First, it has to be very clear that until the source of the water is addressed and corrected, nothing you do will last very long. In other words, solve the problem (leaky roof or windows) before addressing how it manifested.
I often approach these situations by looking at the overall severity of the mold. It’s important to understand that some mold strains are very toxic and with that comes some liability – you touch it, you own it –so if it’s more than you would be comfortable with, refer it to a professional remediation company. If there is mold behind the drywall, then structural removal is required. This includes insulation, framing and plywood sheathing. Any other involved surface would have to be remediated as well. Determining superficial versus structural is really important.
Surface mold can be remediated pretty easily with simple methods. You don’t want to release a bunch of mold spores into the air, so the first step would be to set up containment. You can do this with plastic and a negative air environment. You can spend thousands on fans, ducting and HEPA air scrubbers, but for most painters this is overkill – a plastic barrier with a couple of box fans exhausting will suffice. Vacuum the surface mold with a brush attachment on a HEPA vacuum, and then treat the surfaces.
There are many over-the-counter solutions you can buy; one that is readily available in stores is Concrobium. There are also household items that will kill mold, such as white vinegar and baking soda, hydrogen peroxide 5% solution to distilled water, and Borax.
After you have treated the areas, allow the solutions to sit on the surface long enough to work, and then wipe with a clean damp cloth. Put a fan on the area and allow it to dry completely before priming. I prefer Zinsser B-I-N for this, but there are lots of good primers that could also work. Once you get to primer stage, paint as usual.
Tommy Johnson - Johnson Home Construction - Wallace, NC.