What should I do about this possible mold I found under paint?

Question

I live in Austin, Texas, which is important in that we don't receive much rain, and it's not very humid.

I was peeling paint off of the old drywall, and found what appears to be mold on the bottom of one of the exterior walls of my room. Some of it is beneath a window, but some is offset two feet or so on the other side of the same window.

Some of it coincides with what I believe to be old termite damage. It's clearly been patched, and the infestation is definitely inactive.

My suspicion is, since it's an old house, that there is no vapor barrier, and the mold is the result of condensation. I suppose it could also come from a leak in the window. The previous homeowner blew in insulation, and my understand is that without a vapor barrier, that can cause some condensation problems.

Is it worth it for me to just tear out the drywall, add a vapor barrier along just the one side of the room, and then insulate it? Or should I use some bleach to clean up the mold damage, cover it over with some Kilz, and paint?

The damage is clearly old -- probably around a decade. But now I'm thinking, well, I've got the paint off the wall, might as well. But I also have a tendency to take projects too far, so I could use a second opinion.

Answer 1

IMO you are making several leaps here that don't fit. You've got mold below a window, spread out about 2 feet on either side, and you suspect condensation as the culprit.

You specify that the damage is old - years old by the look of it. Condensation happens every year, every season. Why would the damage be old, it should be fresh if it's condensation.

Finally - if condensation were the culprit, the condensation and thus the mold would be uniform. Water leakage through a window, however, is going to fan out below the window in both directions...

The answer is your window leaked at some point - years ago by the sound of it since the damage is old.

Solution?

Remove and replace ONLY the section of drywall that is damaged. Do not add a partial vapor barrier as that's about as useful as putting in an aquarium with only 2 sides. Mud and tape properly and repaint.

Answer 2

I would say it is definitely a leak around your window pane, and as the answer above suggests, if it was down simply to condensation, then the mold would, indeed, be uniform.

I would say fill any gaps in the window, then damp proof the area with the mold with damp proof paint.

Then keep an eye on it and if it continues then get in some experts.

Oh yes, be sure to also get a dehumidifier to completely remove all humidity in the roomn too.