Thatched Roof Maintenance Explained - Brushing a Thatch Roof

It is an inescapable fact that all thatch roofs have a lifespan but there are ways to prolong the natural life of any thatch roof. Caring for a thatched roof can be high maintenance - especially if small contributors to degradation of the roof have not been managed properly over time. Many more serious problems can be prevented through consistent maintenance and assessment of the state of the roof.

"Brushing" is a term often used in the thatching industry to describe one of these maintenance tasks. If you are unfamiliar with the term then read on - this blog explains what the term brushing means, why all thatch roofs should be brushed and various methods that are used by contractors to brush thatched roofs.


What is Brushing?
Brushing (or combing) when used in the context of thatching, is the process of removing the top-most layer of thatch from the entire area of a roof. The ends of the thatch, the outer layer of the roof, slowly rot as they are exposed to the elements. This thin layer of rotten thatch is removed during brushing.

Rotten layer of thatch roof desperately in need of brushing

Thatch roof after brushing (top) and before brushing (bottom)

 Why does a Thatch Roof need to be Brushed?
It is highly important to brush a thatch roof several times during it's lifespan, to prolong the life of the roof. The thin, rotten, outer layer of thatch holds moisture.This moisture, if left to age will gradually penetrate deeper and deeper into the roof and increase the amount of moisture in the thatch. As a result of this moisture held in the roof, the thatch will eventually turn to compost. Brushing removes this outer layer allowing the deeper thatch to dry out, once this outer thatch has reached an age, it will be removed. This cycle continues throughout the life of a thatched roof. Because if this cycle it is important not to remove too much thatch when brushing as this will make the thatch thinner more quickly and shorten the lifespan of the roof. Generally a roof should have 3-4 brushings "in it" i.e., it should be thick enough to allow 3-4 separate occasions of brushing over the years before it needs to be re-thatched.

When should a thatch roof be brushed?
As a general guide most thatched roofs need brushing ever 8 or so years. However, it depends highly on the choice of thatch, the pitch of the roof, the local climate and the quality of the thatch. Some roofs can go for 15 years+ without being brushed, others will need brushing after only 4 years. It is important to speak to an thatching specialist who can give you an accurate assessment of the state of the thatch and the roof as a whole, before work is undertaken.

How do contractors brush thatch roofs?
There are several methods of brushing thatch roofs, the choice of method often depends on the type of thatch and the contractor themselves.
It is possible to brush a roof by hand or with pruning sheers. The method in this case is to pull out sections of the thatch, cutting or breaking off the rotten ends and then pushing or brushing the thatch back into place on the roof and compacting it. This method is obviously slow and is an out-dated method generally used by very small-scale contractors.
We have found that the most effective and efficient way to brush a roof is to use a hedge cutting machine which can cut off the outer layer of thatch without sections having to be pulled out of the roof - this means much less disturbance of the roof itself. The thatch is still then brushed and pushed into place to compact the thatch.

Thatchers brushing roof with machine

Thatch roof in the process of being brushed

Roof Compaction & Finishing the Job
The compaction of a thatch roof is one of the most important contributing factors to prolonging the roofs lifespan. If the thatch is loose and not tightly packed it encourages moisture to be retained more deeply in the roof as well as increasing the probability of weather damage, and making animal and bird damage much more easy. The thatch must form a solid roof to be effective.
It is important that whichever method is used to brush the roof, the roof is compacted afterwards. This is done by pulling and tensioning the twines from the inside of the roof. In some cases this is not possible - unfortunately many contractors use twines with a shorter lifespan than the thatch itself and when they are pulled to re-tension, they break. It is important to check what type of fasteners/ twines a contractor is using.
If the roof has poor compaction and has been brushed, it is possible to add bundles of thatch as the roof is being brushed to achieve a higher density of thatch on the roof.

Thatch roof before brushing and repairs

Thatch roof after brushing & fitting valley section

For more information on other types of maintenance required on thatch roofs visit our website.

Cintsa Thatching offers a long-term maintenance package which covers an assessment of the roof and long term maintenance plan performed by our highly experienced thatchers.