The correct maintenance will extend the lifetime of a thatched roof. This will involve small repairs to the thatch, cleaning, re-dressing loosened thatch and applying treatments to prevent the ingress of rainwater and causing the thatch to rot. Damage can be caused by leaves, fir needles, birds, storms and small animals but moss, algae and fungi penetration are the worst offenders.

Regular Attention

A roof will benefit from cleaning away debris, re-tightening loose thatch and brushing down, all of which your professional thatcher will carry out.

Each of these activities will prevent damage from extending deep into the thatch and shortening the roof life. Debris can cause damp conditions that promote the growth of fungi. Fungi feed on the cellulose in the thatched material causing it to decompose. Unless the growth is checked it can mean having to replace the whole or part of it.

Brushing down involves the use of special tools to remove moss that’s found on the roof’s surface. Left to accumulate, moss and algae causes moisture to be retained for longer and encourages fungi to grow. The result is rotting of the thatch and a roof which lifespan is greatly reduced.

At the same time the thatcher will re-attach loosened thatch which is also another maintenance practice that contributes to the durability of the roof. The process can even include replacing thatch that’s been blown off by severe winds. Re-tightening the wire that holds the thatch together is also done if it shows signs of loosening up.

For a thatched roof to remain in good condition for years it is best that the following measures are carried out.


Cleaning helps to free thatch from moss, algae or debris that could cause it damage unseen over time. Manual cleaning will ensure that moss, fir needles and leaves are removed from the roof. Moisture can build up over time causing it to remain wet even in dry conditions and as result it can allow fungi to take hold. Cleaning saves the thatch material from rotting.

Brushing Down

Brushing down moss from a thatched roof doesn’t cause damage to the thatch provided an expert carries it out. It only results in the damaged ends of the thatch stalks to fall off leaving the unaffected part intact. It will not lead to the spread of fungi spores either. The presence of moss and algae on the roof promotes the spread of the spores by providing the right conditions for fungi growth.

Trees and Bushes

The growth of trees and bushes around a thatched roof is best avoided as the shade cast on the roof by the trees or bushes prevents it from drying out quickly. Sunshine and wind help to evaporate water off the thatch.  Tree growth encourages wetness allowing dew to drip onto the roof from its leaves, which can cause damage within no time. This dampness provides ideal living conditions for fungi growth resulting in the slow decomposition of a roof. It is best to keep overhanging trees regularly pruned to prevent fungi from finding favourable conditions to grow.

Moss and Algae Control

Moss and algae can cause thatching material to deteriorate rapidly by creating a thin film that covers the thatch and prevents it from drying properly. The roof stays moist for longer allowing fungi to thrive so reducing the lifespan of a thatched roof. The control of moss and algae growth on thatched roofs is essential if you want improve its life.

It is controlled by the use of a biocide chemical. BioClear Pro is recommended for use on thatch. The use at the right time and under the correct conditions will cause the chemical treatment to kill moss and algae. This will result in the thatch looking newer for years, relieving you of the expense of costly repairs. In many cases the lifespan of the roof can be extended long as 15 years by preventing the decomposition of thatching material. Using biocides is also less costly compared to having to repair damage caused by fungi.


The thatch on a roof loses compactness and becomes exposed to the weather elements over time. Also the effect of winds blow it about and rainwater finds its way into the layers. Your thatcher will use a tool called a Leggett to tighten the thatch showing a lack of compactness to align the thatch material when it shows signs of becoming loose. This improves the roof’s lifespan and saves you the costs of carrying out heavy repairs to over the years.

BioClear Pro and it’s Application

Biocides are the chemicals we use to kill off algae or prevent growth. Care needs to be taken in their application as some do not stick to the roofs surfaces for long which means they need to be applied regularly and are best applied during the dry season.

Biocides can be applied in various ways including injecting, spraying, immersion, brushing and impregnation. Spraying is the normal means and treating a thatched roof with BioClear Pro and it is better done during days when conditions are dry and when temperatures are not too low. The growth of moss and algae is highest during times when the weather is warm.

Moss and algae need at least half and hour of moisture treatment to the roof during the spraying process, especially essential during the summer when moisture dries off a surface much more quickly. Also this length of time will allow the thatch to fully absorb the chemical. If the thatch happens to dry earlier than this it can mean reduced effectiveness.

In Conclusion

The lifetime of a thatched roof can be increased if cared for by cleaning out, re-dressing and other maintenance, including the use of biocides to control algae growth. It is beneficial to consider regular biocide treatments as the chemical only kills the algae etc that’s growing at the time of application, and will not prevent future growth.

Keep a regular eye on the condition of your thatch and contact a professional thatcher where damage is detected or if you need advice on thatched roof maintenance. Where moss or fungi are a problem please do not hesitate to call or email ourselves at Greenway Softwashing.

Soft washing is a safe and very effective low pressure cleaning and sanitizing method, for both domestic and commercial properties.


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Corse Lawn
GL19 4LZ
United Kingdom

01452 780780


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