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Discuss Bedding in a stone resin tray in the Bathrooms, Showers and Wetrooms area at UKPlumbersForums.co.uk.

  1. jonna

    jonna New Member

    Hi all, I'm looking for some advice installing a stone resin tray..

    Previously when I've installed these I've bedded them into tile addy on top of ply but they've always been the flat bottomed design.

    The tray I've installed on this occasion has a recessed/contoured bottom and it's on top of a timber platform topped with 18mm marine ply. I contacted the manufacturer (Simpsons) who stated that the tray would need to be bedded into a sand/cement screed. I asked if this needed to be a solid bed of a given depth, or spread using an adhesive trowel and I was informed that an 18mm trowel would be ideal. On Tuesday, I installed the tray using a wet mix (4:1), but I'm concerned that it's going to fail.

    Having installed the tray I put what was left of the cement on some scrap ply as I wanted to check how well it adhered and gained strength. The cement on the scrap ply when examined today is set but is not strong - there's no strength to it at all and it can be crushed back to sand with minimal effort.

    My concern is that the cement under the tray is in the same condition (weak and poorly adhered to the ply) so I'm considering relaying it.

    Question is, how should I do this given that I've followed the manufacturer's instructions already to this point?

    Thanks.
     
  2. ShaunCorbs

    ShaunCorbs Trusted Plumber GSR Top Contributor!!

    did you wet the bottom of the tray before you applied your mix and test board?
     
    • Informative Informative x 1
  3. jonna

    jonna New Member

    No I didn't wet the tray. The only thing I've considered doing differently was using a drier mix and use more of it. The mix I used had to be pretty wet in order to make it spreadable with the adhesive trowel. I assume by wetting the bottom of the tray, I'd help avoid the cement drying out too quickly - of the two materials though, (ply/stone resin) surely the ply would be more aggressive in leaching the water out of the screed?

    I'm half tempted to relay it using tile addy, but from what I've read manufacturers recommend sand/cement as it's stronger and less likely to crumble/fail over time. I could go back to Simpsons and query it with them I guess?
     
  4. Best

    Best Trusted Plumber Top Contributor!!

    It is more a bedding material and not an adhesive. Unlikely the tray will move. All that matters is that the adhesive sets to some extent. Personally I don't like sand & cement mix method that tray manufacturers recommend. Ordinary sand grit size can make a fairly course mix IMO.
    Remember that sand & cement will weaken if it gets drying too quick, because it needs a chemical reaction over a long as possible period. Putting a small amount on a piece of plywood will dry it quick, causing it to be weaker.
    Cement needs to be fairly fresh and don't use more than specified amount of mortariser, if any, and washing up liquid that people often use will also weaken the mix severely unless just a tiny drop
     
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    Last edited: Apr 27, 2017
  5. Best

    Best Trusted Plumber Top Contributor!!

    Sand & cement does tend to crumble on wooden floors.
     
  6. jonna

    jonna New Member

    Any suggestions on overcoming this? For reference, the base I've built is raised slightly to allow access to the waste and is topped with 18mm marine ply...
     
  7. jonna

    jonna New Member

    I take your point about it just being a bedding material as opposed to an adhesive. I guess I'm equally concerned about the strength of the screed. What do think to the suggestion of relaying, but using a solid bed with more mortar? I'd hope that by doing that, the base would retain moisture for longer and gain more strength..
     
  8. jonna

    jonna New Member

    It would raise the tray further, but how about I fix a cement backer board to the ply, then screed and sit the tray on top of this? Over the top? bad idea?
     
  9. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    I have a few questions?
    Is this a low profile tray or on a riser kit?
    If on a riser is it a frame that you made or is it a metal one that came with the tray?
    Did the manufacturer supply the boarding?
     
  10. jonna

    jonna New Member

    The tray is a Simpsons 45mm stone resin model which is advertised as low profile. The tray 'can' be mounted on a riser kit, but I decided instead to build a solid timber frame as per previous installations. The frame I've built consists of 2x4 timber with 18mm marine ply on top.
     
