Bathroom ceiling zits

[gillstone]

Our main bath has little brown spots on the ceiling. The spots line up with where the drywall was nailed in.  They do wipe away easily, but reappear in the same spot within a few weeks.  Once they appear they do not get bigger or spread to other areas.  Bathroom ventilation is good and no smokers have lived in the house for at least a decade. The bathroom was completely remodeled by the prior owners about 4 years ago. 

I've heard a dozen different theories, but they all involve different fixes so I'm hoping for some clarity so I know if this is an issue and how much work it will take to deal with if it is an issue.

[Jack]

(Disclaimer: I am a DIYer with no professional knowledge about paint.)

It sounds to me like your nailheads are rusting... but the real questions are "why are they rusting?" and "what do you do about it?"

First, check that there's not excessive humidity in the attic or something (or a roof leak).

If the attic checks out OK, try spackling over the spots (if necessary), spot-priming with a stain-blocking primer, and painting the whole ceiling with paint that's either one grade glossier than you had before (e.g. if it was flat, use eggshell) or "kitchen and bath" paint.

[Greg]

If the spots wipe away easily they could be rust-related, but also could be condensation-related.  The nail or screw heads are a direct connection to the rafters or joists above, and therefore conduct more heat/cold.  Humid air from bathroom activities hits the spot over the screw/nail head and water forms, often collecting dirt from the air and surface to color it brown.  Left long enough the spot will become a drip if this is the case.  Either way you could have a moisture and/or ventilation issue.  A timer bath fan is a good way to help with ventilation.

You mention no smokers in the last decade, but nicotine and other side-effect of cigarette smoke can really get into surfaces.  If you want to try an easy solution, try coating the entire ceiling with an expensive stain-blocking primer, and fresh paint, gloss or semi-gloss.  This may seal in the smoke residue of that's the case.

[gillstone]

Thank you

After reading "IT'S MOLD! BURN THE HOUSE DOWN WHILE YOU STILL HAVE TIME!!!" on so many forums where questions like this get posted, I really appreciate an answer that makes sense and doesn't start with pants-crapping panic.

[Outlier]

I've fixed that in a few houses and it's really common. It's the humidity from showering causing rust on the nails or screws the hold the drywall. Make sure the bathroom vent is working well since that will help with the problem. If your not comfortable with doing a little drywall repair you can hide it with paint for a while.

To hide it with paint wipe down the ceiling, prime it with two coats of killz primer. Then paint it a color other than white. That will hide the issue for a while.

To fix it you need to get an exacto knife and dig out one of the spots to find out if it's a nail or a screw. Nail heads rust and pop way worse than screws. If it's a nail pull them one at a time and replace them with coated drywall screws. If it's screws just replace the screws with new coated drywall screws. Then add a few more since you just trashed the ceiling anyway to get the screws replaced. Added support never hurts.

Then you patch all the spots with all purpose drywall mud sand prime and paint.

It's a pain but I always do that in bathrooms that have nail pop spots.

[gillstone]

Update!

I already had the Killz primer with bath/kitchen paint on the ceiling, so I looked into my bathroom fan and found all sorts of issues with it.  This is a basement bathroom with a non-functioning window and a jetted tub.  The fan in place was a standard 70 CFM fan that was ducted for over 6 feet to reach a hole 9 inches directly below the fan.  The doglegs and loops it went through were insane.  I yanked hat all out and dropped in a 180 CFM monster of a fan that is the same noise level as the old one.

I can see steam getting pulled through the fan when I run it and my bathroom will barely get foggy now.  The zits wiped off the ceiling easily and none have returned.   

[Greg]

Thanks for the update.  Sounds like you figured out a good solution.

I do residential design/build... wouldn't install anything less than 80CFM, the quieter the better!