Earth construction – bubbling or blistering surface finish
Causes
Loss of adhesion due to excess moisture in substrate
Poor initial substrate preparation
Oil-based (alkyd) paint applied over water-based (latex) paint
Surface was damp or dirty when painted previously
Dark colours increasing surface temperatures
Water-based paint coat exposed to moisture before paint has fully dried
Listed under: Exterior, finishes, paint, cladding, walls, moisture, wall cladding, earth construction
Cause
Loss of adhesion due to excess moisture in substrate
Repair
- consult an earth building specialist
- if blistering goes through to the substrate, it indicates that there is a high moisture content in the plaster and this must be addressed before repainting
- scrape and/or sand off loose paint; clean until surface is sound; allow to dry thoroughly; prime; fill joints with exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint suitable for the plaster finish
- There are three New Zealand standards covering earth building. Updated versions of each were published in February 2020:
Cause
Poor initial substrate preparation
Repair
- consult an earth building specialist
- if blistering goes through to the substrate, it indicates that there is a high moisture content in the plaster and this must be addressed before repainting
- scrape and/or sand off loose paint; clean until surface is sound; allow to dry thoroughly; prime; fill joints with exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint suitable for the plaster finish
Cause
Oil-based (alkyd) paint applied over water-based (latex) paint
Repair
- consult an earth building specialist
- if blistering goes through to the substrate, it indicates that there is a high moisture content in the plaster and this must be addressed before repainting
- scrape and/or sand off loose paint; clean until surface is sound; allow to dry thoroughly; prime; fill joints with exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint suitable for the plaster finish
Cause
Surface was damp or dirty when painted previously
Repair
- consult an earth building specialist
- if blistering goes through to the substrate, it indicates that there is a high moisture content in the plaster and this must be addressed before repainting
- scrape and/or sand off loose paint; clean until surface is sound; allow to dry thoroughly; prime; fill joints with exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint suitable for the plaster finish
Cause
Dark colours increasing surface temperatures
Repair
- consult an earth building specialist
- if blistering goes through to the substrate, it indicates that there is a high moisture content in the plaster and this must be addressed before repainting
- scrape and/or sand off loose paint; clean until surface is sound; allow to dry thoroughly; prime; fill joints with exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint suitable for the plaster finish
Cause
Water-based paint coat exposed to moisture before paint has fully dried
Repair
- consult an earth building specialist
- if blistering goes through to the substrate, it indicates that there is a high moisture content in the plaster and this must be addressed before repainting
- scrape and/or sand off loose paint; clean until surface is sound; allow to dry thoroughly; prime; fill joints with exterior grade flexible (polyester) filler; paint with a minimum two coats of semi-gloss or high gloss acrylic paint suitable for the plaster finish