SPECIFICATIONS



















        

STANDARDS AND SPECIFICATIONS OF WORK FOR THE THATCHING OF BUILDINGS IN EAST ANGLIA 

Part 1- Long Straw
Part 2- Water Reed

Revised and republished by The Standards Sub-committee of The East Anglia Master Thatcher’s Association
October 1998, April 2005, June 2009

 

PART 1 – LONG STRAW

Quality of the material

The Association recognises only good quality long straw grown especially for the purpose of thatching.  The guidelines for assessing quality are as follows:

1      Specification of materials

Long straw should be preferably hollow stemmed, winter grown wheat, although rye straw and its rye/wheat derivatives, such as Triticale are recognised. Rye straw should be noted as a less durable material, to some degree, due to the cell structure of its species.
There is no wheat variety, suitable for thatching, on the current NIAB seed list. Old seed must be retained and currently the main varieties in use are Maris Widgeon, Maris Huntsman, Aquilla, Square Heads Master and Masterpiece.

Where artificial fertiliser is employed, the Nitrogen level should be kept as low as possible, normally in the region of 50 units/acre for the modern approved varieties of wheat. For the older varieties of wheat that predate artificial fertilisers introduction, it is strongly advisable to keep the nitrogen levels down to below 30 units/acre, best applied as a balanced grassland fertiliser of NPK.

Crops are cut, traditionally, with a binder, when the nodes are still green and the grain is of a cheesy texture, this ensures that the straw is frozen in its prime, thus preserving it’s strength. The grain moisture content at this point is about 30%. The sheaves are then stood up, ‘stooked’, in the field to slowly dry and condition the straw in it’s prime condition, and to ripen the grain in the heads. This normally takes 2 – 3 weeks.
The straw should have an average cut length of at least 30 inches.

Whichever method of threshing is employed, it should leave the straw stems only slightly bruised, and not unduly damaged or crushed, avoiding the breaking of stems,

2     Traditional preparation

Long straw type material is composed from uncombed material, which is dampened and shaken onto a bed system.

It would be normal for a traditionally prepared bed to be thoroughly mixed, with no lumps of straw aligned the same way, in order to ensure that a reasonable mix of heads and butts can be pulled from the bed, when yealming.

A bed of straw should be of a reasonable size, or weighted, to help with a clean pull. Good double handfuls are then pulled out and laid side by side, to form a line of straw. Once a line has been made, bunches are worked tightly together, cleaned of waste and straightened to form yealms.

Yealms resemble straw tiles, approximately 18” to 24” wide and normally 4-5 inches in depth, but can be increased up to 7-8 inches. Yealms can be made tapered with a pronounced bigger end, for big end down thatching, or a more parallel yealm, suitable for big end up thatching.

3       Traditional application/ thatching to the roof

It would be normal to place the yealms into position, with a certain amount of sliding before fixing, without dressing into position. The ‘softened’ nature of this material, due to it’s preparation process, is important in allowing the material to ‘lie’ on the roof, without the need for dressing.

The long straw thatch when nearing completion should be raked through. Clipping should, normally, only be reserved for the eaves/gable edges and tidying up around the surface liggers. Shaving of the long straw thatch would be considered un-traditional and unnecessary.

It would be normal to expect to aim for an even mix of heads and butts showing on the surface of a freshly thatched roof, with an allowance of 10-15% dominance, of either heads or butts showing, being accepted as normal.

The three sections above define traditional Long Straw thatching. Where a different technique/style/method is employed, such as dressed/butt-ended/shaved straw, this should be made apparent to the consumer. It would be normal practice that the re-thatching of Listed Buildings be in the traditional Long Straw thatching craft technique. Application for membership to the Association shall only be by the traditional Long Straw thatching technique. 

New Work

Preparatory

  1. All old thatch and wire is to be removed where present.

  1. The roof frame shall comply with specifications for thatch.

Fixings

  1. The normal method of fixing will be by hazel, other wood sway or mild steel rod, sufficiently strong to avoid bowing between rafters.

  2. Sways will be either tied to the roof frame or secured using conventional thatching hooks of appropriate length.

  3. Every double course will be secured to every rafter.

  4. Sewing is recognised as a traditional method to be employed where circumstances demand it.

  5. Hazelwood brotches are recognised as appropriate to brow and half courses

The criteria to be employed at all times are that the material is to be fixed under tension and that it shall not slip.

Casework

  1. The material shall be tightly thatched and of an even density.

  1. The surface shall conform to the pitch of the roof and will not normally be less than 45 degrees.

  1. Eyebrow windows may exceptionally be reduced to a pitch of 40 degrees.

  1. The minimum thickness of the face work, measured above the face of the batten, at right angles to the rafter, shall not be less than 16 inches.

