Bedding an acrylic shower tray with a foam base

[subzero155]

Hi. I am looking to bed an acrylic shower tray with a foam base on floorboards with 5mm plywood on top. Per manual, I will need a mix of sand and cement so I would like to know if anyone has some recommendations for a ready mix? I am wondering if the Blue Circle Quality assured Mortar or the Laeto Build-it Easy Mix Mortar is a good choice (which is better?). One more thing, how much mortar would I need for a 1200x900 mm tray with a bed thickness of around 8mm? Many thanks.

 

[Madrab]

What is it going down onto?

 

[subzero155]

Floorboards, and would lay 5mm ply on top of the boards.

 

[Madrab]

If you are going to use a bedding then you may be better off using a flexible tile adhesive rather than a mortar mix - mortar mixes on wood tends to dry out unevenly and crack more easily. Flexible adhesives are more suited to that type of base.

Personally I never use them now and use modern polymer/silicone adhesives but that would also be determined by the base of the tray.

 

[Diver Fred]

Floorboards, and would lay 5mm ply on top of the boards.

you need to make sure the boards are flat. 5mm ply is not sufficiently strong enough. You need to use 18 or 22mm plywood.
as for the amount of mortar - about a 10 litre bucket full.

once in do nothing on it for at least 36 hours better if you can leave it over a weekend.

 

[subzero155]

you need to make sure the boards are flat. 5mm ply is not sufficiently strong enough. You need to use 18 or 22mm plywood.
as for the amount of mortar - about a 10 litre bucket full.

once in do nothing on it for at least 36 hours better if you can leave it over a weekend.

The entire bathroom will have 5mm ply. Should I use 18/22mm only for the tray? And what about Madrab's suggestion of flexible tile adhesive instead of a mortar mix? Would that be more suitable?

 

[subzero155]

If you are going to use a bedding then you may be better off using a flexible tile adhesive rather than a mortar mix - mortar mixes on wood tends to dry out unevenly and crack more easily. Flexible adhesives are more suited to that type of base.

Personally I never use them now and use modern polymer/silicone adhesives but that would also be determined by the base of the tray.

Thanks. Will that be ok on a 5mm treated ply over the floorboard?

 

[Diver Fred]

The important thing is that the support for the shower tray is stable. So 18/22mm ply under that. 5mm for the rest of the room should be OK dependant on what floor finish are you using?

 

[subzero155]

The important thing is that the support for the shower tray is stable. So 18/22mm ply under that. 5mm for the rest of the room should be OK dependant on what floor finish are you using?

It is click vinyl flooring

 

[Diver Fred]

(Should) be OK. Be enough to hide the joins in the floorboards.

 

[Madrab]

I guess you are trying to minimise or level out the tray with the rest of the floor space hence using a 5mm piece of ply?

If it's going onto a floating floor with joists then if you want longevity out of it and want some flexibility to try and level it with the finished floor, then I would mark and cut the shape of the tray out of the floor boards - add in extra support to the joists with dwangs to create support for the outside edges of the tray, having as many joists supporting the main body of the tray as possible, then replace the removed boards with a single piece of 18/22mm OSB3 or WBP ply. That'll allow some flexibility with finished heights to match the rest of the finished floor space.