Unpainted wood: In damp, warm, poorly ventilated areas, surface mold often develops on wooden parts of buildings. Since new, unseasoned lumber is particularly susceptible to mildew, avoid using it whenever possible.
Painted wood: Indoor wood surfaces covered with enamel or oil-resin paint rarely mildew. Softer paints on outdoor surfaces mildew more readily. Molds feed on the oil and minerals in the paint and cause a dirty-looking discoloration. They may penetrate the paint film deeply, even to the underlying wood.
If your wood has already begun to form mildew, use heat and increase the air circulation to get mildewed wood as dry as possible. Badly infected wood may need to be replaced, preferably with wood that has been treated or that is naturally decay-resistant.
Tip: Mildew-resistant paints in all colors for outdoor wood surfaces are available at paint and hardware stores. Manufacturers have suitably formulated their products with fungicides to help combat mildew attack.