The availability of thatching materials and their quality are ongoing issues for the conservation and thatching sectors.
There are no regulatory standards for thatching material, but advice is given in numerous thatching guidance publications.
Problems with the quality of straw in the 1980s, lead to pressure to use water reed, which is subtly changing the appearance and character of many historic buildings and villages. Increasingly, the demand for thatch is being met by imported materials.
In most projects thatchers will supply their own materials. Through knowledge and experience they can judge the quality of the material through provenance and inspection before purchase.
The characteristics of good quality thatching materials
Thatchers and growers also have different opinions of what constitutes good quality straw. A grower seeks a crop that will produce a high profit margin per acre with minimal inputs, is disease resistant, will not fall over (lodge) in wet, windy weather and fits in with other farm operations.
Thatchers will assess straw using the following criteria and select the ideal:
- Length: 100-130 cm.All modern commercial wheat varieties are too short to be used as thatch. Stem length has been halved over the past 150 years from 140 cm to c. 70 cm. Taller ‘modern’ varieties used for thatching (eg. Maris Widgeon 1964) produce short (80 cm) straw when grown in low nitrogen conditions, whereas late 18th and early 19th century varieties (eg. Squareheads Master and Little Joss) grow to 110-120 cm. Slightly shorter straw (but not less than 85 cm) can still produce good quality long straw.
- Coarseness (combed wheat reed only): medium to coarse.Stem diameter is more critical for combed wheat reed-style thatch than long straw. Fine-stemmed straw will leave an attractive surface finish, but a coarser straw will produce a less ‘polished’ surface that dries out more quickly after being wetted. Coarse straw is preferred for areas of a roof that receive more surface run off eg. valleys.
- Straightness (combed wheat reed only): straight with minimal dog-legging.Straw with straight stems is preferred for combed wheat reed because it produces a smoother surface finish. Dog-legged straw, which has a kink at the butt end, is more difficult to dress into place and leaves a more open finish – but this can be an advantage in damp situations. Dog-legged straw can still be used for making ridge rolls, eave bottles and for backfilling.
- Strength, hardness & flexibility: strong but still flexible.The strength and hardness of a straw is one of the best measures of its probable durability. Strong straw will have a thick stem wall and can be dressed with a legatt without ‘starring’ (breaking) the butt end. Straw that ripened (lignified) fully before it was cut is brittle and easily broken when dressed. Thatching straw also needs to be flexible. Strength and flexibility are measured by twisting a few strands of straw into a coarse rope – durable straw produces a strong and flexible bond, whereas brittle, over-ripe straw snaps.
- Colour & waxiness: pale with silvery sheen & waxy surface.High quality straw is usually pale coloured with a ‘silvery’ sheen and a ‘waxy’ feel. Straw grown with too much nitrogen fertiliser is usually bright yellow and very shiny, and will discolour quickly on the roof. Wax on the surface of the straw is a thatched roof’s first defence against decay, and will vary from year to year depending on genetic and climatic factors. Waxy combed wheat reed is easier to dress into place and sheds water rapidly. Chemical herbicides and fungicides interfere with wax production and can strip wax from mature stems.
- Leafiness: essential for straw, but few leaves at butt end best for combed wheat reed.Combed wheat reed that is clean at its butt end is easier to apply, produces a neater finish, and will last longer because it will absorb and retain less surface water. Residual flag leaf at the top of the stem is not usually a problem because this is buried beneath the fixings. Combing machines vary in how thoroughly they strip leaves, and wheat varieties vary in the size of their leaves and how easy they are to strip. In contrast with combed wheat reed, leaves are an important component of good quality long straw, and are not stripped when straw passes through the drum of a threshing machine. Leaves absorb water when the crushed straw is heaped, wetted and drawn into yealms (bundles) of long straw, and add essential cellulosic ‘bulk’ to the thatch which greatly improves its durability.
- Taper: moderate.Well tapered straw allows a thatcher applying combed wheat reed to cover a greater roof area with a standard weight of straw. This is an advantage for the thatcher, but a thin coat of short, tapered straw will not last as long as a thicker coat of less tapered straw applied to the same pitch. A good taper also helps produce a well-shaped yealm of long straw.
- Smell: sweet without mustiness.Good quality straw has a distinctive, sweet smell without the ‘mustiness’ that develops when straw hasn’t been stored properly or has been fouled by rodents.
- Grain content: no residual grain.Good quality thatching straw should contain very little grain. Residual grain in the surface layer of long straw will sprout and die back, leaving dead root systems that can help channel water into the core of the thatch. Dead grain is also a source of nitrogen that will stimulate decay. Residual grain is less of a problem in combed wheat reed because the ears are buried deep within the new spar coat. However, in both combed wheat reed and long straw residual grain is a magnet for mice and rats who can cause immense damage as they nest and forage.
