Shower tray nonsense

[Aaron Cabrele]

hoping I’ll get sing replies to this one in tiling since I’m guessing a lot of tilers have had to fit trays.

A couple of days ago I laid a 1200x800 Stone resin shower tray, the flopping heavy type. It went on a completely level 25mm ply base screwed to joists. My instinct was to lay it on construction adhesive since no levelling was needed, or tile adhesive, but I was a good boy and did exactly as the MI said on a 5-1 mortar mix.

Since then I’ve put the no more ply boards on the edges but not yet finished the walls (which will be Beton Cire, a waxed concrete).

Coming today back to the tray I’ve noticed the mortar is very crumbly, the bits splodged on the edge etc you can crush in your hand.

I’m now worried over time and with the small movement of a timber floor it’s going to crumble away underneath and eventually fail.

I wish I had gone with my gut instinct and used flexi tile adhesive. To pull it out now will be a bit of a nightmare but possible. Am I worrying about nothing?

 

[gcol]

Did you seal the surface prior to laying the mortar?

 

[foxhole]

Why do you require replies to be sung?


You can always crumble splashes of mortar no matter how strong the mix, the main lump should be fine.

 

[Aaron Cabrele]

Hehe, I just like the sound of your singing voice. Thanks for the replies.

No actually I didn’t seal the ply. I re read the instructions and it doesn’t mention it, just 18mm ply minimum. I’ve just noticed in the “materials required” it mentions an anti crumbling additive, however it doesn’t mention it in the step by step so I didn’t do that.

My father in law came over (builder back in the day) and said the mix looked fine to him. My opinion of crumbly might be over critical.

If it does fail somehow in years to come the only real extra work is going be taking the shower enclosure back out which won’t be too difficult, so I’ll leave it and see how it goes.

I don’t understand the logic of needing a full mortar layer when these things can be supported by a handful of plastic legs as an option, with unsupported spans therefor able to take the weight of a person standing on it.

 

[gcol]

The mortar is to even out forces on the tray. The tray will not necessarily be pefectly flat so if you just sit it on ply it’ll likely crack.
Sound like the ply has wicked moisture out of the mortar mix and it’s gone dry. Guess the question is.... do you feel lucky?
Probably be alright. Go have a beer and try not to worry. Just remember to tiptoe into the shower.

 

[flameport]

I don’t understand the logic of needing a full mortar layer when these things can be supported by a handful of plastic legs as an option, with unsupported spans therefor able to take the weight of a person standing on it.

It's the difference between will not crack, and might crack.
Particularly when objects are dropped onto the tray, not from just standing on it.
Likely things to be dropped from a height include the shower head, bottles of shampoo, etc.

Plastic legs also mean a huge step to get into the shower, and as plastic flexes and bends, leaks around the edge of the tray are likely.

 

[Aaron Cabrele]

Does that mean all trays installed on legs (and approved by MI) come under the “might crack” category?!