ASSOCIATIONS
The backbone of a thatched roof
Numerous thatching companies enter the market annually due to
the low capital outlay required, only to disappear again after a short
period leaving behind a trail of sub-standard roofs and bad debt.
By Thatchers Association of South Africa (TASA)
10 JUNE / JULY 2019 //
O
nly in recent years have certain municipalities made
it mandatory that a structural engineer is
responsible for the construction of thatch roofs – a
misnomer as all other structural elements of a building have
always been subject to this requirement.
Many roofs, including thatch roofs, are still constructed
today without the approval of a specialist engineer which
can result in major expenses to the consumer, sometimes
many years after construction due to age destruction
(tearing of fibres in the timber from overloading). Age
destruction of the pole structure, if under-designed, can
cause building walls to crack or collapse and in the worst-
case scenario the entire collapse of the roof. The rate of age
destruction is dependent on the percentage overload to the
structural element.
The level of competency of new incomers into the
industry as well as the changing characteristics of the raw
material, have an enormous effect on the quality of the end
product. The design and pole construction of a thatch roof
are the backbone on which the ‘meat’ is hung, and the
carpenter must make it successful.
As in the case of a thatcher, the thatching industry is one
of the few offers informal craftsmanship for carpenters
starting as a regular labourer and working his way up with
an experienced carpenter. This process takes at least five
years and more and through experience of how construction
problems are tackled and figured out, he learns for instance
the complex stress factors to which poles are exposed.
Rafters for thatch roofs are not assembled in a factory
beforehand, but different thicknesses, lengths and
classifications of poles are delivered on site.
A labourer starts by carrying poles and learns what
classifications, thicknesses and lengths of poles are being
used for which purposes. He learns the names and to use
the different tools and learns the names of the different
pole structures.
As the labourer gains more experience and knowledge,
he gradually progresses to learner carpenter and assistant
carpenter by learning for instance: the setting out of the
pole structure, timber requirements, planting posts, upright
columns, king posts. Rafter, truss and tie beam spacing and
positioning of the ring beam. Connections, battens and
laths, lath spacing and how to construct valleys and hips. He
must not be afraid of heights and learn to put scaffolding
together and remove it again.
Most carpenters have a ‘team leader’ or senior carpenter
who has been working in the industry for about 10 years
who mentors and trains junior carpenters. It takes at least
The design and pole construction are the backbone of a thatch roof.
five years to train a junior carpenter up to a level that he
can build small structures such as for rondavel or lapas up
to 6m x 6m including a half metre overhang.
An experienced and trustworthy senior carpenter may be
promoted to a supervisor and may also be able to interpret
the engineer’s drawings and build under the supervision of
the director or engineer more complicated and larger
structures. He should identify and correct construction
problems such as deflection with or without the help of the
engineer or director.
The weight of a thatch layer is 35kg per m 2 , 60kg with
poles and with wind load 120kg per m 2 . The design of a
pole structure must include wind bracers and must be
strong enough to withstand strong winds such as
experienced, for instance, in the Cape Province. That is also
why nails cannot only be used and the knowledge of how
and where nuts and bolts must be used is very important.
TASA has committed to offering training seminars for
NHBRC inspectors, insurance companies, banks and
municipal building inspectors to inform them of
specification requirements and what to look at during
inspections.
Publications such as A Guide to Thatch Construction in
South Africa and Pros and Cons in the Thatching Industry can
be ordered from TASA.
For more information, visit: www.sa-thatchers.co.za.
www.timberiq.co.za