Any ideas on why this one outside door may be growing what appears to be mold around the doorknob?

It doesn't happen on any other outside doors (or on the inside of this door) and after painting over it a couple of years ago, it's come back. Cleaning it off also seems impossible (have tried scrubbing w/ various things and nothing comes off).

Seems odd that it'd only happen to this door, but ultimately I just want to get rid of it and have it not come back.

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I would temporarily remove the door latch hardware (i.e. door knob and deadbolt) and then use a hand sanding operation to remove the old layers of paint and black stains (i.e. mold and old hand oil prints) down to clean base material.

As you have noted the staining is very good at telegraphing through paint layers and so the only real way to remove all of that completely.

You will want to use care with keeping the sand paper grit fairly fine at the last stages as you get to the base material. This will apply to both vinyl clad and exposed wood frame doors. After sanding it would be a good idea to clean the area with a bleach solution. After dry paint the area with a good quality primer. Use care with the application of the paint to blend the edges up to the unsanded areas to ensure that there is no visible ridge at the paint edge.


The mold is feeding on the oils from fingerprints. You can see the pattern where many hands over many years have pulled on the door. It looks like a vinyl covered door, so should be easy to clean.

  • Definitely not easy to clean...in fact nothing I've tried makes any dent in cleaning it. It's been painted multiple times and the mold just comes back. – Shpigford Dec 5 '20 at 15:16
  • Then you have to kill it first. Cut a strip of towelling and duct tape it to th area. Remove the lock hardware first and maybe put tape over the exposed holes. Soak the towelling with 50% bleach and water. Tape some towelling below the area to catch drips. Keep the towel wet all day so the bleach can be absorbed deep. Then remove and wash normally. Right now I can't think of a top coat. – John Canon Dec 5 '20 at 15:27

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