Painted timber weatherboards – paint failure at base of walls

Cause

Cladding covered by soil/foliage

Repair

  • remove soil/foliage covering cladding
  • if any of the timber is rotted, cut it out and replace it with new treated timber. Aim for at least a 50 mm gap between the bottom of the cladding and the ground or paving to prevent moisture uptake
  • scrape and/or sand off loose paint; sand bare timber until surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with at least two coats of semi-gloss or high gloss acrylic paint
  • where it is suspected that the building may be leaking and there is a risk of damage behind the cladding, engage an experienced building surveyor to report on the building
  • caution: old layers of paint may contain lead. Lead can be a health hazard if fumes, dust or paint fragments are swallowed or breathed in. For more information see Health and safety: lead-based paint

Cause

The back surface of boards is too close to the ground, not sealed and absorbing moisture

Repair

  • if any of the timber is rotted, cut it out and replace it with new treated timber. Aim for at least a 50 mm gap between the bottom of the cladding and the ground or paving to prevent moisture uptake
  • scrape and/or sand off loose paint; sand bare timber until surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with at least two coats of semi-gloss or high gloss acrylic paint
  • where it is suspected that the building may be leaking and there is a risk of damage behind the cladding, engage an experienced building surveyor to report on the building 
  • caution: old layers of paint may contain lead. Lead can be a health hazard if fumes, dust or paint fragments are swallowed or breathed in. For more information see Health and safety: lead-based paint

Cause

Concrete has been placed up to and against cladding

Repair

  • break up and remove concrete that sits against the cladding
  • if any of the timber is rotted, cut it out and replace it with new treated timber. Aim for at least a 50 mm gap between the bottom of the cladding and the ground or paving to prevent moisture uptake
  • scrape and/or sand off loose paint; sand bare timber until surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with at least two coats of semi-gloss or high gloss acrylic paint
  • where it is suspected that the building may be leaking and there is a risk of damage behind the cladding, engage an experienced building surveyor to report on the building 
  • caution: old layers of paint may contain lead. Lead can be a health hazard if fumes, dust or paint fragments are swallowed or breathed in. For more information see Health and safety: lead-based paint

Cause

There are high sub-floor moisture levels behind the cladding

Repair

  • if any of the timber is rotted, cut it out and replace it with new treated timber. Aim for at least a 50 mm gap between the bottom of the cladding and the ground or paving to prevent moisture uptake
  • scrape and/or sand off loose paint; sand bare timber until surface is sound; prime; fill joints with putty or exterior grade flexible (polyester) filler; paint with at least two coats of semi-gloss or high gloss acrylic paint
  • where it is suspected that the building may be leaking and there is a risk of damage behind the cladding, engage an experienced building surveyor to report on the building
  • caution: old layers of paint may contain lead. Lead can be a health hazard if fumes, dust or paint fragments are swallowed or breathed in. For more information see Health and safety: lead-based paint

Cause

The bottom of the cladding is too close to a waterproof deck surface, apron flashing and absorbing moisture  

Repair

  • if the construction is less than 10 years old, ask the original contractor back to look at the problem
  • if the original contractor is no longer around or the building was constructed over 10 years ago, engage an experienced building surveyor – a member of an industry body such as the New Zealand Institute of Building Surveyors. A surveyor can suggest possible repairs and can also assess the likelihood of damage behind the cladding if the problem has existed for a long time
  • for new construction, you can see the gaps required at the base of claddings in Acceptable Solution E2/AS1, for example, Figure 7 for apron flashings. With deck membranes and enclosed balustrades, a minimum gap of 35 mm between the bottom of the cladding and the deck membrane is shown in Figure 18
  • in most cases, repairs should be carried out by an experienced licensed building practitioner. A DIY solution should only be contemplated by someone with the knowledge, experience, skills and tools to do the job competently. Inappropriate or excessive removal of the bottom of the cladding may create further problems in the long run