Rot at base of stained or clear-finished timber weatherboard walls

Causes

Boards covered by soil or foliage

Boards have had concrete poured against them or are touching the ground

Boards not painted along the bottom edge 

Listed under: Exterior, finishes, clear finishes, timber and wood-based, stain, timber, cladding, walls, moisture, durability, rot, leaks, wall cladding, stained or clear-finished timber weatherboards

Cause

Boards covered by soil or foliage

Repair

  • remove soil/foliage covering weatherboards
  • replace rotten weatherboards with minimum H3.2-treated weatherboards. Ensure there is at least at least a 50 mm gap (preferably more) between the bottom of the cladding and the ground. This is less than the gap required in new construction (which for weatherboard walls is 100 mm above a paved surface or 175 mm above a finished unpaved surface) but could reduce the risk of moisture uptake and allow the boards to dry. The new construction requirements of a 100 mm/175 mm gap should be used if possible
  • remove rotten section(s) of weatherboard(s) as follows:
    • splay (slant) cut back to nearest studs (at least 600 mm in both directions)
    • treat cut ends of existing boards with paint-on preservative
    • prime cut ends of timber
    • insert new boards,
    • ensure that back face and ends of timber are primed
    • nail edges of existing and new boards to studs using one nail per stud and board
    • prime
    • fill joints with putty or exterior grade flexible (polyester) filler
    • paint with minimum two coats of semi-gloss or high gloss acrylic paint
  • before replacing boards, check that the wall underlay (building paper) and framing behind weatherboards are sound
  • if a weatherboard is badly affected by rot it may be easier to replace the entire board rather than trying to partially replace board
  • 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

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Cause

Boards have had concrete poured against them or are touching the ground

Repair

  • break up and remove concrete
  • replace rotten weatherboards with minimum H3.2-treated weatherboards. Ensure there is at least at least a 50 mm gap (preferably more) between the bottom of the cladding and the ground. This is less than the gap required in new construction (which for weatherboard walls is 100 mm above a paved surface or 175 mm above a finished unpaved surface) but could reduce the risk of moisture uptake and allow the boards to dry. The new construction requirements of a 100 mm/175 mm gap should be used if possible
  • remove rotten section(s) of weatherboard(s) as follows:
    • splay (slant) cut back to nearest studs (at least 600 mm in both directions)
    • treat cut ends of existing boards with paint-on preservative
    • prime cut ends of timber
    • insert new boards,
    • ensure that back face and ends of timber are primed
    • nail edges of existing and new boards to studs using one nail per stud and board
    • prime
    • fill joints with putty or exterior grade flexible (polyester) filler
    • paint with minimum two coats of semi-gloss or high gloss acrylic paint
  • before replacing boards, check that the wall underlay (building paper) and framing behind weatherboards are sound
  • if a weatherboard is badly affected by rot it may be easier to replace the entire board rather than trying to partially replace board
  • 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

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Cause

Boards not painted along the bottom edge 

Repair

  • break up and remove concrete
  • replace rotten weatherboards with minimum H3.2-treated weatherboards. Ensure there is at least at least a 50 mm gap (preferably more) between the bottom of the cladding and the ground. This is less than the gap required in new construction (which for weatherboard walls is 100 mm above a paved surface or 175 mm above a finished unpaved surface) but could reduce the risk of moisture uptake and allow the boards to dry. The new construction requirements of a 100 mm/175 mm gap should be used if possible
  • remove rotten section(s) of weatherboard(s) as follows:
    • splay (slant) cut back to nearest studs (at least 600 mm in both directions)
    • treat cut ends of existing boards with paint-on preservative
    • prime cut ends of timber
    • insert new boards,
    • ensure that back face and ends of timber are primed
    • nail edges of existing and new boards to studs using one nail per stud and board
    • prime
    • fill joints with putty or exterior grade flexible (polyester) filler
    • paint with minimum two coats of semi-gloss or high gloss acrylic paint
  • before replacing boards, check that the wall underlay (building paper) and framing behind weatherboards are sound
  • if a weatherboard is badly affected by rot it may be easier to replace the entire board rather than trying to partially replace board
  • 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

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