Wiped and painted - Yellow stains?!

Hello,

I have a huge problem and unfortunately currently see no solution, hope you can help me.

We bought an old farmhouse built in 1890, we installed battens on the old timber-framed walls and then closed the walls with OSB boards from the hardware store, then we consulted a local plasterer on how to treat the boards so that we can apply roll-on plaster directly on them, based on his advice we painted a primer and let it cure for a week. Then we applied the plaster; already after about 12 hours many small yellow spots became visible. We have now tried to paint the primer several times but even after applying it four times there are still spots in the plaster.

We then had a representative from the company come and applied a blocking paint, which unfortunately was also ineffective.

After another visit by a representative, we received an insulating agent and treated a spotted wall with it, but unfortunately this agent was also useless.

What can be done? I actually don't want to paint everything five times again or so. I suspect that the resin from the boards is what is causing the spots because we installed a new beam which I treated the same way and with it two knot holes seem to show through the plaster.

Please help

Many thanks in advance

Hello,

you have quite a little problem there.

I have a few questions before I can form an opinion.

Which barrier primer was used? (Water-based, alkyd resin?)
Which type of plaster was used? Silicate, synthetic resin, or glue/lime plaster?
Which insulations were possibly added later?

Please provide, if possible, which products and qualities were used.

It may be that when barrier materials are used incorrectly, the ingredients can still penetrate if the components are not compatible with each other or not intended for such use.

If possible, take photos.

Regards
Igor

P.S.
Please excuse any spelling mistakes. I don’t pay much attention to that.

Hello Meli,

either screw GK/GF boards onto the OSB boards or plaster base coat, mesh, top coat. Otherwise it won't work (stains, cracks, etc.)