  1. Lining or backfill courses shall be employed as necessary to avoid the courses lying too flat.

  1. Face work thickness will be maintained through all features.  Valleys will be rounded out to give a minimum depth of 20 inches over the valley centre.

  1. The minimum depth of material over the fixings will be 6 inches but 6-8 inches will be normal.

  1. Flues may be cut, banded or rolled according to local style and custom.  The criteria shall be that there is an adequate overhang to protect the gable end, minimum 3 inches overhang at the board and 7 inches overall.

Recoating work

Preparatory

The removal of old thatch will vary according to region, for example the cut flue and the banded flue require different treatment.  The criteria is that surplus material will be removed down to a sound base coat of about 12 inches and that the basecoat be additionally secured e.g. by hooks and sways if necessary.  It will also be normal but not invariable to strip out old eaves and flues.

Renewal of Casework

  1. The material shall be tightly thatched and of an even density.

  1. The surface shall conform to the pitch of the roof and hollow areas thatched out.

  1. The minimum thickness of the new coating shall be 10 inches and this shall be regarded as the standard specification for recoating work.

  1. Face work thickness will be maintained through all features.  Valleys will be rounded out to give a minimum depth of 13 inches over the valley centre.

  1. Where for economic, technical or vernacular reasons the standard specification is reduced to 8 inches this should be made clear to the consumer.

  1. The minimum depth of material over the fixings for a standard coat will be 6 inches but 6-8 inches will be normal.

  1. The treatment of flues shall be in accordance with paragraph 8 above.

Fixings

  1. Where eaves and flues are renewed, the new bottles will normally be secured using hooks and sways.

  1. Elsewhere it will be normal to use hazelwood brotches of adequate length to secure the new coat to the old, with or without the use of straw scuds.

  1. Every course and half course shall be adequately secured.

The criteria to be employed at all times are that the material is to be fixed under tension and that it shall not slip.

Ridgework

  1. Ridges may be block or flush pattern, according to the local requirement.  All block ridges will be laid additional to the casework.

  1. Both types will be in pitch with the casework and adequately secured with long-rods, cross-rods and brotches.

  1. The final substrate, be it roll or twisted tops, shall be covered with a tightly packed turnover not less than 4 inches thick at the apex.

  1. Where a block pattern ridge is employed, the depth of cut, including ornamental pattern-work, shall be a minimum of 3 inches thick.

  1. Joints at chimneys etc, projecting from the ridge shall be weathered by adequate flashings.

The Association does not recognise the practice of cutting a block pattern out of casework thickness.

Netting

All areas of the roof will be securely protected by 20 gauge 19mm (maximum) mesh galvanised wire netting or polythene equivalent.

Netting shall conform closely to the roof shape and be fixed in such a way that it can be easily removed in the event of fire.

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Part 1 - Long Straw
Part 2 - Water Reed

PART 2 – WATER REED

Quality of the material

The Reed used shall be suitable for the task, mature and dense.  

New Work

The Association does not recognise the practice of ‘coating over’ with Water Reed.

Preparatory work

  1. All old wire and thatch to be removed.

  1. The roof frame shall comply with the specification for thatch.

Fixings

  1. The reed is to be secured by adequate fixings to ensure that there is no slippage.

  1. Every course of reed should be fixed to every rafter.

  1. The dimensions of the sway should be sufficient to ensure that there is no ‘bowing’ between rafters.

  1. The depth of material over the fixings will be a minimum of 5 inches.

Casework

  1. The Water Reed shall have a compact finish and even density.

  1. The surface of the reed will conform to the pitch of the rafter that will not normally be less than 45 degrees.

  1. The minimum depth over batten or substrate from the surface of the thatch will not be less than 12 inches.

  1. Face work thickness will be maintained through all features.  Valleys will be rounded out to ensure a minimum depth of reed over the valley rafter of 16 inches.

  1. Eaves and flues will be applied in the angular East Anglian  style and not ‘rounded off’.

  1. All junctions of ridges with reed casework e.g. gable windows, shall be adequately weathered by the use of a reed saddle piece.

  1. Soil pipes etc, piercing the casework shall be weathered by adequate flashings, sufficiently long to reach the sway.

  1. Box gutters to chimneys will be sufficiently large to prevent the accumulation of debris.

Ridgework

Material- good quality Long Straw or Marsh Sedge.

  1. All ridges will be of the block pattern, minimum thickness 3 inches, cut to shape if required and secured by liggers and cross-spars.

  1. A reed roll should be fixed to the apex and covered with a dense turnover of 4 inches minimum thickness.

  1. The ridge shall be in pitch with the rafters.

  1. Joints at chimneys etc, projecting from the ridge shall be weathered by adequate flashings.

Netting

The ridge will be protected by 20 gauge 19mm (maximum) galvanised wire netting or polythene equivalent.

If wire netting is fixed to reed casework, it should conform closely to roof shape and be fixed in order to ensure its easy removal in the event of fire.

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