How To Get Rid of Mold on Exterior Walls

Henri Bauholz

Mold needs to removed from an exterior wall to keep a large buildup from occurring, which over time could cause some structural damage to your home that is difficult and expensive to repair.

A good time to remove mold is just before you paint your house, for the exterior needs to be cleaned to ensure that a good adhesive coat of paint is applied to the exterior surface. However, if a heavy mold buildup is present, you may have to immediately remove the growth as a preventive measure.

  1. Scrub any visible areas of mold with a long scrub brush that has a sturdy wooden handle. Inside a plastic 2-gallon pail, prepare a mixture of liquid soap, liquid bleach and water. The bleach should be less than 10 percent of the overall mixture while the soap should be less than 5 percent of the overall solution.

  2. Rinse the area that you just scrubbed with a hose.

  3. Go over any difficult to clean areas with a hand brush and an identical mixture of soap, bleach and water. This may entail climbing on a step ladder or an extension ladder. Pay particular attention to the wooden trim and the soffits that lay directly underneath the edge of the roof. Also, look for places where air circulation is at a minimum since these are also prime locations for the build-up of the unwanted fungus.

  4. Go after any affected area that does not come clean with a paint scraper and wire brush. If you are working on the exterior of a building it is almost always advisable to work down to bare wood if necessary.

  5. Again hose the area where you have been cleaning and scraping. Do this before you cover the treated area with painter or sealer.

  6. Rent a power washer from a reputable rental store and used the high-powered stream of water, soap and bleach to thoroughly clean the side of the house. These machines are frequently used by homeowners and contractors, alike, to prep the exterior walls of a house or building before painting. Washing the side of a house with this pneumatic tool is a two-step process. Wash and rinse. Please follow the manufacturer’s guidelines for soap and rinse procedures. Always start on the back of the house, so you can become familiar with the power of the machine and be able to set the power stream so that it does not create huge debits and gouges in the exterior covering.

  7. Clean any heavily affected area with a mixture of bleach, water and trisodium phospate (TSP). Mix 1/4 cup of TSP and 1 cup of bleach to every 2 gallons of water. This mixture not only cleans but dries out the wood slightly and thus serves as a preventive measure against the return of the mold. Then rinse the clean area with fresh water.

  8. Tip

    Choose a time of prolonged fair weather to remove the mold and clean the affected areas.


    Any wood replacement to the structural frame of the house that needs to be done, because of a severe and advanced progression of the mold should be done as soon and thoroughly as possible.