Thatch roofing - The construction
Thatching makes use of materials that are naturally available -
grass or reed.
The stalks of thatching grass are normally hollow and about 3 mm
thick. Dekriet stalks, however, are solid and about 3-4 mm
thick. The quality of the material improves with cultivation and
regular cutting. Some thatchers consider that the quality of
material that is cut by hand is superior to that of material cut
by mechanical means. Hand cutting will produce about 50 to 100
bundles a day. A mechanical cutter and binder will process about
6000 bundles a day.
After cutting and loosely bundling, each bundle is shaken
briskly to dislodge all loose material. The bundles are then
cleaned by passing a sickle through them. This removes the
remaining leaf growth from the lower two thirds of the stalks.
The grass is then remade into bundles. These bundles are each
tied with a thong of twisted grass or with twine and packed in
heaps about 2m high and 3 m in diameter at the base.
When the thatch is to be used for the area immediately above the
thatching battens, where the underside will often be exposed
within a room, the material should be combed to ensure that the
stalks are perfectly clean. A comb is made by driving a number
of round wire nails into a approximately 300 mm length of
The thatcher in general thatch construction normally uses five
- This is used for hand cutting as well as for cleaning the cut
The thatching spade
- This is usually a home-made implement consisting of a board
with a handle on one flat side, rather like a plasterers float.
Several metal blades are secured to the other flat side. This
tool is used to dress and shape the thatch in position.
- When it is possible to have an assistant working on the
underside of the thatch, a straight needle, about 300 mm long,
is used to 'stitch' the thatch to the roof battens.
A curved needle
– It is used to 'stitch' the thatch to the roof battens when it
is not possible to have an assistant working under the roof
A climbing hook
- S-shaped climbing hooks are used to give the thatcher a foot
rest when working on the roof slope.
A typical small thatching team consists of four men; one to pass
material from ground to roof level, two thatchers working on the
external roof surface and one working under the roof to assist
those working on the outside. Such a team can be expected to lay
about 10 m2 of thatch in a day. Before each bundle is passed to
the thatcher on the roof it is butted against a butting board,
or on level ground, to ensure that the butt end is even and that
any sharp ends are blunted. The bundles are normally thrown up
to the thatcher. The grass is used in bundles as cut and laid on
the roof with the butt end lowest. As each bundle is laid on the
roof the thatcher cuts through the twisted grass or twine that
secures it. He lays the first bundle on the corner, at an angle
of at least 45°, thus exposing the butt end at the eaves and at
the verge. Each bundle in the first course at eaves level is
secured to the second batten with tarred sisal cord thatching
twine at 75 mm intervals. In this process of stitching the
straight needle is used, where one man can work under the roof.
If it is not possible to work under the roof the curved needle
is used. Subsequent courses are secured, either with a poplar
stick or with a length of 4 mm diameter galvanized steel wire.
The thatch is laid, two bundles thick, to a total minimum
thickness of 150mm. Each successive layer conceals the poplar
stick or wire that secures the previous layer. As thatching
proceeds a layer of selected stems is spread evenly on the roof
battens to a thickness of about 12mm. This gives a neat
appearance inside the roof. On top of this layer a laminated
foil of aluminum and building paper reinforced with fiberglass
is laid as a protection against fire. Thatching then proceeds,
course by course, to the ridge level until complete.
Thatched roofs are generally constructed with dripping eaves;
rainwater gutters and downpipes are not normally provided.
Eaves overhangs should be at least 600mm and some provision
should be made at ground level, around the building, to prevent
erosion due to water dripping from the eaves. This can either be
in the form of a concrete apron or paved surround.
A thatched roof will normally last for about 25-30 years if
properly laid. Aesthetic advantage of using a thatched ridge has
been mentioned previously. A disadvantage of using such a ridge
is that it will require renewal every 4-6 years. As maintenance
of a thatched roof invariably results in dust and pieces of
straw being dislodged from the roof, the provision of a
reinforced cement ridge, suitably waterproofed and coloured, may