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Thatched Roof Maintenance | Cleaning Moss from a Thatched Roof

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  • Post published:January 17, 2019
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Thatched Roof Maintenance | Cleaning Moss from a Thatched Roof

The durability of a thatched roof largely depends on how well it’s cared for. Preventive maintenance extends the roof’s lifespan, while immediate repairs ensure slight damages don’t worsen to ruin the roof.

By employing a few inexpensive care practices, costly renovations can be avoided. Cleaning the roof every once in a while doesn’t cost much, yet it prevents damage that could result in the thatch requiring to be replaced. Corrective measures such as re-dressing the loosened thatch help prevents rainwater from seeping into the roof and causing the thatch to rot.

Storms, leaves, sticks, fir needles, birds and small animals can cause damage to a thatched roof. However, it’s moss, algae and fungi that pose the greatest threat. That’s why restricting their growth is taken to be the best way to help prolong the life of a thatched roof.

In recent years, moss and algae control has become a popular maintenance practice to prevent damage to these kinds of roofs. Methods to eliminate moss and algae have even been developed to ensure the roofs remain looking good, and remain watertight.

How to Care for and Maintain a Thatched Roof

Caring for a thatched roof primarily involves cleaning it to remove debris. It also entails re-tightening the loose thatch by a professional thatcher who understands how to do it correctly. These care activities are done at least once in every year and are better done by an expert. They help to prevent damage from extending deep into the thatch and shortening the roof’s life.

Debris on the surface of a thatched roof can cause damp conditions that promote the growth of fungi. Fungi is the thatched roofs’ enemy number one. It feeds on the cellulose in the thatch material, causing it to decompose. Unless the growth of the fungi is checked, it can mean having to replace the whole roof or part of it.

A thatched roof also requires what’s called brushing down. The care practice involves using special tools to remove moss found on the roof’s surface. Left to accumulate, moss and algae causes moisture to be retained for a long and encourages fungi to grow. The result is the rotting of the thatch and a roof whose lifespan is significantly reduced.

Re-attaching loosened thatch is another maintenance practice that contributes to the durability of a thatched roof. The process can even include replacing thatch blown off by severe winds. Re-tightening the wire that holds the thatch together is also done if it shows signs of loosening up. The activity requires an experienced Thatcher.

For a thatched roof to remain in top condition for years, the following maintenance measures are essential.

Frequent Cleaning

A thatched roof needs to be cleaned every once in a while. This serves to free it from debris and moss or algae that could cause it gradual and unnoticeable damage. The cleaning is done manually, with the help of a few tools and equipment. Using particular types of rakes, leaves, fir needles, and moss are pulled off the roof. The process exposes it to wind and sunshine, so moisture takes little time to leave the thatch. As a result, fungi don’t find a conducive environment to grow, which saves the thatch material from rotting.

Contrary to what some believe, brushing down moss from a thatched roof doesn’t cause damage to the thatch. Done by an expert, the cleaning only results in the damaged ends of the thatch stalks to falling off, leaving the excellent part intact.

The process doesn’t lead to the spread of fungi spores either. If anything, the presence of moss and algae on the roof promotes the spread of the spores by providing the right conditions for fungi growth. Besides, the thatching material is natural and bound to contain these spores. Danger only presents if the fungi spores provide the right environment to grow.

Controlling the Growth of Trees and Bushes

Excessive growth of trees and bushes around a thatched roof is not advisable. The shade cast on the roof by the trees or bushes prevents it from drying up quickly enough. With no sunshine and wind to evaporate water off the thatch, the roof would mostly remain damp, especially during days when the weather is rainy.

The leaves of trees also collect dew and drip dew onto the roof. It increases the moisture levels in the thatch, which can cause damage within no time. The dampness provides ideal living conditions for fungi growth. The result is a roof that starts to decompose slowly. By pruning trees that shade a thatched roof, moisture dries quickly enough to prevent fungi from finding favourable conditions to grow. The roof lasts longer, in addition to costing you fewer renovations.


Over time, thatch loses compactness and becomes exposed to the weather elements. Strong winds blow it about, and rainwater quickly finds its way into the layers. This can affect the roof’s durability if left unattended. Restoring the compactness involves using a Leggett to align the thatch material without affecting its arrangement. By re-dressing a thatched room when it shows signs of becoming loose, damage by wind, animals, rain and other elements can be avoided. It improves the roof’s lifespan and saves you the costs of carrying out heavy repairs over the years.

