Laying Standard Thatch Coatwork


This page explains the process of thatching Straightwork, that is areas of roof without any Features

Long straw straightwork thatch

Straightwork… once away from the gable end feature of the barn, this 1930’s thatcher had a great deal of straight coatwork to thatch. It can get rather daunting, especially if working by oneself.



Before we begin it might be as well to recap, on the basics of Standard thatching; as detailed in the Beginners Guide page…

A roof covered, using the Standard method of thatching consists of layers of thatch, commonly known as Courses; which are held in place by Fixings. Standard thatching needs replacement or repair, when it has worn back to where the thatch is held in place by the fixing. The skill of the thatcher is to delay this event for as long as possible. By completing each course correctly, they should achieve two things…

a) Keep the thatching material as steep as possible, within the coatwork, to shed water more effectively. The courses of thatch are usually around 6 inches (150mm) thick; depending on the type used. A suitable angle of material within the coatwork, of around 20 degrees, can be maintained by the skilled use of some Backfilling. This is extra material, added when necessary, which in effect thickens the top of the new course, above the fixing, making the succeeding course lie steeper. (This correct angle of thatching material should not be confused with the pitch of the roof. The angle of roof pitch is determined by the roof structure itself.)

b) Enable the fixing to be put back as far as possible, from the outside of the thatch, thus giving the roof its maximum life. With the correct amount of thatch in place, the material can be fixed, between 15 and 20 or so inches (370/500mm) up from bottom of the thatch. Without the lower part of the thatch becoming too slack.

Section of Coatwork

Close up… How courses of standard thatch should lie in a roof; for maximum longevity

If the thatch is being laid properly and is following the pitch of the roof; there should always be a constant Depth of Fixing of around 6 to 8 inches (150/200mm) of coatwork above the fixing. The amount of thatch below the fixing can vary, this being determined by the length of material and any backfilling, giving an overall thickness of anything between 9 and 15 inches (225/375mm) to a thatch roof. A perfectly good coat of combed wheat reed could have the lower measurement; a roof of long water reed the upper; with each having the correct depth of fixing in place.
This depth of fixing is a vital measurement. Thatchers often check it; by using the distance across their hand with the thumb extended. This is the working part of the thatch that will wear away over time. The temptation is create more of it. But creating a roof too thick is as bad as having one too thin. If the courses of material are too thin, the fixing has to be brought forwards, towards the outside of the coatwork; to create a firm roof, thus shortening its life. Too thick, and the courses of thatching material will lie too flat; and allow water to run back up the thatch, instead of running off it.

2gInside a Standard thatch roof… Showing the courses already fixed, and those ready to be extended.

Along the course, or up the lane… Which way to go?

There are two ways of proceeding to thatch a roof; each having advantages over the other…

One method of working is to proceed up the roof in strips; of between 30 and 36 inches (750 to 900 mm) in width… (as shown opposite) The exact width being determined, by how far the thatcher can comfortably lean over their work. As ever, these strips have more than one name. Stulch is used in the eastern side of England, Lane being a term from Devon.

thatching devon

Devon Lanes… This image from around 1930, shows some Devon combed wheat reed being laid. The rope top ridge points to a location in South Devon. At this period, if working alone, thatchers often ridged as they progressed across the roof. Note the sparred ligger along the eaves, similar to long straw work, but used in this case to strengthen the bottom of the roof. Another common working practice from years past…

thatching devon

This method is ideal for a thatcher working alone. The thatcher’s ladder does not keep digging into the partly completed thatch. So the coatwork needs less tidying up, at the end of the job. The thatcher can also look down and across the completed strips; to check for a correct line. And only a small portion of old roof need be exposed, while work is completed. A useful advantage, in a maritime climate…

devon thatchAn ideal working method, if several thatchers are working together, is to proceed across large sections of the roof; with only one or two courses of coatwork at a time. (as shown opposite) The work can be broken up, with each thatcher following the other. One laying, one driving and one fixing for example. If organised properly, this is a very fast way of thatching. Water reed lends itself well to this method. Especially when creating a single layered thatch… Several thatchers can cover a large section quickly; without getting in each other’s way.

19dAt the start of each new strip or section of roof, it is good working practice for the thatcher to Open Up all the courses, in the edge of any previously thatched area of roof. This consists of lifting up the edge of each course, thus allowing any new courses of thatch to slide partly under the old ones. The reeding pins, long thatching crooks or spars; that temporally held the edges of these courses, are now used to hold up this lifted edge. And will in turn be used again, to hold the edges of the new layers. This lifting creates a zig zag effect to any join. This is good working practice, as wider joins spread the rain drops, straight ones can concentrate them.

