Thatched Roof Lifespan – How Long Do Thatch Roofs Last?
A thatched roof adds a certain amount of character to a building that you just can't get from roofing tiles or metal products. Here in the UK, we tend to be very fond of thatched roofs due to their historical significance. Thatched roofs have been part of the British landscape for hundreds of years – perhaps as far back as the eighth century AD. But rest assured that the average thatched roof lifespan isn't that long.
Under normal conditions, a good thatched roof will not last more than 60 years without requiring major repairs. At the hands of a skilled craftsman, though, it is possible to preserve the first layer of a thatched roof by applying a new coat over the top of it, thus making it feasible to save the original roof for hundreds of years. In fact, there are plenty of examples across the UK of this very thing. But by and large, 60 years is about the best you can do.
What determines thatched roof lifespan? An extensive list of factors we will discuss in this article. We will begin with the materials used – both on the original roof and any additional coats added over the years.
Life Expectancy of Materials
A thatched roof is, by nature, an organic roof. That means the materials used to construct it will break down over time. Hundreds of years ago, property owners could have used dozens of different materials to create their thatched roofs. Everything from wild grasses to wetland plants was utilised. Today, the three most commonly used materials are water reed, combed wheat reed, and long straw.
Water reed is imported more often than not due to British agricultural practices that tend to be damaging to domestic product. At any rate, the average water reed roof lasts between 35 and 40 years. A specific kind of water reed, known as Norfolk reed, can last as long as 60 years if the material is in excellent condition at installation.
Combed wheat reed is a form of long straw that is processed in a very specific way to produce a unique look and texture. It is the most commonly used material in Devon, as well as several other English counties. Combed wheat reed lasts 25 to 35 years on average.
Last is long straw. This material is typically used for agricultural buildings and less expensive homes. It is an all-purpose thatched roof material that can be used to complete nearly any design. Its lifespan is typically 20 to 25 years.
As you can see, different kinds of materials have longer life expectancies than others. One thing to note is that a roof ridge typically lasts no longer than 15 years regardless of the material used to construct it. Why? Because the ridge is the weakest link in roof construction. The ridge takes most of the punishment from weather, animals, debris, and so forth. Property owners should expect to replace a roof ridge at least once or twice during their lifetimes.
Factors that Affect Thatched Roof Lifespan
The lifespans listed above are just averages. Obviously, there are a tremendous number of factors that directly affect the lifespan of any roof, whether thatched or not. Of course, there are factors that are more important to thatched roofs than those made of slate or other materials.
Here is a list of the top 10 factors known to affect the lifespan of thatched roofs:
- As previously explained, different thatching materials have different lifespans. But even within these various materials there are differences. For example, imported water reed is preferred because it is not subject to the same kinds of agricultural conditions domestic product is exposed to. Therefore, it's generally accepted that imported water reed lasts longer than domestic water reed – except for Norfolk reed, of course.
2. Quality of Roofing Materials - Second only to the materials themselves is the quality of those materials at the time of installation. This is important because thatch goes through a rather rigorous process before it is suitable as a roofing material. Plant material is cut, bound, ripened, threshed and then bundled for sale. How this process is completed partly determines the quality of the material at the time of installation.
Age and storage are additional factors that can impact quality. Thatch that has not been stored improperly can absorb excessive moisture that promotes mould growth. Thatch that has been stored for too long can become brittle if not protected from the elements. The goal is to make sure the thatcher is using materials of the highest possible quality.
3. Roof Pitch - Believe it or not, roof pitch plays a significant role in determining thatched roof lifespan. Roof pitch is critical to moisture run-off, so a roof with an inadequate pitch could retain more moisture and thus experience a shorter lifespan. On the other hand, a roof with a high pitch could be exposed to more wind damage in some climates. Wind definitely affects lifespan – which leads to the next point.
4. Normal Weather Conditions - The biggest enemy of a thatched roof is weather. From moisture to wind to sunlight, the elements take their toll on thatched roofs like nothing else. That means the weather in the local area will affect the lifespan of your thatched roof. The most important thing to worry about is moisture.
As thatch is organic, it is prone to breakdown when moisture is present. That's why thatched roofs in a very humid environment don't last as long as comparable roofs in drier environments. The same goes for locales that see a lot of rain. Property owners should expect a shorter lifespan in areas where moisture and wind are above average.
5. Surrounding Landscape - People are surprised to learn that the surrounding landscape can affect the life of a thatched roof. For example, consider a house surrounded by trees. If those trees are dense enough to block out sunlight and prevent the free movement of air, moisture could build up in a thatched roof and thus reduce its lifespan. This is why master thatchers recommend keeping the area around a thatched roof house clear of trees and other obstacles that could cause problems.
6. Environmental Pollutants - Environmental pollutants are also known to reduce thatched roof lifespan. Just like organic materials break down with exposure to moisture, they can also be encouraged to decay due to exposure to certain chemicals. As a general rule, thatched roofs located near metropolitan areas tend to have shorter lifespans than those in rural areas.
7. Birds and Rodents - As you might expect, birds and rodents are fond of thatched roofs. The natural materials used to make thatch also make welcoming homes for these pests. Thatched roof lifespan will, therefore, be reduced if pest infestation is a continual problem. Thatchers recommend installing plastic netting on roofs that are prone to bird and rodent problems.
8. Roof Breathability - Thatched roofs tend to breathe very well on their own. Rarely is attic venting needed in a structure with a thatched roof because the natural materials breathe so well. But in cases where poor design or installation results in poor breathability, the lifespan of a thatched roof will be reduced. It goes right back to the moisture problem. A roof that cannot breathe is prone to decay due to trapped moisture.
9. Human Damage - The most important rule for extending the lifespan of a thatched roof is to ensure that the roofing materials remain undisturbed for as long as possible. This suggests that allowing tradesman to walk across the roof is not a good idea. People unfamiliar with thatch and its properties can unknowingly do damage simply by going about their business doing things like repairing chimneys, replacing flashing, mounting antennas, trimming trees, etc.
10. Quality of Craftsmanship - Last but not least is the quality of craftsmanship in the original roof. A master thatcher with years of experience should be able to install a thatched roof that offers a maximum lifespan based on the materials chosen. A contractor not considered a master of the trade may not be able to produce the same level of quality. In short, the skill of the thatcher significantly influences thatched roof lifespan.
Now you know the top 10 influences affecting the lifespan of a thatched roof. Suffice to say that a thatched roof installed by a master craftsman using high-quality materials should provide decades of reliable service. Paying to install a high-quality roof should, in most cases, mean that the roof will outlive the person who installed it. That's a good thing. And it is one of the many advantages of choosing a thatched roof over another alternative.