School boy error

[Dash J]

Bang on the money there white beam
Suction

 

[Rich Midge]

It was the guys at Instamac that informed me of the crystals, this is going back 14 or 15 years. Though I agree that suction is a major issue I can't see it being the be all and end all. A damp sponge across a skimmed wall would surely prevent the addy from skinning over or drying out too fast but wouldn't increase the overall bond. Somebody somewhere needs to experiment?!

 

[Dash J]

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.

I think suction is the be all
In a laymans term you are stopping the substrate from being so pourus by priming

Plaster,no primer,suck then pop de bonded

If it was a case of crystals then surely if you primed bonding plaster which is probably one of the most pourus substrates then you could tile it!
Me personally I would never tile bonding plaster if it had umpteen coats of primer

 

[Rich Midge]

Agreed bonding plaster will wick away moisture at a rate of knots but is only an undercoat plaster so doesn't have the inherent strength to support tiles regardless of priming or not. No addy manufacturer would guarantee their products straight onto bonding. Like I said earlier, I'm certainly no chemist just expressing an opinion. Personally I live by the prime everything rule.

 

[Dash J]

Agree mate prime everything

 

[White Room]

Agreed bonding plaster will wick away moisture at a rate of knots but is only an undercoat plaster so doesn't have the inherent strength to support tiles regardless of priming or not. No addy manufacturer would guarantee their products straight onto bonding. Like I said earlier, I'm certainly no chemist just expressing an opinion. Personally I live by the prime everything rule.

Ok, a plasterer puts a finish on dry bonding that suck moisture out so the top coat is worthless, you can prime till the cows come home and it would'nt make a blind bit of difference.

 

[Rich Midge]

Ok, a plasterer puts a finish on dry bonding that suck moisture out so the top coat is worthless, you can prime till the cows come home and it would'nt make a blind bit of difference.

Completely agree in that scenario priming would be pointless but I don't really get the argument sorry. No plasterer would apply a finish coat to dry bonding. They either do it same day or they prime. If however a plasterer was to do this, the finish coat would be so full of hairline cracks and hollow sounding that no tiler would consider it a suitable surface to tile on regardless of priming or not.

 

[Aston]

There's a positive spin on this because the plus side is, the tiles are going to be very easy to pop off so you can always start again and this time prime..Bet you'll never make that mistake again)

 

[widler]

Completely agree in that scenario priming would be pointless but I don't really get the argument sorry. No plasterer would apply a finish coat to dry bonding. They either do it same day or they prime. If however a plasterer was to do this, the finish coat would be so full of hairline cracks and hollow sounding that no tiler would consider it a suitable surface to tile on regardless of priming or not.

I have never primed a high suction backing plaster in my life, suction is a plasterers friend [emoji41]

 

[swanman]

grout will properly hold it

don't worry worst things happen at sea:hurray:

 

[swanman]

this is getting very technical
sounds like you are are chemists not tilers

 

[Diggy]

Don't panic Millington , they aint gonna drop off tomorrow. I spoke to BAL about this years ago and the tech bod then told me you might get a prob in 20 yrs time.

Just from now on prime your plaster walls and try not to lose any sleep.

Diggy