Controlling Moss and Algae Growth

As an expert in thatched roofs will tell you, moss and algae can cause thatching material to deteriorate rapidly. The two grow on the roof’s surface to create a thin film that covers the thatch and prevents it from drying properly. The roof stays moist for longer, allowing for fungi to thrive. The result is a roof whose lifespan is reduced. It’s the reason why controlling the moss and algae growth on thatched roofs is essential if you want it to last. Also, if you don’t want to spend huge amounts of money carrying out repairs on the roof as a result of damage by a fungus growth.

Ways to Control Moss and Algae on a Thatched Roof

It mainly involves the use of an algaecide. The chemical is applied using a spray gun but under low pressure. The chemical kills moss and algae when used correctly and at the right time. This, in turn, helps prevent the damp conditions caused by the film created by the growth of the two plants on the roof. As a result, fungi don’t grow on the roof. The thatch remains to look new for years, relieving you of the expenses of costly repairs. Controlling moss and algae growth on a thatched roof can add as many as 15 years to its lifespan by preventing the decomposition of thatching material. Using algaecides is also less costly than repairing damage caused by fungi.

What are Algaecides?

They’re the chemicals used to kill off algae or prevent growth. The popular ones are the quats or quaternary ammonium compounds. The chemicals are available in various forms. Quats don’t stick to the roof surfaces for long, so they must be applied regularly. Because they’re easily washed away by rain, algaecides are best applied during the dry season.

Application of Algaecides

There are various ways to apply algaecides. They include spraying, immersion, injecting, brushing and impregnation. Spraying a thatched roof with an algaecide is better done during days when conditions are dry. Also, when temperatures are not too low. The growth of moss and algae is highest when the weather is warm. Much of the control agent will, therefore, be absorbed. As a result, the algaecide would stand a good chance of killing off the plants.

It’s advisable to keep the roof sprayed with an algaecide moist for at least half an hour. This is especially essential during the summer when moisture dries off a surface much more quickly. Moss and algae require this length of time to absorb the chemical fully. If the thatch happens to dry earlier than this, it can mean reduced effectiveness of the algaecide.  The chemical must be sprayed in the right amounts for it to work. Estimating the cost of spraying a particular area of thatch may not be possible as the chemical prices vary from manufacturer to manufacturer.

Effects of Algaecides

Quaternary chemicals are not as strong as those containing Diuron. They act by perforating the cell membranes of fungi, algae and moss, causing the plants to die. For that to occur, the plants must absorb adequate amounts of the chemical. The person spraying the control agent must ensure that by following the correct application procedure and chemical amounts. The method of application, therefore, matters a lot. Care should be taken such as ensuring enough algaecide is sprayed on the roof’s surface. The thatch should also be adequately moistened to allow maximum chemical absorption.

There are times when the algaecide doesn’t work as expected. If that happens, the problem will likely be with how the spraying was done. It can also be that too little of the chemical was applied, or it could be that the moisture was too much and ended up diluting the chemical’s potency. In such cases, it would be necessary to repeat the process and follow the proper application procedures.

Quats-based biocides don’t present many environmental risks or roof risks. They are almost harmless to vegetation and will not affect the gardens around the house whose roof is being treated. However, ponds that are too close to the house would need to be covered. Quats are not safe for fish and could result in adverse effects. During application, sprayers should be thoroughly washed and rinsed.

Effects of Algaecides on Humans

The chemical can be dangerous when in a mist or foam state. It’s advisable to avoid inhaling it in a closed room as it can lead to severe complications. The chemical can irritate the skin and the mucous membrane in low concentrations. Symptoms include a dry throat, coughing and, in some cases, nausea. Wearing protective clothing when applying an algaecide can significantly limit exposure and prevent these poisoning symptoms. Following the correct application procedures, such as the right dosing, also helps to ensure safety.

To Sum Thatched Roof Maintenance | Cleaning Moss from a Thatched Roof

A thatched roof can last if cared for. That involves cleaning out, red-dressing it and other maintenance practices. It also involves the use of algaecides to control moss and algae growth. Despite the products mentioned here being in use, the length of time the chemical remains active to control moss and algae is not known. What’s known, though, is that algaecides are easily washed away by rain and don’t stay on the roof for long enough. If applied during the wet season, it means they’re less effective.

The chemical only kills the moss or algae growing at the time of application and will not prevent future growth. Monitoring the roof is the best indication of when to reapply the algicide. The environment surrounding the thatch will determine best the rate at which the moss returns.


Maintaining a thatched roof is a complex and delicate task and one best left to the experts. Professional thatched roof maintenance from our team of experienced technicians ensures cleaner roofs for longer, with thorough moss removal for better air circulation, improved efficiency and enhanced aesthetic appeal. Our specialized cleaning techniques are tailored to each roof type, ensuring optimal results without damaging your existing structure.If you require free advice on  Thatched Roof Maintenance | Cleaning Moss from a Thatched Roof, please call us on 08000933267 or email us HERE