How To Control Mildew

Mildew is a product of mold fungi. It manifests itself with a gray or black discoloration, or sometimes a reddish coloration as well. Mildew is responsible for many problems in the home including allergies and asthma. If left untreated, it can contribute to dry rot and destroy paint finishes. Mildew grows best in a warm, moist atmosphere on a nutrient-rich surface. While in times past, mildew was less of a problem for homeowners, the new green mantra promotes the growth of mildew by requiring that homes be built to tighter standards. This means that we must be more proactive in killing mildew and keeping it away by making certain changes in how we live in our homes and how we maintain them.

Killing existing mildew with cleaning solutions

Mildew damages surfaces and finishes but it can be controlled

Mildew damages surfaces and finishes but it can be controlled

  1. Before you can repaint or refinish any wood surface, you must completely kill any mildew that exists on that surface or it will simply grow through the new finish.
  2. You can use one part of bleach to three parts of water and include ΒΌ cup of liquid dish detergent.
  3. Wash the surface thoroughly using a scrub brush, if necessary.
  4. Let the solution sit on the surface for at least ten to fifteen minutes.
  5. Rinse the solution and any loose dirt or mildew off with cool water.
  6. Make sure the surface is completely dry before applying any finish material.
  7. You can also use a sodium percarbonate product that is safer to use than the above bleach mixture. Apply it in the same manner though, letting it sit on the surface for at least fifteen minutes before you rinse it off.

Killing mildew with chemical solutions

  1. You can apply a mildewcide to surfaces that need treatment.
  2. Be sure to follow the manufacturer’s instructions and let the mildewcide sit on the surface for the prescribed period of time to ensure complete killing of the mildew spores.
  3. Use a paint primer like Kilz that will prevent the growth of mildew.
  4. Apply the finish coats with a paint that includes a mildewcide. If you buy a paint product that does not contain one, you can have the paint store mix in some mildewcide before they shake the paint.
  5. Oil based paints work best, especially semi-gloss or gloss oil based paints and enamels because you can wash those surfaces and keep the mildew away.

Mildew prevention

  1. Since mildew needs warm, moist air to survive along with a nutrient-rich surface you can take steps to help minimize or even eliminate mildew in your home.
  2. Increase ventilation to humid areas like bathrooms by leaving the door open after a bath or shower.
  3. Install and use a bathroom vent fan if there is not one in your home. Make sure it is sized correctly so that it exchanges the air in the bathroom the proper number of times per hour. You can find this information by consulting your local building and codes department.
  4. Open windows when possible to cool down the room.
  5. Use portable fans to move the air around and help cool down the rooms in hot weather.
  6. Keep surfaces clean and dry.
  7. Close the shower curtain after each shower.
  8. Replace grout and caulk that has mildew growth. Simply cleaning these will not remove or kill the mildew. It will simply grow back again.
  9. Make sure your crawlspace is properly ventilated, including a proper vapor barrier on the ground and insulation between the floor joists.
  10. Be proactive in removing mildew promptly. You may even have to replace certain surfaces that have been contaminated.


It is impossible to completely remove mildew as an irritant and microbial pest but it is possible to control it. Just take the necessary proactive steps to kill it where it is evident and maintain the proper environment to discourage its growth.

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