Drying time for mortar before priming surface for tiling

[OldKettle]

Hi,
I am currently repairing an area of tiles which had come loose, in a shower.

They are in the bottom of a recess, which is actually a window frame (still has a window on the outside, with boarding in between.

When I removed the tiles, the old adhesive was very crumbly, and when removed there was a gap of over 30mm down to the bricks of the windowsill.

Rather than trying to fill that gap with adhesive, I instead filled it with some mix in the tub mortar (about 25mm depth), which has been drying for 5 days now (at 20c and humidity of 50%).

I will be using Mapei Plaster Primer to prime before using Evo-Stik tile adhesive.

My reading of the instructions on the primer are that it should be used undiluted and that I should apply after 2 weeks of drying (on "cement:sand renders").

Just wondering how much I need to adhere to the 2 weeks, because this is the only shower in the house and so I would like to get the job done as soon as I can, but also want to make sure it is a decent job.

Any thoughts would be much appreciated.

 

[tell80]

No need for primer - return it unopened.
The mortar is ready to tile.
Clean out the gaps and then fill with silicone - wipe smooth.
Clean off all mortar smudges.
Set your sill tiles with a little slope to shed water and prevent it from pooling.
You can grout the edges where the tiles butt or you can silicone them?

 

[OldKettle]

Many thanks tell80.

I'm going to get the tiles back in today.

Can I just ask why the primer is not needed? Is it because of the type of substrate or because the tiles are not hanging vertically?

Thanks again.

 

[opps]

I do not understand the suggestion that you do not need to prime.

I am not a fan of premixed adhesives but the manufacturer does recommend sealing substrates. Bizarrely they recommend using their PVA.

https://diy.evo-stik.co.uk/sites/diy_evostik_uk/files/2019-11/TDS00376.pdf

Perhaps Tell80 can provide more info.

BTW, proper powder based adhesives do not become crumbly. They are cement based and not broken down by water ingress. The stuff in a tub becomes soft when it gets wet.

When tiling, I seal all plaster with (at a minimum) SBR. Unlike PVA, it doesn't emulsify when wet.

 

[tell80]

The area in question is a very small sill - no need for priming.

 

[Nige F]

f

Perhaps Tell80 can provide more info.

.

He'll always do that - and it's always right . In his mind.