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Quality of materials
Long straw
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The variety
shall be recognised as suitable, or recommended as suitable if a new
variety. It will normally be a hollow stemmed, winter grown wheat,
although other materials are recognised.
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It shall have
an average cut length of at least 760 mm (30 inches)
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Whichever
method of threshing is employed, it shall leave the straw stem as little
bruised
and
broken as possible, removing cavings and all other rubbish.
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The
straw should be strong, supple and able to resist,
or even defy efforts to break it by twisting a handful continuously.
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Combed wheat reed
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The
quality of straw required is the same as that recommended for long straw.
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Providing the length of the straw does not fall below 685 mm (27 inches) it
is still suitable for combing, although the ideal length is 915 mm (36
inches)
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The straw
shall be suitable, if, on passing through the reed comber, comes out
undamaged, with grain and leaves removed and with all the stems laid in one
direction.
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No straw
should travel through the drum.
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Water reed
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Short reed
should be between 914 mm (3ft) and 1220 mm (4 ft)
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Medium reed
should be between 1220 mm (4ft) and 1676 mm (5ft 6 inches)
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Long reed
should be above 1676 mm (5ft 6 inches) with the majority of the reed around
1830 mm (6ft).
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The reed
strength should not be confused with hardness when the reed may also be
brittle. The reed should have a fibrous quality and should not break
easily. |
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Reed should
be grown in unpolluted area’s to avoid risk of disease to operatives and
degradation of the material.
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The bundle should not contain
more than 5% non reed plants.
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Sedge
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The quality
required of sedge is that the material shall be a leaf flattened at the butt
of not less than 13mm ( ½ inch)
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It shall have
an average cut length of at least 1m (39½ inches)
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The sedge
should not be brittle. It should be strong, supple and able to resist or
even defy efforts to break it by twisting a handful continuously after
dampening.
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The bundle
should not contain more than 5% non sedge plants.
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Ground work – material storage and preparation
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Stacks on
site should be covered to protect against adverse weather and raised from
the ground to prevent rising damp and stacked to prevent displacement and
risk of injury.
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Materials/components stored level to prevent distortion, damage and
crushing.
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All units
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Material
within the unit cleaned of damaged or foreign materials.
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Unit tied
firmly to avoid twisting and ensuring all material is well held.
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Unit size;
girth and length graded and shaped appropriate to required use.
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Long straw
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Material is
damped to be workable and loosely arranged to allow free drawing into units.
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Units be of
consistent density, length and without weakness throughout, all straws
within should be parallel.
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·Units have no
twists throughout, and are able to be handled without parting.
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Combed wheat reed
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·Units should
be cleaned of any damaged material, butted and then trimmed to clean exposed
ends.
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The units
should be lightly damped and allowed to steep prior to use. This damping
practice is not so essential when hooking on new work.
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Water reed
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Units should
be cleaned of any damaged or foreign material and butted to level out the
cut ends.
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Sedge
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Units for
ridge skirts and wrap over should be prepared as for long straw.
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Evaluate condition of roof structure
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Assessing working surfaces in accordance with requirements from bare roof
frame (new or recently stripped
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Main
frame is
complete, in good order and capable of accepting fixings.
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Internal roof
inspection carried out to determine if roof details are correct and existing
timbers sound enough to carry the weight and tensions of new thatch
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Roof
architectural details are sound and generally the pitches are 45-60
deg
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Battens are
of adequate strength and number.
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Tilting
fillets are correct according to type of material to be used.
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Barge boards
are sound and large enough to constrain the thatch, or act as tilting
fillets.
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Any abutments
which may cause problems or need additional work have been identified.
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Identify any
existing thatch that should be removed and any low or high areas are
rectified.
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Any gables or
eaves that need to be stripped out or replaced are identified.
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The condition
of exposed brickwork under old thatch is satisfactory.
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·Further
preparation or remedial work that is necessary is identified and recorded.
