Moss or lichen on asbestos-cement cladding

Cause

Insufficient cleaning

Repair

  • cement-based wall cladding installed up to the late 1980s may contain asbestos, especially cladding with a corrugated profile or shiplap or board and batten sheets. A dimpled back surface may also indicate asbestos, but identifying this may only be possible where it is installed on a shed or garage without wall underlay, or where a piece has fractured and dropped out

  • if you are not sure whether a fibre-cement cladding contains asbestos, you can get a small piece (about the size of two $2 coins, or approximately 2 x 3 cm) tested at one of the labs listed on our asbestos page

  • if the wall cladding is in good condition, apply a proprietary surface biocide with low pressure. Leave until the moss or lichen is dead then remove as directed by the biocide manufacturer. Some manufacturers recommend waiting for dead moss/lichen to fall off as the surface weathers. When working on the cladding:

    • work only in calm conditions
    • wear a disposable P2 mask and disposable overalls and gloves
    • do not do anything that would lead to asbestos fibres becoming airborne
  • do not use a water blaster on the cladding

  • keep the waterproof or paint coating on any fibre-cement cladding in good condition

  • where asbestos fibre-cement is in poor condition, fibres are being shed or sheets are cracked, it will need to be removed by a licensed asbestos removalist and a new cladding installed. You can find a registry of licensed removalists on the WorkSafe New Zealand website.

Breathing in asbestos fibres can lead to serious and potentially fatal illnesses. Work with materials that contain asbestos is strictly controlled. You can find more asbestos details for homeowners on the WorkSafe website.

Cause

Walls and eaves continuously damp due to heavy planting/overhanging trees/a bank in close proximity

Repair

  • cut back planting or overhanging trees. Where possible, redesign the garden/planting to prevent the problem recurring

  • as for the first repair above

Cause

South walls not exposed to sunlight

Repair

  • as for the first repair above

Cause

Continuous wetting from overflowing gutter or pipe

Repair

  • repair the guttering or pipe

  • as for the first repair above