation compound adhesive or similar MUST NOT be used as a substitute for cement."

and then in the plumbworld link they do say to use Installation compound adhesive, even using a contact adhesive -

seems there is absolutely no standard when it comes to setting trays down these days. Quite honestly, these days I will always go with what makes sense rather than what they ask for, hasn't failed me yet.

 

[Madrab]

MI's ask for a solid bed but the tray can also be raised on legs... Has holes for them... So if it can sit on legs, why does it need a solid bed???

Absolutely - there is no common approach and every one seems to contradict everyone else these days, doesn't make it easy.

As suggested I just go with what is known to work and that can actually be different tray/surface dependent

 

[denso13]

and then in the plumbworld link they do say to use Installation compound adhesive,

But still ask for full coverage, not sure how that'll happen. Each to their own I suppose.