Mould on exterior surfaces

Problem - Mildew on exterior surfaces
Black or brown spots and areas occurring on finished or unfinished surfaces.

Possible causes

  • Humid, warm autumn and winter.
  • Mould normally occurs on damp surfaces with little or no direct sunlight.
    North-facing walls and eave soffits are especially susceptible to mould.
  • Mould was not completely removed from the surface or paint coat before painting.
  • The plinth is too low.
  • Nearby vegetation, such as organic impurities from trees.
  • Inadequate preparation.


If the surface does not require repainting, remove mould with Tikkurila Huoltopesu (Maintenance Cleaner) as instructed on the product label and rinse thoroughly.

If the surface is to be repainted, remove mould with a solution of Tikkurila Homeenpoisto (Mould Removal), 1 part to 3 parts water.

Protect yourself and your plants, glass surfaces, etc. from splashing.
Clean with a sponge or a soft brush. Wash larger surfaces with a portable sprayer.

Spray the solution upwards to avoid seeping or streaks. Let the solution take effect for about 30 minutes. Surfaces badly affected by mould should be left wet until removed completely. Wash from the top downwards using plenty of water.

Allow to dry. Apply primer undercoat to the clean wooden surfaces. Paint with a suitable Tikkurila exterior paint according to instructions.