Many painters and DIY customers believe the best way to prepare a surface for painting is to water-blast and in many situations they are quite right - but not when it comes to joinery and timber weatherboards.

Protect your paintwork with Resene Paint Prep and Housewash
We are regularly asked for advice on cleaning weatherboards. Generally when you are planning to repaint, weatherboards will be dirty and weathered and need cleaning. We recommend washing with Resene Paint Prep and Housewash as waterblasting isn’t as effective and can damage the woodwork.
That’s why we developed Resene Paint Prep and Housewash to loosen and shift the chalky surface on UV damaged paint films. The ‘chalk’ is the unbound pigment in paint and must be removed along with other contaminants, including dirt, and moss and mould before painting.
Waterblasting doesn’t shift this chalk (dechalking).
Additionally, Resene Paint Prep and Housewash:

Mix ratio of 1:4 parts of fresh water

Before washing
The following photos demonstrate how it works:

Rinse the area to be washed

Wash the weatherboards and windows - a smaller brush/3M scouring pad are ideal for corners etc

After washing
See the Resene Caring for your paint finish brochure for further cleaning recommendations.