Once the moss has been removed from the roof, we recommend the tiles be drenched with a suitable chemical to treat any remaining moss spores that may be hidden under the tile laps or joints.

If the roof isn’t treated, the moss will start to grow back as soon as it rains although the amounts will be small at first and may not be noticeable until about a year later.

If the moss is removed and the tiles treated, this is roughly how long it takes:

Roofs that were heavily infested and receive very little direct sunlight and are almost always in the shade from overhanging trees etc: 12-18 months.

Typical roofs that had normal amounts of roof moss: 18-24 months.

Roofs that had little moss growth and are bathed in sunlight, no overhanging tree branches and south facing etc: 24-36 months.

As a general guide, we recommend re-treating the roof with the chemical every 18 months to prevent the moss, algae or lichen from taking hold again. It’s far cheaper to re-spray the roof every 18 months than to pay for manual moss removal again.

If the roof was heavily infested, we suggest a respray every 12 months.

See how we remove and prevent roof moss.

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