Brown Circles on skimmed plasterboarded walls

[cmacca75]

I have recently had some walls plasterboarded and skimmed, I left them to dry for around 4 weeks, when i returned i noticed some football size dark circles on all the walls, I have just given one wall 2 mist coats with white emulsion 50-50 then 75-25, I could still see the marks through that so i have just done one more coat with dulux once and its still the same. Does anybody know what these circles are? and how can i get rid of them?

 

[TheDec]

You can avoid their return by applying a thinned oil based undercoat over the areas prior to your emulsion, and you could ask on the Plasterers forum to try and determine the reason why they exist.

Dec

 

[peterperfection]

You can avoid their return by applying a thinned oil based undercoat over the areas prior to your emulsion, and you could ask on the Plasterers forum to try and determine the reason why they exist.

Dec

Plasterboards will have been 'dabbed on' to walls-possibly/probably with ordinary plaster instead of 'dry lining adhesive'.
Dabbing on with ordinary plaster takes ages to dry properly-if applied pretty thick-much slower than the correct stuff..

 

[TheDec]

Yes perhaps, but we really dont know how the plasterboard was installed do we.

Dec

 

[peterperfection]

Yes perhaps, but we really dont know how the plasterboard was installed do we.

Dec

It's easy to tell. Just tap (with your knuckles) the places with the brown circles and then tap the places a few inches away. Brown circle places will have a 'solid sound' on tapping them-- and other places without the circles will sound hollow .

 

[TheDec]

Thats all very well and good, and at this moment of time I dont doubt that you are right. That is why I asked the op to make further enquires on the plasterers forum.Dec

 

[peterperfection]

Thats all very well and good, and at this moment of time I dont doubt that you are right. That is why I asked the op to make further enquires on the plasterers forum.Dec

It's ok and I understand. It's sensible advice too.
I can only add that I have done mega loads of plastering myself and have employed and sacked mega loads of plasterers for using incorrect materials and sloppy penny-pinching work.
A bag of 'thistle costs half the price of a bag of dry wall adhesive .

 

[cmacca75]

Thats all very well and good, and at this moment of time I dont doubt that you are right. That is why I asked the op to make further enquires on the plasterers forum.Dec

It's ok and I understand. It's sensible advice too.
I can only add that I have done mega loads of plastering myself and have employed and sacked mega loads of plasterers for using incorrect materials and sloppy penny-pinching work.
A bag of 'thistle costs half the price of a bag of dry wall adhesive .

Peter you were correct, the patched areas are solid sounding when knocking them and the other areas are hollow.

 

[TheDec]

So providing the stained areas are dry you should be fine to apply your oil based undercoat, or to be certain that these areas dont at a later date come back and haunt you you may wish to substitute the undercoat for an Alkali resistant primer.

Dec

 

[cmacca75]

So providing the stained areas are dry you should be fine to apply your oil based undercoat, or to be certain that these areas dont at a later date come back and haunt you you may wish to substitute the undercoat for an Alkali resistant primer.

Dec

Thanks for your help Dec, I will go and buy some tomorrow and give it a go.