School boy error - TilersForums.com

[Millington Deco]

Hi, Guys I've just finished a kitchen splashback and used some rapid set adhesive on new gypsum plaster but forgot to prime first. Will this definitely fail and if so how long before this will happen?

 

[Qwerty]

No, as long as the plasterboard wasn't dusty you will be just fine (assuming the fixing method of the tiles was correct of course)

 

[Dougs Third Go]

Geoff, it's onto plaster not plasterboard, I reckon you'll see the tiles popping within 3 months. Not sure how you forgot to prime though..

 

[Rich Midge]

Oh dear! This will deffo fail, could be as quick as a day or two. You may be lucky and the grout will hold it all together but imo you want to hold your hands up and put it right. I'm presuming you're new to the trade, careers are built on reputation.

 

[Qwerty]

Aaaarghh!!!! RTFQ Geoff!!! Yep, will most likely fail as the others (who clearly read your post properly) have already said. Sorry, I have been carrying, cutting & fixing gypsum plasterboard for the past few weeks and I'm brainwashed by the stuff at the moment!

 

[kimboslash]

Ouch! They are coming off sooner or later.

That is the reason we have prep sheets on our van - so no matter how absent minded we are first thing in the morning we still go through the same process each time.

 

[cone]

Op, a wee bit of comfort or you here, I did the same in my own house over a painted wall and 12 years later, they are still on and I was curious about them last year and I tapped every tile, no hollow noise and couldn't pull off the one or2 I tried it on. In theory they should come off but who knows, your tiles might just still be on a decade from now.

 

[Millington Deco]

Looks like I've cocked up my first tiling job! I originally had tub ady planned for the job but switched to quick set at the last minute forgeting to take the primer into account. I will defo put it right tho as I want to take on more tiling work, looks like more homework for me then. :-(

 

[Stef]

Prime everything then this situation won't occur again..

 

[Millington Deco]

Thats great advice Stef, cone I've stuck and identical tile with the same ady on some gypsum under my sink to give me some idea of the time scale to failure if my phone doesn't ring before then.

 

[White Room]

I've seen tiles on a gypsum plaster no primer and they remained for many years, yes they should have been primed though...

 

[cone]

I've seen tiles on a gypsum plaster no primer and they remained for many years, yes they should have been primed though...

I prime and scrape all my work but what is the technical info on why primer is needed. How is it tiles stay on the wall when primed and come off easily when not primed.

 

[Rich Midge]

Crystals form between a wet cement based mortar and dry plaster. Bizarrely, this doesn't happen the other way hence why you can skim over render. By no means a chemist but this is the best I can do!

 

[Stef]

As Rich says, you will end up with ettringite crystals forming with a cement based adhesive against a plaster substrate.
Priming will give a chemical key but will also create a barrier between the two to stop ettringite forming.
I prime everything I tile, plaster, plasterboard the lot.
Read the guidance on your bags of addy & it will tell you whether to prime or not.

 

[White Room]

I prime because of the high suction from plaster, the cement based adhesive losses the moisture to quick to allow it to cure probably.
Was informed from a bod from Mapei that ettringite is formed when moisture/damp is present.