Black, green, grayish, or brown spots on a painted surface may be mildew. One test is too slightly dab an area with bleach; if it turns white then it is usually mildew, if it stays dark, then it is probably dirt.
Mildew is basically a form of fungi feeding on the nutrients in the paint or dirt.
Common Areas for Mildew to Develop
The growth of mildew is associated with moisture and shade. Areas that receive a lot of sunlight are less apt to develop mildew that shaded areas. Window sills, gutter and downspout areas, under eaves, areas shaded by shrubbery and the north side of the building are prone to developing mildew.
Cleaning and trimming back shrubbery
A light scrubbing with a gentle cleaning solution will generally handle mildew on paint. Allowing more light and sunshine to the mildewed areas will also help. Trimming back trees and shrubbery is often recommended.
When repainting using a specially formulated “mildew-resistant” primer and finish coats will help reduce or prevent mildew from developing.
Who to consult? Painters and qualified handymen.
Home owners will often handle many painting jobs around the house, both inside and outside. Handymen and painters will also handle painting tasks. Normally painters are the most proficient, knowledgeable and quickest at doing painting task.