  11. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    I use a 4:1 or 5:1 mix when I spoke to the manufacturer of the very first one I did, they said that it does not need to set solid it needs to have a slight bit of movement in it. That is why some trays are set on flexible floor tile adhesive. I have done more than a fair few like this now and never had an issue. You should be fine. In my opinion.
     
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  12. Best

    Best Trusted Plumber Top Contributor!!

    Keep your tray as low as possible. I also think you should be okay with the way you have done it, so leave as is. Have confidence in your work.
    I have put a lot of trays in and many of them are fairly weak bed, but no problem with them. Think of it as a layer of trapped sand below the tray, - the tray has a soft bed, but the bed will not move away from beneath the tray.
    Any big gap around the edge bed, if it is crumbly, just scratch it out with a screwdriver or something and use some sand and cement mix with a bonding agent in it, if you want.
     
    • Agree Agree x 1
    • Informative Informative x 1
  13. Phil

    Phil Plumber

    Who on say a 1600 x 800 tray puts the waste by the wall or to the edge near the door.
    What are peoples preferences? I nearly had to turn mine round after it was fitted last week.
     
  14. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    I always put it where it will be easily accessible.
     
    • Agree Agree x 2
  15. jonna

    jonna New Member

    Thanks for the vote of confidence. I think I'd feel happier if the thin bed I laid the tray on was solid, based on what I've read the last day or so. Having applied it with an adhesive trowel (as advised by the manufacturer) I'm thinking the 'strips' of cement screed are more likely to crumble and move over time vs a solid bed. I'll see what it's like to stand on tonight, but right now I'm considering lifting it and laying on a 10mm solid bed...
     
  16. jonna

    jonna New Member

    Did you use a solid bed, or apply with an adhesive trowel?
     
  17. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    I always put a solid bed.
     
  18. Best

    Best Trusted Plumber Top Contributor!!

    I try to use a solid bed, but with some gap lines dragged through it to allow for the sand and cement to move to let tray bed level, - same as a bricklayer puts a gap in middle of mortar when bedding a brick.
    Using a solid bed is tricky though
     
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  19. jonna

    jonna New Member

    Thanks for sharing that. I'll see what the tray is like tonight, though not sure what to look for... I mean, it may take my weight now okay, but fail in the future. If the tray isn't fixed down I may lift it and re-lay on a 10mm solid bed.
     
  20. Best

    Best Trusted Plumber Top Contributor!!

    A lot of plumbers wrongly just set the tray straight down on the floor, without any bedding material. And if they are lucky enough that most of the the tray base, especially overall outer parts, touch the floor, then the tray won't budge.
    Once you bond the tray to the tiles/panels and to the shower doors, there won't be any movement am sure.
     
  21. cmel1975

    cmel1975 New Member

    Can't beat dry lining adhesive or bonding never had a problem with either
     
    • Agree Agree x 1
  22. Mikuni

    Mikuni New Member

    This is something that has puzzled me as well. I have installed many Simpsons trays both poly and stone resin. The manufacturers recommend the sand/cement base. We have often wondered how grippy or strong it is, but to date have not had any fail (phew!). I always use a 5:1 mix and a solid bed. It's a pain around the waste because you end up with virtually no mix there. I am surprised that the method works, so perhaps you can be leave it as it is. However, there could be something to be said for the solid base method? All the best. Mik.
     
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  23. Best

    Best Trusted Plumber Top Contributor!!

    Yes, bonding plaster is a brilliant mix for bedding in trays. Only worry is if water could get into it then it will soak up the water and stay wet for ages.
     
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  24. tt1987

    tt1987 New Member

    You should use epoxy glue to handle
     
  25. jonna

    jonna New Member

    A somewhat delayed reply, but when I checked the tray (a couple of days after bedding it in), it lifted straight up. Went down the solid bed route based on advice here. Thanks to all who offered advice...