Water Reed Thatch

Water reed thatch is a roof covering made from the dried stems of common reed, Phragmites australis, a tall grass of rivers, marshes and estuaries, laid in thick bundles with the cut butt ends facing outward.³¹ In England it is often called Norfolk reed, after the reed beds of the Norfolk Broads where the traditional English supply was grown, and reed from elsewhere in Europe and Asia is sold as continental water reed; botanically they are the same plant.³ It is the most durable of the common thatching materials and gives a crisp, brush-like surface quite different from the softer, rounded look of straw thatch.¹²

The same material is the basis of thatching traditions in northern Germany, where it is called Reet or Ried, and in the Netherlands, where it is riet.⁵⁷

History

Thatch was the ordinary roof covering of rural England for centuries. By medieval times cultivated cereal straw, mostly wheat with some rye, was the main material in lowland areas, while in the Norfolk Broads and some estuarine and fenland districts reed beds were managed specifically to produce water reed.⁹ Coastal, moorland, heath and upland areas used wild plants such as marram grass, sedge, bulrush, bracken, heather and gorse, practices that have almost died out.⁹ Sedge, cut from the same wetlands as reed, became the usual ridging material for reed roofs because reed itself cannot be bent over the apex.¹⁹

From the late 20th century the balance shifted. Water reed spread well beyond its traditional districts as imports grew, and by the 1990s new thatched buildings in England were almost always roofed in it.¹⁴ In the Netherlands, demand for reed roofs on new and existing houses roughly doubled the area thatched each year between 1999 and 2007.⁷

The plant and its harvest

Common reed grows in dense stands in shallow water and wet ground around rivers, lakes and deltas, such as the Norfolk Broads and the Danube Delta in Romania.³ For thatching it is harvested in winter, when birds are not nesting and frost has stripped most of the leaf from the stems.³ Beds are cut every year, because if old stems are left, new growth comes up among them and the reed bends and becomes "dog-legged," which makes it unsuitable for thatching.³

Cutting was traditionally done by hand, a slow and labour-intensive but low-impact method, and is now commonly mechanised. Tracked harvesters do the most damage to the reed beds and are being phased out in favour of machines on flotation tyres that spread their weight on waterlogged ground, or walk-behind cutters, some of which also tie the reed into bundles.³ After cutting, the reed is bundled and stacked to dry, cleaned of leaf and short stems, and sorted by length and fineness; its moisture content should be below 20 percent before it is used.³

A typical bundle is about 60 cm (24 in) in diameter and 1.4 to 2 m (4 ft 7 in to 6 ft 7 in) long, and bundles are traded in bales of 20, 50, 75 or 100 depending on origin.³ An average house roof takes roughly 1,500 to 2,000 bundles, so a shipping container (up to 2,000 bundles) or a lorry and trailer (up to 3,500) carries about one roof's worth.³

Grading

Reed is graded by length, stem diameter, straightness and condition, because these determine how a roof is laid and how long it lasts.²³ English thatchers' associations use these length classes:²

Grade	Length
Short	914–1,220 mm (3–4 ft)
Medium	1,220–1,676 mm (4 ft–5 ft 6 in)
Long	over 1.7 m (5 ft 6 in), most around 1.8 m (6 ft)

Stem diameters range from fine (about 3.2 mm, 1/8 in) through medium (about 4.8 mm, 3/16 in) to coarse (6 mm, 1/4 in, or more); reed over 2 m long or with stems over 9.5 mm (3/8 in) is unusual enough to be flagged to the thatcher.² Straight reed is needed; reed with too much taper can lay back or over-tighten on slack pitches, and old, dull or brittle reed is avoided.²³

Sources of supply

Britain no longer grows enough water reed to meet demand.³ Imports rose rapidly from eastern Europe and beyond, while UK production declined, and many thatchers came to prefer imported reed as more reliable and marketed it as more durable and cost-effective than straw.⁴¹ Continental reed reaching Britain comes from Austria, China, France, Hungary, Poland, Romania, Turkey and Ukraine, among other countries, and is shipped by container or lorry.³ Historic England regards a supply of good-quality water reed, alongside cereal straw, as essential to the survival of traditional thatching, and its Traditional Thatch Project worked with reed producers on ways to increase supply.⁴

Construction

Roof frame and pitch

Water reed needs a steep roof. German practice treats 45 degrees as the minimum pitch for reed roofs.⁵ English guidance associates the longest life, 50 to 80 years, with frames of 50 degrees or more, and expects performance to fall on slacker pitches.⁸ East Anglia has a tradition of very steep thatched roofs; in the south-west of England, where pitches are generally lower, thatchers often lay water reed over a retained base coat.¹