Not all thatching follows the same style. A main difference is found at the bottom of the roof, in the treatment of the eaves. As a general rule, the further west you travel in Britain; the more curved the eaves are… The sharp angles found in eastern eaves, are caused by having more overhang over the wall and strictly following the pitch of the roof, as soon as the first full course is fixed. Curves are easier, if a little less overhang is created, and the first couple of courses don’t quite obtain the true pitch of the roof…

19e Eastern sharp lines at Blicking in Norfolk…
19fWestern curves at Puddletown in Dorset…

All standard thatching in cereal straw begins with an eaves layer of tied bundles. This creates a solid base, when the edges of the roof are later trimmed. With long straw, these bundles are called Bottles. The thatcher makes these by yealming a bundle of material, around twice the size of a normal yealm. With extra large, large ends, to give more taper. These are tied, with either a cord or a straw bond. They are positioned to overhang the wallplate, by half their length. Usually giving a final overhang, when trimmed, of between 15 to 18 inches (375/450mm). These bottles are normally tied or fixed with thatching crooks into position.

When using combed wheat reed, these tied bundles are known as Wadds. Again they are double handful sized and overhang the wall, by between 12 and 15 inches (300/375mm). And are fixed in the same manner as long straw bottles.

The only bundles used with water reed, are the ones already graded by the thatcher… No wadds or bottles are used here. Generally the eaves layer consists of some Fine short bundles; overhanging the wall by 15 to 18 inches (375/450mm). The thatcher fixes these loosely then shapes the reed, with a legget, into an eave.

The first course of thatch, with all three materials, is laid at around half the thickness of a normal course; being known as a Brow Course. This has the effect of creating more springing, at the bottom of the roof.

This, and succeeding courses are held in place by fixings. The type of fixing used depends on what the thatch is being attached to. When thatch is being attached directly to the roof timbers; a Single Layered roof is created. Here the material is held in place by a Sway; a long piece of split wood, or more likely steel bar. Often a hooked steel spike or Thatching Crook is then used to fix down this sway; a crook being driven into each rafter, along the length of a course of thatch. Alternatively a wire is screwed into the rafter and then tied around the sway.

Or, if the previous layers of thatch are used as a base to fix the new; the roof becomes Multilayered. Then new coats of thatch are invariably held in place, by twisted and pointed wooden pegs; Thatching Spars. These are driven through the new thatch, into the old layers beneath. With water reed a straight spar is used in a similar fashion to a sway. But with the cereal thatches a continuous straw bond is used when Sparring on a thatch. This is created by taking a little material from behind a fixed spar and bringing it over and across the new work; sparring it down every few inches or so; until more is required…

When sparing down this bond, it is good practice to drive the spars in Uphill. That is keeping the spars pointing horizontally or slightly up… So they will not draw water into the roof; hopefully decades in the future; as the roof wears back to this line of fixings.

 

2fWhen using water reed and combed wheat reed thatch, this and succeeding courses of material are driven into place, with the thatcher’s legget. (As shown opposite) The long straw thatcher never needs this tool, simply laying the prepared yealms of thatch into place. As work proceeds the long straw thatcher uses a side rake to clean and gently tap the new coatwork.

With the brow course complete further full sized courses are now laid.

Typically a main course of long straw is laid thus… Having a yoke full of yealms at hand, with all the large ends towards them, the thatcher takes one yealm at a time and with the large end downwards, lays it on top of the previous layer… This new course of yealms should cover the previous course, by two thirds. The yealms should be snug against each other. The thatcher running their hands between each yealm cleaning the join; and gently pushing the two together at the same time.

The courses of long straw should not be allowed to get too flat. In effect having too much springing… This is remedied by turning the yealms around, so that the thicker large end lies behind the line of fixing; thus making the material steeper once more. The two thirds overlap on each course, gives the coatwork its optimum thickness. The line of fixing is positioned, to catch the top butt ends in the yealm; around 15 to 18 inches (375/450mm) up from its bottom edge.

Typically a main course of combed wheat reed is laid thus… The neat way the tier packed the bundle, during combing, can be utilised; by cutting the bundle at the tier’s knot. The wheat reed then lifts out cleanly, in the reverse order in which the bundle was formed. The thatcher takes around a fifth of the bundle; whatever’s manageable, and cradles it in one arm with the butt ends down. Then gently drops it down against the roof several times, to level the material.

