Paint coatings do not last forever, and cleaning and recoating must be carried out regularly to keep a house weather-resistant on the outside and looking good outside and in.

How long exterior paint will last depends on the:

  • quality of surface preparation
  • quality and condition of previous paint – new paint will last longer if the old paint is still in reasonably sound condition when repainted
  • quality of paint
  • amount of sun (UV) exposure – paint on the south side of a building will last longer than paint on the north or west side
  • colour – lighter colours tend to last longer than darker because they absorb less heat, so expand and contract less
  • size and type of material under the paint. For example, paint on wide timber boards may not last as long as on narrower boards because the overall movement in the boards is greater. Paint on cement-based materials (concrete, cement plaster, fibre-cement) tends to last longer than paint on timber
  • cleanliness of the painted surface – painted surfaces last longer when they are washed down regularly to remove dirt and airborne chemicals from the paint surface
  • number of coats applied
  • underlying colour – applying a dark colour directly over a light one can sometimes cause a previously sound paint to lose adhesion because of the higher surface temperatures.

For interior surfaces, the need for painting is usually motivated by the desire to change the appearance rather than replacing failing paint. Internal paint or clear finish failure is possible, however, particularly:

  • where exposed to high amounts of sunlight/UV, such as along window sills
  • in wet areas such as steamy bathrooms
  • on fibrous plaster surfaces
  • on masonry internal walls that have absorbed moisture.
Checking paint condition

The first signs of paint failure in timber are usually at the corners (where the coating is thin) and at joints, mitres or ends where moisture has been absorbed.

Other common failure modes are:

Failure

Cause

blistering

  • trapped moisture in the substrate
  • resin bleed in timber
  • heat source too close to the paint

chalking

 

  • UV weathering

cracking

  • recoating before the earlier coat was dry
  • a hard coating applied over a soft elastic coating
  • movement in the substrate

peeling/flaking

  • unsound surface
  • wrong paint for the substrate
  • incompatibility with the previous paint coating
  • too long a time left between coats
  • the surface was damp when painted
  • poor adhesion between coats
  • dark-coloured exterior paint applied over light.

 

To test how well a paint is adhering, select an area of paint not too visible, then make criss-cross cuts (#) in the paint with a sharp blade. Press adhesive tape over the cuts, then pull the tape off. If paint flakes come off with the tape, the paint should be removed before repainting. If the existing paint is firmly attached, new paint coats can be applied after a thorough cleaning and light sanding. It is good practice, however, to remove all existing paint at every fourth or fifth repaint.