bwiechman

After this last winter the nails in the drywall on my exterior walls are all discolored. I can see pretty much all of them, especially near the ceiling and on the NW side of my house.

My house is an old school house that was remodeled about 20 years ago. There is about 5 feet of dead air space above my ceilings that definitely needs better insulation. The walls are all insulated (I believe), but there really isn't anything to stop the air from the dead air space above my ceiling from moving down the wall cavities.

Is the discoloration likely due to condensation from that cold air coming down the wall cavity from above the ceiling?

What can I do to fix that - spray foam I am guessing would be one possibility as this would insulate the walls better, and also serve as a better vapor barrier. Any other method?

inspectorD

The likely cause of your "ghosting" nails which show is from soot.
Either you burn candles, smoke or your fireplace is not drafting correctly. This is caused just as you said, by warm air carrying the soot across the cold nail in the wall. The soot collects on the cold nail. The worse it gets the more you see, eventually you will see the studs in the walls because they are colder due to the extreme temp variations.
Insulating won't help much unless you insulate across the faces of the studs to help control the temp difference.

Hope this helps , I know when I first saw this I was confused also.

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handyguys

What he said ^^^

You may just want to see if the paint is decent enough quality to allow you to wash your walls. Just a bucket of warm water and a mild detergent such as spic and span or TSP. May also try a little bleach in the water. Make sure your cleaner doesn't contain Ammonia if you add bleach.

Let us know if it doesn't wash off. if its a bleed through of the nail you may have other issue.

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