Plywood cladding – paint failure at base of walls

Cause

Cladding covered by soil/foliage

Repair

  • cut back foliage and replace any plants that are likely to regrow and cause the problem to return

  • lower the soil level to be well clear of the cladding – the bottom of the plywood must be able to dry completely

  • check for damage to the plywood. Where plywood is damaged, replace it with H3 LOSP-treated ply with a 3-coat paint finish or H3 CCA-treated material, ensuring the base of the new cladding is a minimum 35 mm clear of the ground

  • where framing behind the cladding is damaged (unless it is limited to a small area of timber), engage a registered building surveyor to advise on the cause, extent and repair options

  • where the plywood is sound, allow it to dry out completely. Scrape off loose paint and sand until the surface is sound. Seal the plywood – especially the edges – and repaint.

Cause

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

Repair

  • lower the soil level to be well clear of the cladding – the bottom of the cladding must be able to dry completely

  • check for damage to the plywood. Where plywood is damaged, replace it with H3 LOSP-treated ply with a 3-coat paint finish or H3 CCA-treated material , ensuring the base of the new cladding is at least 35 mm clear of the ground

  • where framing behind the cladding is damaged (unless it is limited to a small area of timber), engage a registered building surveyor to advise on the cause, extent and repair options

  • where the plywood is sound, allow it to dry out completely. Scrape off loose paint and sand until the surface is sound. Seal the plywood – especially the edges – and repaint.

Cause

Concrete has been placed up to and against cladding

Repair

  • break up and remove concrete or paving. Reform the ground surface so rainwater will flow away from the building

  • check for damage to the plywood. Where plywood is damaged, replace it with H3 LOSP-treated ply with a 3-coat paint finish or H3 CCA-treated material, ensuring the base of the new cladding is well clear of the ground

  • where framing behind the cladding is damaged (unless it is limited to a small area of timber), engage a registered building surveyor to advise on the cause, extent and repair options

  • where the plywood is sound, allow it to dry out completely. Scrape off loose paint and sand until the surface is sound. Seal the plywood – especially the edges – and repaint.

Cause

High subfloor moisture levels behind the cladding

Repair

  • reduce subfloor moisture levels:

    • if there is a leak under the house, identify the source and location. Make a permanent repair, or call a licensed or certifying plumber (work on waste pipes must by law be carried out by a licensed or certifying plumber)

    • if surface water is running under the house, divert it away by lowering the ground levels around the building and sloping the ground away from the house

    • clear away obstructions around the house perimeter such as planting or soil build-up outside the vents

    • for painted vents or grilles, remove paint build-up that may reduce the air path space

    • clear away items stored under the house to improve air flow

    • ensure there is not less than 3500 mm² of clear open subfloor venting (grilles or gaps between baseboards) for every 1 m² of floor area

    • make ventilation openings high in the subfloor space, near to the underside of bearers

    • spread vents evenly around the building perimeter to allow cross-ventilation.

  • check for damage to the plywood. Where plywood is damaged, replace it with H3 LOSP-treated ply with a 3-coat paint finish or H3 CCA-treated material, ensuring the base of the new cladding is well clear of the ground

  • where framing behind the cladding is damaged (unless it is limited to a small area of timber), engage a registered building surveyor to advise on the cause, extent and repair options

  • where the plywood is sound, allow it to dry out completely. Scrape off loose paint and sand until the surface is sound. Seal the plywood – especially the edges – and repaint.

Cause

Bottom of cladding too close to waterproof deck surface, apron flashing and absorbing moisture 

Repair

  • check for damage to the plywood. Where plywood is damaged, replace it with H3 LOSP-treated ply with a 3-coat paint finish or H3 CCA-treated material, ensuring the base of the new cladding is well clear of the ground

  • where framing behind the cladding is damaged (unless it is limited to a small area of timber), engage a registered building surveyor to advise on the cause, extent and repair options

  • where the plywood is sound, allow it to dry out completely. Scrape off loose paint and sand until the surface is sound. Seal the plywood – especially the edges – and repaint.