Shower tray

[Ashworth1]

I have purchased a stone resin shower tray that needs to be layed onto an uneven suspended timber floor. Ideally I want to lay it direct to my floor boards. It suggests sand and cement on play wood but have have also read you can lay it on flexible tile adhesive direct to the floor boards. Has any one done this with success? Thanks

 

[ktuludays]

The tray needs to be laid as per the manufacturers instructions, any deviation from that would void the warranty.

Regarding the floor personally I would always overboard to ensure a good solid base but I don't want any recourse from my customers so always cover my arse.

 

[oldbutnotdead]

Resin trays must be completely and evenly supported- there is no flex in them so you'll get issues (like the thing cracking) if there's a soft spot or dip in your floor.
Either use one of those nasty fixing kits (with the inevitable 100mm upstand) or ply and mortar.

 

[Madrab]

This is a regular issue and I repair a lot of these that haven't been installed properly. To ensure your tray sits level long term you really need to lift the boards and ensure that there are joists at the edges and centre where the tray will sit so it is supported properly. If there aren't and it's just floor boards with nothing below them then you need to insert supports as the boards will flex over time and burst any seal that is applied to the tray, I can just about guarantee that. You do also need a nice thick single piece level platform for it to sit on to ensure it stays level. If you want it to sit at the floor level then cut out the boards and replace the section with a similarly thick piece of WBP ply or OSB3 and then tank the whole wet area

If you want the shower tray sat into the floor so it is level with the surrounding floor then the boards need cut out and supports attached along the lenght of the joists the joists and then 18mm WBP ply inserted into the lowered section so the ply sits level with the top of the joists. Then tank the whole area and slot the tray into the lowered section your have created.

 

[Ashworth1]

When you say add supports do you mean noggins inbetween the joists.
Also regarding the tanking, do you mean the walls or under where the shower tray sits?

The manufacture instructions say it needs a 5.1 mix of sand and cement. For me with this sitting on wood it seems odd as it could crack over time. Surely adhesive is a better, longer lasting method? Or not

 

[oldbutnotdead]

When you say add supports do you mean noggins inbetween the joists.

Depends how good you are at cutting floorboards- using a multitool is very slow but enables you to cut on the nail line. Hand or circular saw you'll be cutting along the edge of the joists so you'll need bearers as well as noggins to support yr plywood

Also regarding the tanking, do you mean the walls or under where the shower tray sits?

Both

The manufacture instructions say it needs a 5.1 mix of sand and cement. For me with this sitting on wood it seems odd as it could crack over time. Surely adhesive is a better, longer lasting method? Or not

The mortar won't crack if it is on a solid base. Single piece of plywood (If you've got the depth I'd go 25mm rather than 18) gives you that solid base- if it moves it'll move as a unit rather than 3 individual floorboards moving separately.

 

[Madrab]

circular saw you'll be cutting along the edge of the joists

Erm, have to disagree ... you can plunge the circular saw to the same depth as the floorboard along the centre line of the joist, then either do the same at the tongue and groove to cut through the tongue with a sharpish bolster.

When you say add supports do you mean noggins inbetween the joists.

yes, in effect you want to create a main square/rectangular/triangular support connected to the joists underneath all 4 edges of where the tray will sit, where you can. This gives as much support to the tray and subfloor as possible. Use nice and thick CLS.

Use as thick a piece of WMP plywood/OSB as you can, I mention 18mm but that's as a minimum, if you can the thicker the better.

I used to use sand and mortar mix but I avoid it these days, the only place I may use it is on a concrete sub floor, any other surface I now use more modern approaches - adhesives and/or sealants.

I tank from at least half way down the wall down and over the platform that the tray will sit on. Use a tray seal where you can too. In my experience you cannot go too far to make the area waterproof. I also try to ensure there is more than one type of seal where possible, to act as a fail safe.