How do I remove moss or lichen from my roof?
Low to moderate moss or lichen growth on a roof is a natural part of the ageing process on many pitched roofs. Under normal circumstances this is not harmful to roof tiles or slates, so unless the roof is leaking or the gutters/outlets are blocked, then the best advice is to leave the moss/lichen where it is and not to access the roof to remove it.
This is because the removal of moss and lichen can cause further damage to the tiles and the roof in general, either from foot traffic on the tiles/slates or from some of the methods often used. However, heavier build-ups of moss and lichen can significantly detract from your home's appearance and potentially cause damage over time if left unchecked.
Let’s look at the reasons why these growths can appear on the roof, how to prevent them and what to do if you do need to remove lichen or moss from roof tiles.
When do I need to remove lichen or moss from roof tiles?
Moss and lichen tend to flourish on roofs in rural areas, where trees are nearby and where there are shady, damp conditions.
Steeper pitched roofs are less likely to support moss and lichen growth as they shed water more quickly than roofs with a low pitch. In contrast, shallow roofs tend to remain damper for longer and therefore may attract moss and lichen more readily. In addition, moss and lichen is more likely to grow on a North facing elevation as it is in shade more than other aspects of the roof.
A heavy build-up of moss and lichen will inhibit the flow of water off the tiles, so the roof covering stays wetter for longer, this increases the chance of roof leaks and can also accelerate the deterioration of the roof tiles. In these cases, the removal of moss and lichen should be considered, and in extreme circumstances, it may be necessary to replace some or all of the tiles in the affected areas, rather than clean them.
Do moss and lichen need to be removed from roof-mounted solar panels?
Moss or lichen are unlikely to grow on the solar panels themselves but can appear around and under them – particularly on the underside of on-roof solar panels in the shady space between the panels and the roof. The shade, combined with trapped moisture and debris that can accumulate under on-roof PV panels, provides an ideal environment for these growths to develop.
Opting for roof-integrated solar panels can help homeowners prevent the growth of moss or lichen on a roof. Because roof-integrated solar, such as the Marley Solar Tile, sits flush with the roof surface, there are no shaded areas underneath where moss and lichen can accumulate. This helps maintain the roof’s appearance and the efficiency of the solar system.
Methods for removing moss or lichen from roof tiles
There are several methods available for removing moss and lichen from your roof. The best method for you will depend on the extent of the growth and the condition of your tiles.
Spraying moss with a toxic wash – A toxic wash solution can be used to wash the roof, although care must be taken as the solution can be harmful to plants and animals. It is also careful to ensure gutters and outlets are protected during this process.
Scraping moss off the roof – Moss can be scraped off with hand tools, but this must be performed with caution to avoid damaging roof tiles and slates.
Please note that, while pressure washing might seem like a good choice for removing moss or lichen from a roof, it can cause a lot of problems and is not recommended by most roofing professionals. High-pressure washing can damage roof tiles, particularly older or more delicate ones and flood the roof and outlets with unwanted water, chemicals, and debris. If done from ground level, the upward movement of the spray can also lift and damage the tiles.
Accessing the roof to remove moss or lichen yourself should not be attempted due to the inherent risks of working on roofs and can result in accidental damage or injury, so it's best to leave this job to experts who can ensure the roof is cleaned effectively and safely. A competent roofing operative will have the skills and tools necessary to navigate the roof safely, remove moss and lichen and ensure any necessary remedial works are also carried out.
Preventing the growth of lichen and mould on roofs
Taking steps to prevent moss or lichen growth on roof tiles in the first place can help avoid the need for removal down the line.
Consider installing zinc or copper strips at high level (normally to the ridge and hip tiles) to inhibit moss growth on the roof. Zinc or copper ridge and hip cappings can also be fitted across the roof ridge and hip lines. When it rains, small amounts of metal are released onto the roof surface, creating an environment that inhibits the growth of moss and lichen.
Regular roof maintenance is crucial to prolonging a roof's lifespan and preserving its integrity. This should include inspecting for broken and loose tiles, checking gutters and downpipes, and removing any organic material that may have built up, such as leaves, moss and lichen. Trim back overhanging branches to reduce shade, and periodically inspect your roof for any signs of moss or lichen starting to form.
Questions about removing moss or lichen from a roof? Ask Marley
Removing moss and lichen can be an important part of maintaining clay and concrete roof tiles, as well as the aesthetics and overall performance of your roof.
By assessing the roof’s condition, choosing the right removal method and taking steps to prevent future growth, you can protect your roof and keep it looking its best.
Before proceeding with any remedial work to remove moss or lichen, we recommend speaking to a roofing maintenance professional. If unsure, contact the Marley technical department for further advice.