Do I need to prime my plastic shower tray??

[rkidday]

These are the bedding instructions for the GRP shower tray I am installing (it looks like the GRP is moulded around a plastic base)

'Install the shower tray on a 15mm depth of weak cement

mix (sand/cement ratio 5:1). Tile adhesive can be used as
an alternate to sand or cement.
Please note if using water based adhesives, to enhance the
bonding it is suggested that a suitable primer is applied to
the base of the shower tray before installation.'

I plan to fit the tray using tile adhesive on top of boarding primed with an acrylic primer.

My questions:

• Can anyone recommend a good tile adhesive for this job (preferably non water based so that primer is not required)? - I've got a tube of Wickes waterproof wall adhesive handy but I assume this is water based.
• What type of primer should be applied to the base of the shower tray if using a water based tile adhesive?
• Can I get away with less than 15mm using tile adhesive as the tray is wider than the recess and therefore I've chased into the block work (so have limited adjustment). Also to get the required drop the tray is already quite high and I'd like to minimise this (I can't change the plinth height now) - see pictures.

DSC_0521_

• rkidday
• 17 Nov 2015

DSC_0522

• rkidday
• 17 Nov 2015

 

[flameport]

Water based means anything that is ready mixed, such things set by drying out. With a plastic tray on top and acrylic primer underneath, that will take weeks/months/for ever.
Use the sand and cement, which sets by chemical reaction. Or tile adhesive which is supplied as powder in a bag.

Thickness isn't important - making sure there are no air gaps and the tray is completely supported is.

If that 'boarding' is chipboard it needs to be replaced with plywood. Chipboard will disintegrate in the presence of moisture.

 

[rkidday]

Thanks for your quick response. Yes it is chip board which has now been glued and screwed to the plinth. However I did 'seal' both sides and the edges with the acrylic primer. I'm tanking the shower walls with Aquaseal so how about I put that on the chip board base before putting the tray down?

Cheers.

 

[Nige F]

If you use a band of classi seal on the tray and stuck to the walls you should be fine - don't know about aquaseal though

 

[Jackrae]

Looks like you're sliding the tray into position. If that is the case then you will have severe problems with the bedding compound being pushed forward by the tray resulting in ineffective support. Ideally the tray should be laid onto the bedding compound and lightly and evenly pressed down onto it.

 

[rkidday]

Looks like you're sliding the tray into position. If that is the case then you will have severe problems with the bedding compound being pushed forward by the tray resulting in ineffective support. Ideally the tray should be laid onto the bedding compound and lightly and evenly pressed down onto it.

I've got ~10mm clearance to slide the tray in. If it proves too difficult to hold the tray above the tile adhesive while sliding it in I'll use thin strips of timber as rails to keep it above and remove these once it's all the way in. The tray is very light so i think I should be able to manage this. Thanks

 

[Madrab]

Do you not have enough clearance to be able to angle the tray in? Slot the left hand side in and then drop it down and then slide to the right?

You do need to seal up the chipboard for sure. The aquaseal should do the trick admirably, just give enough time to set fully before any further work on it.

Remember to run a good quality silicone around all 3 walled sides of the tray before it goes in too so you are providing the 1st water seal around the tray.