I have purchased a house built in 1911. I have removed some paneling that had been nailed over plaster walls in two of the bedrooms. There is mold on the plaster where each panel touched the next and then it kind of fans out under the panels in places. The paneling was some kind of drywall, about 15 inches wide and not sealed. The problem is on the outside walls. I want to put dry wall up rather than patch the plaster. I am afraid that the same problem will occur if I do that. How do I prepare the surface before I put up the drywall so I prevent future problems?

 

I would first discover the source of the mold. Check for water leaks, etc. If the source is not determined, and its an active source of moisture, the mold will always return.

As for the walls, wash them with a bleach/water mix, and seal it with an alkyd primer to lock in any residual mold. Then proceed with the new drywall.

As a professional, I have learned if I encounter any growth of mold over 10 sq. ft., I must advise the customer to call an industrial hygienist, or contact the local health department and ask them about mold abatement procedures for that particular county. Way too many legal issues concerning mold these days.