strange bubbles in plaster - help

[berkshireguy]

Hello - I had an entrance porch and back extension added to my house. I got it painted and plastered in December but after a couple of weeks strange bubbles appeared on the walls but only in patches - almost look like the wall got infected. I first thought it might be because the plaster was not mixed properly so it is air bubbles but it only appeared afterwards and it is getting worse. Any idea what it might be?
Thanks for the help

 

[roughcaster]

Finishing plaster, if not troweled up properly, can/will leave small areas of blisters. Also,,if using bonding coat plaster as undercoat,, let the b/coat set properly before putting on the finishing, or this will cause blisters too. If you say the blisters are getting worse/ongoing, then there could be another reason. A picture would be most helpful.

Roughcaster.

 

[berkshireguy]

Thanks Roughcaster. Is the attached picture clear enough. Thanks

 

[berkshireguy]

this pic?

blusters on wall

• berkshireguy
• 18 May 2009
• 1

 

[roughcaster]

They are the blisters i expected to see. What makes them more prominent is the sheen on the paint, and/or light shining across them.

Roughcaster.

 

[roughcaster]

When the plasterer skimmed your wall, he would/should have noticed the blisters, and as the plaster went into the final set, they should have been troweled out. They would normally be gone with the final pass of the trowel. Although they are not what you would expect to see in a newly plastered surface, they wont get any worse than they are now.

Roughcaster.

 

[berkshireguy]

Thanks you but I feel my plastered need to corrrect it....

 

[roughcaster]

Thanks you but I feel my plastered need to corrrect it....

Certainly get him back, show him and tell him you're not happy.

Roughcaster.

 

[trowelmonkey1]

qucik sanding will sort it but he SHOULD have noticed that many, sometimes i get patches like that, never sure if it's a background plaster issue or a mix issue, either way like roughcaster says, on the final set they can be scraped off by hard trowelling

 

[dave1953]

Likewise I have seen these especially with Hardwall undercoat, however as has been posted many times, 2 COATS, not just a quick finish.

 

[roughcaster]

never sure if it's a background plaster issue or a mix issue

I think it's really a bad finishing issue. Any blisters "will" trowel out as the finishing sets, but if a plasterer thinks,,, "ahh,,that'll do",,,, and calls it a day,, when an extra 10 minutes or so,, would make all the difference, and any blisters remaining would be flattened out with the final trowel. I also know that sanding down a new plastered surface should really not be required, plus, it does more harm than good, and should be avoided if possible, but i'm not sure how it would work on plaster that has since been painted.

Roughcaster.

 

[noseall]

Blisters are due to a lack of suction which is a direct result of a dense backing coat that has not hydrated.Whilst water is still trying to escape from these products then skimming them at this stage is a no-no.

Thistle (carlite) bonding and hardwall are typical examples of backing coats that should not be skimmed too soon.

These should be rubbed up, scored or keyed and left to go off.

 

[roy c]

I some times get them when I have laid the "first" coat on a bit thick in places and am putting the second coat on , so I just brush the bubbles out with a dryish brush and put the rest of the second coat on and come back and trowel the brush marks out then flatten, but still have to leave it till final trowel.....