|Rethatching - Before and After|
Even though water reed lasts 40 to 50 years, the time for rethatching will come around once every lifetime. (And if it comes around twice, thank your lucky stars!) The Thatch Company team has rethatched many an old building.
Here's what Robert West, author of Thatch, a manual for owners, surveyors, architects and builders has to say about the causes of deterioration. "In general terms, the largest single reason for thatch to deteriorate is directly related to the length of time that moisture is retained on the surface of the coat. Microbiological activity takes place in wet warm conditions, causing the reed or straw to break down. Thus the drier the climate, the more exposed the roof and the steeper its pitch, the longer the material will last.
Any part of the thatch protected from surface water will show litte or no sign of deterioration over an extended period. It is fair to say that frequently one finds the original straw base coat still in perfect condition in the roof space of centuries-old cottages."
The first part of a rethatching project is to strip the old and damaged thatch from the roof. Waterproof tarpaulins are put in place over the roof to protect the building from any rain damage during this phase. These covers are then rolled back out of the way during the working day. Keeping this in mind, you'll want to schedule your rethatching job well in advance so that the winter rainy season is avoided.
If the underlying layers of thatch are still good, these are retained and covered by newer reeds. The task of marrying the new and the old thatch is particularly tricky at corners, so be sure to hire people who know what they're doing for such a task. In this picture, you can see the old thatch on the left side of the house. The new bundles of reed are stacked around the scaffolding ready for use.
You may have a section of the roof that is perfectly fine, perhaps because it had been rethatched separately a few years earlier. In such cases, the newer thatch will gradually darken as it ages. Within a few years you won't even be able to find where the older and newer sections meet.
Though there are newer techniques for binding thatch to the roof laths, The Thatch Company believes that traditional thatched cottages should be conserved using traditional methods. Accordingly, the thatch bundles are "sparred on" to the roof. That is, a hazel or willow stick is bent and inserted deep into the thatch to hold it in place. The principle and use is exactly the same as a bobby pin on long hair. When inserted deep into the reed bundles, the wooden spar will hold everything in place. This is exactly the method used in the first place to build the thatched roofs that now require rethatching.
Thatched ridges need to be replaced more frequently than the water reed that makes up most of the roof. Plan on replacing the ridge every 8 to 10 years.
The Thatch Company