I've got spots on my ceiling in one of the bathrooms in my house. There are 3 spots in a straight line. They are perfectly round and very small. I am thinking they are the nail heads as magnets stick to them. The spots are cold and seem lightly damp. I am thinking it is condensation on the nail heads as they must act as a conduit for the cold to come in from the attic.

How can that be fixed? I cleaned my bathroom fan and I think it's about 15cfm under the HVI recommendations. It was very dirty, so I don't know if maybe it's not drawing out enough humidity from the air?

What should I do?

  • What do you mean by "fixed"? Do you just not want to see them anymore?
    – CactusCake
    Jan 15 '18 at 22:08
  • Yes, I don't want to see them anymore.
    – John Arg
    Jan 15 '18 at 22:09
  • Is there some reason why painting over them would not be sufficient?
    – CactusCake
    Jan 15 '18 at 22:10
  • 1
    If they are indeed nails, then the returning discoloration after painting may be from corroded metal leeching into the paint while it's still drying. You'll need to either replace the nails with something that's a bit less reactive with water (like brass or stainless steel), but they could be tricky to remove if they've been sunk flush with the ceiling. Instead, you could use a punch to drive them a little bit deeper, then fill the resulting crater with plaster or vinyl spackling, then paint. That would distance the paint layer from the metal a bit, hopefully enough to prevent staining.
    – CactusCake
    Jan 15 '18 at 22:18
  • 1
    Drywall screw locations are often also the first place a roof or plumbing leak shows itself. Water runs until it finds a way thru.
    – Tyson
    Jan 16 '18 at 0:05

The nails penetrate the ceiling and some insulation so they get cold enough for condensation to form. This leads to both rust and mildew by the heads.

Before you clean up the rust and/or mildew, replace any insulation above the bathroom that may have been damaged and add additional insulation above the joists to prevent a recurrence.

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