The reed is then laid, slightly overlapping the previous layer; and the correct thickness of the course established. This is around 4 inches (100mm) in depth. The reed should be firmly packed, but not overly so. Further amounts are then laid in place. Unlike long straw thatching, here there is much still to do; before the course is fixed. The wheat reed is firstly tapped roughly into position, with the thatcher’s hand. Any rubbish is now removed, by running the fingers through the straw. This done, the thatcher now puts some pressure onto the new work with one arm and with the other drives the reed into its final position, with the legget. Always following the pitch of the roof. A lip is left on top of the driven reed, to merge into the next layer. This stops the layers of thatch appearing as lines in the finished coatwork.

Combed wheat reed is fixed between 15 to 18 inches (375/450mm), up from the lip. Often the distance from the thatcher’s fingertips to elbow, is used as a measure; what the ancient’s called a cubit… With the correct amount of wheat reed in each course, (around 4 inches/100mm), driven off to the correct pitch; there should be 12 inches (300mm), between each of the straw bonds or sways holding each course. And more importantly, 6 inches (150mm) from the sway or bond, to the outside face of the coatwork. Thus producing an ideal depth of fixing. When the thatcher achieves any three of the above measurements; they will always have the fourth…

Typically a main course of water reed is laid thus… The thatcher lays bundles of reed, butts down, so they overshoot the previous course a little way. These are then opened. Of the three main materials only water reed needs a temporary fixing, once the bundles are opened; as it will slide off the roof at will… A few pieces of reed laid across the bundles; held down by long thatching crooks, usually does the trick.

Once opened, the joins between the bundles should be cleaned and rubbish removed. Then, with one arm across the reed to create some pressure, the thatcher drives the material into place. As with combed wheat reed, a lip is left to join into the next course. Unlike combed wheat reed, the legget is used for all driving. The butts of water reed should be too hard, to attempt any driving off by hand. When driven off, the course is fixed.

Good Medium grade water reed is used to thatch straightwork. This longish reed keeps the amount of springing under control. Stopping the coatwork from becoming too flat. But backfilling can also be used, where the thatcher only has short reed at hand.

As with the other materials, the thatcher should ensure the lines of fixings are either square on with the ladder; or run parallel with the roof battens. The courses, basically one bundle deep, are thicker than found with wheat reed and the line of fixing is often set further back. Anything up to 2 feet (600mm) is normal. The overall thickness is determined greatly, by the length of reed used. And the important depth of fixing is often a little more than 6 inches (150mm); but should not greatly exceed this distance.

The coating then proceeds towards the ridge. Most roofs have more than ten courses and less than twenty… As wheat reed is shorter than water reed, it can soon lie rather flat in the course; a case of too much springing. This is remedied, by the almost constant use of backfilling. Which thickens up the thatch above the line of fixing. Often old thatch is used, as backfilling is never exposed to the weather. The wheat reed thatcher has to be constantly aware of this potential problem. And all thatchers have to regularly check, that the roof is following the correct angle or pitch of the roof; as well as the correct thickness and shape…

As mentioned in the page on preparation, a large ridge roll should already be fixed to the ridge board, on any bare timbered roof. Multilayed thatch mostly does not require this. With all materials, the courses are thatched so that the bottom edge lies up to around 3 or 4 feet (900-1200mm), from either the top of the ridge roll or an existing roof. Any over sailing thatch is then removed. A second smaller ridge roll is then fixed.

There is now one final course left to thatch in. This very top course is usually laid in one go, all around the roof; after all the other coatwork has been completed. The thatcher using it to level up the roof, ready for ridging. Thus it is sometimes known as the Levelling Course or Top SettSett being a West Country name for a course of thatch.

The width of this top layer varies. In eastern areas they thatch up as far as possible. Leaving a very narrow strip, between the top edge of the coatwork and the position of the ridge roll. In the West Country, a strip of between two and three feet (600/900mm) is left. This difference comes about, due to the use of different ridges in different areas. The Flush ridges, more commonly used in the west, should not have the coatwork face going under them, as this will leave an unsightly line along the bottom edge of the ridge. Ornate block type ridges, which seem to have been invented in the eastern counties of England; don’t have this requirement. So ideally, the thatcher should judge the width, to suit the ridge…

19u

Unsightly line… this piece of flush ridging is spoilt at the bottom edge. As the coatwork face continues on underneath it.

The fine details of ridging will come later… After all the Features, that complicate thatcher’s lives and make thatch so attractive, have been dealt with…