Asbestos roofing – moss or lichen

Cause

Insufficient cleaning

Repair

  • 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 roof 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. Keep the roof wet while brushing and collect all the waste into plastic bags – you will need to disconnect downipes and catch the debris in a muslin bag or similar. When working on the roof:

    • work only in calm conditions

    • lay protective boards across the surface to walk on

    • wear a disposable P2 mask and disposable overalls and gloves

    • do not do anything that would lead to asbestos fibres becoming airborne

  • label the sealed bags “Asbestos hazard” and disposed of at places approved by the local authority for asbestos disposal

  • do not use a water blaster on the roofing

  • a clean and sound roofing surface may be ‘encapsulated’ by painting or repainting with 2 coats of high-build acrylic elastomeric coating

  • where the asbestos fibre-cement roofing is in poor condition or sheets are cracked it will need to be removed by a licensed asbestos removalist and a new roof 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 very strictly controlled. You can find more asbestos details for homeowners on the WorkSafe website.

Cause

The roof remains damp due to overhanging branches

Repair

  • cut back the overhanging branches hard so the roof can dry 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 roof 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. Keep the roof wet while brushing and collect all the waste into plastic bags – you will need to disconnect downipes and catch the debris in a muslin bag or similar. When working on the roof:

    • work only in calm conditions

    • lay protective boards across the surface to walk on

    • wear a disposable P2 mask and disposable overalls and gloves

    • do not do anything that would lead to asbestos fibres becoming airborne

  • label the sealed bags “Asbestos hazard” and disposed of at places approved by the local authority for asbestos disposal

  • do not use a water blaster on the roofing

  • a clean and sound roofing surface may be ‘encapsulated’ by painting or repainting with 2 coats of high-build acrylic elastomeric coating

  • where the asbestos fibre-cement roofing is in poor condition or sheets are cracked it will need to be removed by a licensed asbestos removalist and a new roof 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 very strictly controlled. You can find more asbestos details for homeowners on the WorkSafe website.