Laying the reed

Bundles are carried up the roof and fixed in courses from the eaves upward, with the butt ends exposed.¹ Each course is held down by horizontal rods called sways, of steel, hazel or another suitable wood, fixed to the rafters with iron hooks, stainless steel screws, tarred cord or, traditionally, bramble rope.⁸ The recommended coat thickness depends on the reed: about 280 to 330 mm (11 to 13 in) for regular-length reed, 330 to 380 mm (13 to 15 in) for long coarse reed and 250 to 300 mm (10 to 12 in) for short fine reed, with sways spaced about 400 to 610 mm (16 to 24 in) apart up the slope and buried 115 to 130 mm (4.5 to 5 in) below the finished surface.⁸

The thatcher then beats the reed into its final shape with a leggett (or legget), a flat wooden bat with a ridged face, driving the butts up until the surface is tight and even.¹² Unlike long straw and combed wheat reed, water reed eaves are dressed into position with the leggett rather than trimmed with a knife.²

In northern Germany two traditional fixing methods are used: in the sewn method bundles are sewn to the battens with galvanised wire in several layers, while in the tied method rods press the bundles against the battens and are tied to them; willow rods and treated twine were used historically and have since been replaced by galvanised wire.⁵ Modern Dutch roofs may be built either on a traditional open batten structure or as a closed "screw roof" (schroefdak), in which the reed is screwed to a boarded, insulated deck; well-built examples of both show no relevant difference in lifespan.⁶

Ridges

Water reed is too stiff and brittle to bend over the apex, so ridges on English reed roofs are commonly made of sedge, which is rare on wheat thatch.¹² A new sedge ridge is mid to light brown, while a new straw ridge is yellow; once weathered they are hard to tell apart.² Ridges need attention far more often than the main coat, typically every 10 to 15 years.¹ In Germany the ridge is likewise the weak point and may be capped with layers of turf or heather held by crossed sticks, or with twisted straw ropes.⁵

Rethatching

When a water reed roof wears out it is normally stripped back to the roof timbers before the new coat is laid, unlike straw roofs, which are often recoated over older layers; the south-western practice of keeping a base coat is the main exception.¹² Stripping gives an opportunity to repair or add rafters.²

Durability

Water reed is the most durable thatching material.¹³ A Norfolk reed roof in East Anglia has been expected to last on average 50 to 60 years, and many water reed roofs have lasted at least 70 years.¹² Lifespans of 25 to more than 40 years are more typical in general, with several roofs over 60 years old known.³

About half of a reed roof's potential life depends on the quality of the reed, about a quarter on the pitch, and the remaining quarter on all other factors combined.⁶ The governing principle is that the drier a roof stays on average, the longer it lasts:⁶

• Steeper roofs shed water faster and dry more quickly.
• Long roof slopes collect more water and stay wet longer in their lower half.
• East- and south-facing slopes dry faster than west- and north-facing ones, where deterioration usually appears first.
• Shade, shelter from wind and drips from overhanging trees slow drying; drips from a tree can cut a roof's life by up to half.
• Leaves, pine needles and algae hold moisture.
• Valleys and dormer tops have flatter angles and wear faster, so complex roofs generally have shorter lives.

Fire safety

Reed burns readily and is vulnerable to sparks and flying embers, so German building authorities impose minimum separation distances for reed roofs.⁵ In England many thatchers recommend fitting a fire-resisting board beneath new thatch that gives at least half an hour's fire resistance.¹

Conservation

In England, water reed has long been dominant in the Norfolk Broads, the fens and estuaries, while lowland areas elsewhere traditionally used cereal straw: combed wheat reed in the south-west and threshed long straw across most of the rest.⁹ New thatched buildings are almost always covered in water reed.¹ Replacing long straw or combed wheat reed with water reed on a listed building changes its historic character, and numerous planning appeals have found such changes harmful; Historic England advises that any change of material should be clearly and convincingly justified, and listed building consent is required.⁹¹ Local authorities may tie repair grants to compliance with their thatching policies.¹

Regional practice

• England: traditional in Norfolk and the fens, and widely used in East Anglia and parts of the West Country; now the usual material for new thatch.⁹¹
• Netherlands: more than 150,000 thatched homes were estimated in 2010, plus many outbuildings; about 350,000 m² of reed roof was laid in 1999 and about 700,000 m² in 2007, and the number of thatching firms grew from 280 in 1999 to 425 in 2008.⁷
• Northern Germany: reed roofs are a characteristic part of the coastal and rural landscape, laid at 45 degrees or more.⁵