Problem with Bal APD skimming/peeling on skimmed plaster

[hitthenorth]

Hello - first post here but first thanks for all the great info I've gained as a lurking guest

Having successfully tiled our ensuite a few years back I'm now tackling the bathroom.

I've put two coats of neat Bal APD on the plaster skim as per the instructions. I thought it had gone OK but when putting some pipework through for the shower I accidentally removed some of the plaster skim and in doing so found the primer had formed a latex like coating on the surface that can be peeled back like removing pva from your fingers or peeling skin after sunburn.

It sounds a lot like the issue here (had to change the url because I can't post links as a newbie :-( ) h t t p : //www.tilersforums.com/guest-area/54799-peeling-primer-skim-bal-apd.html

I thought it was confined to just that wall but sticking a bit of sticky tape on the other walls pulls a latex like layer off those too so I suspect it wouldn't hold the tiles.

So my questions are:

1. I rubbed the walls with a wire brush as they are fairly smooth but maybe I should have sanded or something as well - is that likely the reason?
2. What should the primed walls look/feel like if it has taken properly?

Seems knocking the plaster off was probably fortunate before I'd put the tiles on!

Thanks in advance.

 

[DHTiling]

I personally dilute primer to aid in the none skinning ... over application can also result in the skinning ..

 

[peteablard]

Never use Bal myself, is that what it tells you to do? Always thought it needed to be diluted for that exact reason!

 

[hitthenorth]

Yes the instructions say:

USE UNDILUTED ON:

• plaster walls/plasterboard when using a BAL cementitious powder adhesive
• tongue & groove floorboards
• anhydrite screed floors

USE DILUTED 1:1 with clean water on:

• dusty/porous plaster walls when using a BAL ready-mixed adhesive
• cement: sand screed/concrete floors

 

[AliGage]

Was the plaster polished? If so you'll need to dilute 1:1 with water.

 

[White Room]

As above it needs diluting as plaster can very absorbant.

 

[hitthenorth]

Guess I need to find a way of getting it all off and then sanding with a coarse paper?
Start with a diluted solution to start with after that?

 

[trevortine]

Does it look anything like this? Bal apd was applied to this wall and when dried just peeled off, ended up sanding the lot and reapplying, once sanded the primer took no problem. Use neat for plaster when using cement based adhesive.

 

[hitthenorth]

Yes it's not coming off quite as cleanly as that but the bits that are are coming off are like latex film like that.

Just noticed this comment at the end of a very long and slightly heated thread from here - h t t p : //www.diynot.com/forums/tiling/bal-apd-peeling-from-new-plaster.306412/page-2

Anyway, I spoke with bal tech help again and was told that ape will skin to a certain extent. With this information I put a tile up, left it a week and tried to remove it. To say it was stuck fast is an understatement. As Richard predicted, wrestling it off the wall even removed a small patch of skim - this was actually very good news.

So, a big lesson learnt - As Richard said, I should have considered the system as a whole.

Confused by that as I don't think a film that pulls away with a bit of tape is a suitable surface to tile on unless the adhesive can still penetrate it.

Will speak to Bal when I can.

 

[Andy Tiler]

Hello - first post here but first thanks for all the great info I've gained as a lurking guest

Having successfully tiled our ensuite a few years back I'm now tackling the bathroom.

I've put two coats of neat Bal APD on the plaster skim as per the instructions. I thought it had gone OK but when putting some pipework through for the shower I accidentally removed some of the plaster skim and in doing so found the primer had formed a latex like coating on the surface that can be peeled back like removing pva from your fingers or peeling skin after sunburn.

It sounds a lot like the issue here (had to change the url because I can't post links as a newbie :-( ) h t t p : //www.tilersforums.com/guest-area/54799-peeling-primer-skim-bal-apd.html

I thought it was confined to just that wall but sticking a bit of sticky tape on the other walls pulls a latex like layer off those too so I suspect it wouldn't hold the tiles.

So my questions are:

1. I rubbed the walls with a wire brush as they are fairly smooth but maybe I should have sanded or something as well - is that likely the reason?
2. What should the primed walls look/feel like if it has taken properly?

Seems knocking the plaster off was probably fortunate before I'd put the tiles on!

Thanks in advance.

IMO generally the first coat mixed 3/4-1
And the second coat neat! But each manufacture varies I only use Tilemaster now! For everything very good stuff IMHO. I would phone Bal ask them to come out and have a look and ask them y they recommend putting the first coat on neat!!!!

 

[High Peak Tiling]

I personally use Weber Primers, I always dilute 1:1 on any surface you are describing, because as Allister said It may be polished and your primer wont adhere.

I recommend a soft sand paper rub over the whole plastered area (this shall key and polished/very smooth plaster)
Dilute the primer 1 part APD 1 part water. (the dilution also gives your primer chance to do its job before the finish cote dries the moisture out of it)

Good luck

 

[hitthenorth]

Thanks for the comments. Sorry for any delays in replying - think my posts are still moderated as a newbie.

Finally managed to get it off the smallest wall which was the worst one - going to try a few small areas with different concentrations and coats before I do too much of the wall.

 

[hitthenorth]

Quick update. Spoke to Bal technical support and they put me on to a local advisor, both very helpful. Suggestions were as I suspected they would be that either the skim wasn't dry (although it's well over 4 weeks so unlikely) or the surface is too polished (most likely). Suggested sanding back and applying a coat of 1:1 and then a coat of neat, and if that didn't work maybe moving to a different product such as SBR.

I roughed up an areas as best I could and did two very thin coats as suggested above with the best part of 24 hours between each.

Certainly a major improvement - it's no longer peeling away even if tape applied and removed to test it (just flecks on the tape). The area where the tape is removed does allow more moisture through afterwards (plaster darkens a bit) but think it should be stable enough and that I'm over analysing things now - just lost a lot of confidence in how well it should work and what the result should be like.

 

[Mr T]

well looks like you have had the problems early on mate... plain sailing from here lol

 

[hitthenorth]

Hopefully - just glad me accidentally damaging some of the plaster revealed how badly the APD had gone on or things could have been a lot worse. Still not confident with the way it has gone on though - I'm sure the last time I primed things were easier than this!