Paint spots over edge of plaster walls over metail strips

[GMorton]

We have just completed an extension. The interior walls have been plaster boarded and plastered. On the edges under the plaster are metal strips which the builder said stopped the plaster from shrinking.

We sealed the plaster and have applied a 3 coats of paint. Each time there are spots in the pattern of the metal strips appearing on the painted surface. They look light wet paint but are dry.

We have tried re sealing with PVA and painting over but the same happens. Does anyone have any other suggestions.

 

[joe-90]

Could be rust. Try an oil based primer or undercoat.

 

[Zampa]

They could indeed be rust as Joe says or..if they are paler than the painted wall...a reaction between the bare plaster and the zinc coating on the strips..

Go over them with oil based undercoat..and give the PVA a swerve..

 

[Robbie uk]

Dont think the plaster can shrink can it ?? its an inert substance, maybe someone will tell me different. Other surfaces around it are usually what shrinks.

 

[Zampa]

I was a bit surprised reading that too..but I spose the water must go somewhere when it dries..hence slight shrinking maybe?

Tiny amounts though..microns..(however big they are )