Hi folks,

We've had a wood burning stove in our extension for about 4years. Over
that time a strange pattern of stains has formed on the ceiling,
whereby dark spots are present wherever a screw was positioned to hold
up the plaster boards.

I'm not sure if this is smoke damage, which would be weird if it
produced such a regular pattern, or if the plaster board screws are
somehow bleeding through.

Any ideas on a likely source, or thoughts on how treat it and stop it
happening again would be greatly received.

Matt