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·Any
historical items that may be discovered are notified to the relevant
persons.
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Checking for potential hazards (both inside and outside of roof)
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Any exposed
defective cables are identified and recorded.
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Any potential
fire hazards are identified and recorded, particularly defective masonry to
chimneys.
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Any pest
infestation or damage is identified and recorded.
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Any plumbing
works faults are identified and recorded.
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Any defective
timbers are identified and recorded.
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Any safety
hazards compromising scaffolding and ladders are identified and recorded.
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Loft hatches
to inspect interior and allow fire crews access are adequate to all bays.
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Preparation of roof prior to casing
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All old wire
to be removed
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All defective
or superfluous thatch removed in those parts to be replaced, chimney areas
to be stripped to allow examination of the stack.
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The
restoration of the base coat has been carried out where it was necessary to
part strip down to roof frame.
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High and low
parts filled in or out respectively and adequate to create a sound and level
work surface.
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The base coat
is the requisite thickness, density and is secured by relevant fixings, as
and where needed.
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Preparation of materials for fixing
Coppice materials
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Preparing
spars/brotches and liggers/rods from coppice materials.
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Spars/brotches for coating will not buckle on being used, be twistable and
be clear of snags throughout length.
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Be thin enough not to leave
holes in exterior use, not too long for task in hand and be sharply pointed
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Liggers/rods
will be straight, of even thickness, clean and of good appearance trimmed at
each end for flush lap jointing.
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Thick enough
not to bow between spars, thin enough to allow overfixing of spar twists.
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Thatching nails, screws and other fixings
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The type of
fixing shall be appropriate to the material and substrate.
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The length of
fixings will be adequate to hold the materials without damaging the
substrate.
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The strength
of the fixings will be sufficient to hold the materials without allowing
them to bend or move substantially.
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Sways are of
sufficient strength not to bow between fixing points.
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Position and secure thatching materials
Main roof
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Coatwork is
laid tight to sub-structure and the laid pitch angle formed is commensurate
with the pitch angle required for main roof.
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Cover over
fixings to be maximised without affecting pitch. At least: long straw 175mm
(7inches) combed wheat reed150mm (6inches) water reed (130mm 5inches)
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No course
marks or crossed materials, each course or layer applied to provide enough
kick for the next course.
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Minimum depth
of material above the batten or substrate, long straw 380 mm (15 inches)
combed wheat reed 305 mm (12 inches), water reed 305 mm (12 inches) casework
255 mm (10 inches)
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Sways applied
at a frequency so as to hold the top of the preceding course.
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Sways to be
tightened so as to maintain kick without crushing the materials or causing
them to kick up.
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Oversail
finished to level and even top, excessive kick to final course removed, top
course pitch maximised to roof pitch angle.
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Oversail
finished to the pitch of other side, top course thick and tight enough to
receive ridging spars, no voids between ridge rolls and oversail courses.
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Overall
thickness maintained throughout feature.
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Eaves and gables
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All units
fixed securely in the horizontal and vertical plane and fixed without
obvious joins or twists.
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Eave and
gable units fixed to give adequate overhang along complete length of wall
with consistent overhang commensurate with coat to be applied and dressed or
cut to at least 90° or undercut.
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Units fixed
tight to wall or sub-structure to give correct kick.
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Pitch angle
of material not too flat in relation to the roof, fixed to a consistent
density and tension.
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Apex units
fixed firmly maintaining consistent pitch with gable, so it does not kick
backwards maintaining a correct line with the main roof.
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Valleys
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Material
turned to align with centre line of valley with a rate of turn to give the
most effective dispersal of water.
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Rate of turn
is such as to maintain same density through valley consistent with the main
roof.
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Material
rounded to give minimum depth over centre of valley of: long straw, 406 mm
(16 inches) combed wheat reed 330 mm 13 inches water reed 380 mm (15 inches)
casework with long straw or combed wheat 305 mm 12 inches.
