Dust, dirt, air-borne salt build up on wall surfaces


Atmospheric conditions


Almost all exterior wall materials and finishes will last longer and look better if they are cleaned regularly. Cleaning removes contaminants that can hasten deterioration.

  • Wash down the exterior of the building at least once a year. Use a low-pressure hose, a soft brush and a gentle detergent and rinse thoroughly. If detergent is not sufficient, use a solution of 1 part household bleach to 4 parts water then rinse thoroughly. If using bleach, wear safety glasses and protective gloves and clothing. Do not let wash-water containing bleach enter garden beds or a stormwater system.

  • Do not use a waterblaster on weatherboard walls – it can lead to long-term damage if it forces water through gaps into the wall assembly. Do not waterblast old fibre-cement walls that may contain asbestos. Waterblasting can be used on exterior concrete.

  • Increase cleaning frequency to 3-monthly in geothermal or severe marine areas. 

  • Where unpainted steel cladding is used, wash down areas not rain-washed at 6-monthly intervals. 

  • Clean glass every 3–4 months, more frequently in severe marine areas.

  • Make cleaning the exterior part of a regular maintenance programme – see Maintenance Schedule for details


Lack of rain washing or lack of washing by owner


  • As for the repair above.