- Growing season: preferably winter wheat, sown in October-early November.The best quality straw is grown from hardy, traditional ‘winter’ varieties of wheat planted in October-November, and cut in early-mid July while the stem is still slightly green. Early planting allows the plants to develop a larger root system, which in turn stimulates tillering and produces a taller, and thicker-stemmed, straw. Quality always reflects the growing season, however, and an ‘intermediate’ winter wheat planted in good conditions in early February (or an older spring wheat planted in February or March) can produce better quality straw than a disease ridden, autumn-sown wheat that has been damaged by a very cold or wet winter.
- Processing: no weeds; stems uncrushed with no short straw for combed wheat reed.The stems of combed wheat reed should not be crushed during combing, or when the reed is bound and clamped prior to storage and delivery. Both combed wheat reed and long straw should be as free of weeds (especially thistles) as possible. Good quality combed wheat reed should not contain many short or broken stems, whereas short stems add essential bulk to good quality long straw.
- Storage & delivery: straw stored on pallets; delivered in compact, and securely tied, bundles.Straw should always be stored on pallets rather than directly on damp soil or concrete floors. Both combed wheat reed and long straw should be delivered to the thatcher in compact, and securely tied, bundles.
Click to close
› Click here to read an article about the availability of thatching materials.
Click on any of materials to read more about each one:
› Click here to read more about species and varieties of thatching cereal in the U.K.
Modern wheat is grown primarily for its grain and is harvested with a combine harvester. Wheat crop has been transformed by plant breeders who have purified and hybridised wheat in order to create new varieties with greater yields and baking qualities, and with shorter stems to carry the heavier ears. Consequently, most modern wheat varieties are now too short to be used as thatch, and straw has become a waste product, rather than a valued by-product, of grain production. The availability of straw suitable for thatching has plummeted. Problems with straw quality in the 1970s and 1980s highlighted the presence of too much nitrate due to the use of fertilizers which caused accelerated microbiological decay.
The problem has been exacerbated by regulations that prevented the marketing of seeds of certain wheat varieties. This meant that by 2009 only two varieties of wheat suitable for producing thatching straw could be sold or exchanged. The regulations have now been amended to remove some of these restrictions, so it is hoped that there may be a revival of some of the old varieties that produced far more robust thatching straw.
Today, thatching straw is grown by specialists using low input or organic production methods.
Thatching straw is a sustainable and environmentally friendly crop that can be grown locally for use by craftsmen roofs. It can also provide a profitable alternative crop for many small and medium-sized farms and increase rural employment. One acre of thatching wheat will produce 1-1.5 tons of straw (and an equal amount of feed quality grain), which in recent years has sold for c. £ 850/ton. However, growing straw is labour intensive, requires storage facilities and specialist knowledge and equipment.
› Click here to read more about growing, processing, buying and selling thatching straw.
Straw growing trials are currently being undertaken to learn more about the properties and performance of some of the different wheat varieties that are suitable for thatching.
DEFRA produce monthly reports on wheat production: http://www.defra.gov.uk/statistics/
Click to close
Water reed was historically harvested by hand. In the early 19th century reed combing became mechanised and by the turn of the century developments allowed bundles of clean and threshed reed to be produced on a large scale. It became the most popular choice of material by the 1960s due to the belief that long straw and combed wheat reed were inferior in their quality and longevity and irregular supply.
It is true that many steeply-pitched roofs in (dry) East Anglia that were thatched with top-quality Norfolk Reed in the early 1900s survived for over 70 years with regular maintenance and re-ridging, but many roofs thatched in recent times with poor quality imported water reed have failed in less than 10-15 years. A roof thatched with Norfolk reed, or top quality imported reed, can no longer be expected to last for more than 30-35 years.
Up until the 1970s, Norfolk water reed was readily available. However, concern about the effect of regular harvesting on wildlife led to a decline in wetland management and consequently water reed production. But recently it has been found that management of reed beds in fact benefits the ecology and regular harvesting of reed beds is now proving more viable.
The main supply of UK reed still comes from the Norfolk Broads, but this is insufficient to satisfy modern demand, hence the majority of water reed is imported from Europe.
Water reed harvesting in Wales:
Master Reed Cutter Eric Edwards talking about harvesting reed by hand:
Click to close
You can read more about water reed and sedge cutting at the website for the North Norfolk Reed Cutters and the Broads Reed and Sedge Cutters Associations: http://www.norfolkreed.co.uk/
Click to close
The spars and liggers used in thatching are mainly made from hazel (Corylus avellana). The hazel is managed by a system known as coppicing, whereby the stems are cut low down promoting re-sprouting of multiple stems, which are harvested on a seven year cycle, ensuring an ongoing supply of timber of the correct diameter. In the past, thatchers sometimes cut and prepared their own spars during the winter months.
Hazel is available from English woodlands. When managed to Forestry Stewardship Council standards, it is a good quality, durable material, produced in a sustainable way. Sustainable coppicing creates rural employment opportunities and helps to ensure biodiversity.
There are several websites dedicated to hazel coppicing, where you can find out more:
Click to close