Metal tile roofs – moss and lichen growth


Insufficient cleaning


  • follow the manufacturer’s recommendations for cleaning. More frequent washing is typically required in coastal or geothermal areas, or where there are industrial or agricultural chemicals in the air. If you plan to clean the roof yourself, always let someone else know when you are working at height. Make sure your access to the roof (ladder or scaffolding) is secure and on a stable base and wear shoes with a good grip

  • walk along lines supported by framing (which can usually be identified by lines of nails) or use a plank as a walkway to avoid damaging the tiles. Wash the roof with a soft-bristled brush and low-pressure hose

  • to deal with moss and lichen, proprietary chemical solutions can be applied with a garden sprayer. Different products act at different speeds. Do not expect all moss and lichen to be removed immediately – with some, the lichen can take several weeks to die and is gradually washed away over months of sun/rain weathering

  • at the same time as cleaning the roof cladding, check that roof penetrations and flashings remain weathertight and in good condition, and check and remove any debris from the guttering

  • if the tiles are in poor condition, considering recoating by a specialist company


The roof remains damp due to overhanging branches


  • wash the roof with water and a soft-bristled brush and remove any debris from the roof and gutters. Remove moss and lichen as described above

  • remove branches hanging over the roof. If you are doing this yourself, always let someone else know when you are working at height and ensure pets and children are out of the way. Make sure your access to the roof is stable and secure and your cutting tools are sharp. Wear shoes with a good grip and do not work on a wet or slippery roof. With large or heavy branches, remove in stages

  • for very large or tall trees, trees on steep ground or with branches close to power lines, consider using a professional arborist. Look for an appropriately trained/experienced practitioner, such as an approved contractor of the New Zealand Arboricultural Association