The firm I work for frequently handles thatched properties and I am conscious of my limited knowledge of types, life cycles and costs. Indeed, in a number of cases, sale prices have revolved around the cost of thatch repairs. Can you help?
Some years ago a thatcher from south Hampshire called Bill Cleave, who now sadly is dead, was interviewed in one of the Sunday colour supplements and he finished his interview by saying “If anybody ever gives you a straight answer in thatching, he’s lying”.
Thatching is a very complex subject which does not lend itself easily to academic explanation — even the names of the three main materials in use in the United Kingdom barely describe the real origin of the material. However, it is essential when giving professional comment on thatched properties either to have a detailed knowledge of the subject or to call in an expert.
Let us start with the names of the materials.
Long straw, which historically has always been predominantly used in central and southern England, is the main winter wheat straw that has been cut with a binder and threshed. The material is not “longer” than any other wheat straw and is considerably shorter than other thatching materials. It is probable that it derives its name from the fact that the fixing method requires a considerable length of the straw to be visible on the surface of the roof.
The second material combed wheat reed or, as many people in the West Country would call it, Devon reed. Combed wheat reed is not, as the name implies, a “reed” but again winter wheat straw, which this time is combed in addition to being cut with a binder and threshed. This process removes about a third of the total weight of the harvest and leaves the wheat straw in a condition where it can be fixed in a similar method to reed — thus its name.
Norfolk reed is Phragmites Australis, indigenous to most parts of the world and by no means always coming from Norfolk, and should more properly be called water reed.
Long straw has a useful life in central, southern and eastern England of approximately 20 years, combed wheat reed a life of 30 years and water reed lasts for over 50 years. Each needs to be re-ridged at 10-to 15-year intervals but clearly represents different value as a roofing material.
These “ball-park” figures vary considerably, depending on a number of factors. Bath University has recently been given a substantial grant to research the early degradation of thatch in the West Country and it is hoped that some firm answers will be available in two or three years’ time. However, it is almost certain to be the result of a combination of climatic condition, clear air, pitch of roof, increased nitrogen content in the thatching material creating an environment for enhanced microbiological activity and probably several other minor influences.
This degradation frequently reduces life-expectancy figures to half those already mentioned and sometimes to even less. It is true to say that microbiological action that takes place where the thatch retains moisture is the prime reason for thatch deterioration, and the more rapidly the water can be shed from the roof the longer the thatch will last. Thus in a sheltered or shadowed position a thatched roof will not be expected to last as long as one in an exposed position where wind and sun can dry the roof quickly.
The Thatching Advisory Service have developed a chemical treatment to control early deterioration. This is more effective when applied to new materials but it can be used to destroy existing fungi. Moss and lichen growth can also be treated with chemical sprays. Such treatments are not permanent but regular attention should help to extend the life of a thatched roof.
There are many traps for the unwary surveyor to fall into, and although there are visual indications of types of thatched roofs, the only absolute test as to which material has been used is carefully to remove one stem from the roof and positively identify it.
When the thatch begins to deteriorate it is time to call in the expert. Thatch in very poor condition may need to be completely renewed, although on many occasions a useful extension of life can be achieved with re-ridging and patching. When preparing reports on thatch roofs it is important to be quite clear as to the current stage in the roof’s life cycle, particularly if it is showing signs of age. The roof area and complexity, such as eaves and dormer windows, chimneys and valleys, will all clearly affect cost, but the overriding questions pertinent to repair costs relate to date of last re-thatch, date of last re-ridge, frequency and nature of patching, current condition and future life expectation. The situation is further complicated by the fact that different parts of a roof may have been thatched in different materials and at different times.
Surveyors who frequently encounter thatched roofs would benefit from attending a structured one-day session in thatching, but even this will not turn a general practice surveyor into an expert and when in doubt, particularly on costs, the surveyor must refer the client to a thatching expert. Similarly, when advising on alterations and extensions to thatched properties, it is sensible to refer design details and specifications to a thatching expert for guidance.
Fire is a major worry for owners of thatched properties and, on occasions, for planning authorities. In the case of new properties greater protection can be achieved by using Barrier Foil 341. Not only does this provide a fire-retardant barrier between the thatch and roof structure but it also acts as a thermally reflective insulation. Also, on new timber the thatch itself can be dipped in fire retardant prior to thatching. The retardant has a life of about 10 years and ensures that in the event of fire the spread and penetration of flames is reduced.
Fire insurance itself used to, and still can, raise problems for owners and purchasers of thatched properties, but a number of schemes have now been specifically developed for insurance of thatched properties.
In response to a question of this type we could not possibly cover the full spectrum of possible answers. However, those frequently dealing with thatched properties should endeavour to learn more about costs, specifications, insurance, estimating age, fire retardancy, moss and lichen treatment and methods of fixing.
Further information and advice can be obtained from specialist companies in most parts of the country. We acknowledge the assistance of Thatching Advisory Service Ltd, of 29 Nine Mile Ride, Finchampstead, Wokingham, Berks RG11 4QD, in preparing this article. They run one-day seminars for surveyors and they will also supply free booklets on aspects of thatching.
