Plywood cladding – bubbling or blistering paint/stain

Cause

A loss of adhesion due to excess moisture in the substrate

Repair

  • scrape and/or sand off loose paint; sand bare timber until the surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint
  • if blistering goes through to the substrate, it indicates that there is a high moisture content in the timber and this must be addressed before repainting.

Cause

Poor initial substrate preparation

Repair

  • scrape and/or sand off loose paint; sand bare timber until the surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint
  • if blistering goes through to the substrate, it indicates that there is a high moisture content in the timber and this must be addressed before repainting.

Cause

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

Repair

  • scrape and/or sand off loose paint; sand bare timber until the surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint
  • if blistering goes through to the substrate, it indicates that there is a high moisture content in the timber and this must be addressed before repainting.

Cause

Surface was damp or dirty when painted previously

Repair

  • scrape and/or sand off loose paint; sand bare timber until the surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint
  • if blistering goes through to the substrate, it indicates that there is a high moisture content in the timber and this must be addressed before repainting.

Cause

Dark colours increasing surface temperatures 

Repair

  • scrape and/or sand off loose paint; sand bare timber until the surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint
  • if blistering goes through to the substrate, it indicates that there is a high moisture content in the timber and this must be addressed before repainting.

Cause

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

Repair

  • scrape and/or sand off loose paint; sand bare timber until the surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint
  • if blistering goes through to the substrate, it indicates that there is a high moisture content in the timber and this must be addressed before repainting.

Cause

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

Repair

  • scrape and/or sand off loose paint; sand bare timber until the surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint
  • if blistering goes through to the substrate, it indicates that there is a high moisture content in the timber and this must be addressed before repainting.