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Hips
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Material turned to align with centre point of hip.
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Rate of turn
is such as to maintain same density through the hip consistent with the main
roof.
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Rate of turn
is such as to maintain the tension through the hip, even density and
maintain cover over the fixings.
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Saddles
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Ridge
taken back to valley junction sub-structure
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Ridge
material at point of the saddle edge turned so as to carry water away from
the junction.
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Ridge pitch
maintained through valley junction at the pitch of the valley.
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Ridge
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Ridgework is
secure, with a pitch angle maintained throughout greater, or at least that
of the main roof.
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Rolls of
consistent size and density fixed securely and not deviate from apex.
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Knuckle or
butt courses fixed in pitch to main coat pitch or greater.
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Skirts laid
to consistent thickness and are additional to the main roof, skirts laid to
optimum thickness of 75 mm (3 inches) for a cut block finish.
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Skirts laid
to consistent density, well fixed and are fixed high enough to ensure
adequate cover over fixing.
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Wrapover is
fitted to firm and consistent density, of required pitch, effective
thickness, and fitted level and pointed on the apex (minimum 75 mm 3 inches
depth to the final roll.
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Butt up ridge
is (minimum 75 mm 3 inches depth to the final roll, additional to the main
roof, firmly jointed at apex and fitted according to prevailing weather.
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Block ridge pattern, the cut
should be firm, even and consistent with rod work, does not affect coatwork and is at 90° or greater to the ridge surface.
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Flush ridge
as wrapover with the lower edge merged seamlessly into the coatwork.
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Ligger work
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Spars not
easily withdrawn and not easily depressed, sufficient number of fixings to
hold externally each 150mm (6inches) length of material with a minimum of
three liggers per side.
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Correct
pattern placement determined with liggers parallel to ridge top line,
liggers parallel to cut line.
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Spars are
inserted at an angle so as to avoid the ingress of water, ligger work
sufficient to hold ridge stable and tight.
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Decorative
rod work is consistent and not excessive to the point that it impedes water
shedding.
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Forming joins between thatch and other structural materials
Box gutter
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Flashing is
adequately fixed with sufficient upstand, flashing is: seated to fitted
boards, carried into the roof horizontally to above the first sway and
vertically at least 230mm (9inches)
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Of adequate
size to permit cleaning, dressed to cover side flashings.
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Introduced
into the coursework at the sides with upstand to avoid water penetration,
dressed to ensure discharge of water.
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Applying thatch around vent pipes
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Lead, slate
or composite alternative is fitted over and around pipe; apron to front is
fitted over the thatch filled flush to under apron surface.
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Apron to the
rear introduced into coat at course pitch angle and taken back above the
fixing.
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Fitting stepped/side flashing
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Adequately
fixed with sufficient upstand, sufficient cover over thatch and abutment,
sufficiently overlapped with front apron, is sufficiently underlapped at
apex.
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Mortar fillets
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Mortar mix
allows effective, continuous adhesion; fillet has sufficient surface area to
masonry to allow effective continuous adhesion, thatch and masonry abutment
sufficiently covered.
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Applying appropriate finish for gables, eaves, main roof and ridges
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Cut or dress
eaves and gables to shape and correct line, trimmed and or plucked to tidy
finish with no cut marks and correct and consistent angle achieved.
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Coatwork
sheared/clipped/dressed/raked to an even finish, with no cut or course
marks.
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Surface of
ridge superfluous material trimmed above and between liggers/patterns.
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Applying protective netting to the thatched roof
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Correct netting selected for the material to be protected, netting to finish
flush to the roof shape, fixed securely throughout.
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All joints must be
secure, bird proof, of the correct type, without excessive overlap, correct
tautness and tension achieved and look tight. |
Very simple
sketch of thatching basics

If you are uncertain about these points see
Trouble Shooting & Surveys
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