Painted timber weatherboards – bubbling or blistering of paint

Cause

Loss of adhesion due to excess moisture in substrate

Repair

  • follow the preparation and repainting guidance for the first repair. After scraping and removing loose paint, pay particular attention to any joints, gaps, cracks or splits in the weatherboards. Ensure they are primed and/or filled with flexible filler as appropriate before painting – follow the product manufacturer’s guidance.

Cause

Poor initial substrate preparation

Repair

  • follow the preparation and repainting guidance for the first repair. Be careful with preparation, ensuring the substrate is completely clean and dry before painting begins.

Cause

Oil-based (alkyd) paint applied over water-based (latex) paint

Repair

  • oil-based paint should generally not be applied over water-based paint. To determine whether an existing paint finish is water-based or solvent-based:

    • soak a cotton ball in rubbing alcohol (isopropyl or ethyl alcohol), an acetone-based nail polish remover or lacquer thinner]

    • rub it over a small, inconspicuous section of wall

    • if paint comes off, it is water-based; if unaffected, it is a solvent-based paint

  • follow the preparation and repainting guidance for the first repair. Apply at least two coats of good quality high-gloss or semi-gloss water-based paint.

Cause

Surface was damp or dirty when painted previously

Repair

  • follow the preparation and repainting guidance for the first repair. Be careful with preparation, ensuring the substrate is completely clean and dry before painting begins.

Cause

Dark colours increasing surface temperatures 

Repair

  • follow the preparation and repainting guidance for the first repair. Scrape/sand off all the old dark-coloured paint. Repaint with a good quality high-gloss or semi-gloss acrylic paint in a light colour. Darker colours attract heat, which can cause greater expansion/contraction of the timber, and thus a reduced lifespan for the paintwork.

Cause

Timber swelling/shrinkage caused by moisture absorption into timber end grain if joints were not adequately primed before installation

Repair

  • follow the preparation and repainting guidance for the first repair. After scraping and removing loose paint, pay particular attention to any joints, gaps, cracks or splits in the weatherboards. Ensure they are primed and/or filled with flexible filler as appropriate before painting – follow the product manufacturer’s guidance.

Cause

Water-based paint coat exposed to moisture before paint has fully dried

Repair

  • follow the preparation and repainting guidance for the first repair.