Civil Engineering Reference
In-Depth Information
split into quarters. The pieces are often boiled to reduce the
chance of cracking when being cleft, but heating to over
70°C also makes the resin melts out, and impregnating
effect is lost.
Cleaving is performed using a special knife which is
35 cm long and has a handle on each end. The sharp
blade is usually placed radially on the end of the log and
knocked in. As long as the blade is kept at right angles
to the rings, it is possible to cut in at the side of the log.
Rainwater is later taken off the roof in the perfectly
formed annual rings. The shakes should be about
2-3 cm thick. It is also possible to cleave the shake with
machine.
The shakes are put on battens using the feather board-
ing principle with 2-3 mm between them to allow for shrink-
age and expansion. A normal covering consists of two or
three layers. They are nailed with wire staples so that the
holes are covered by the next layer. Usually one staple per
shake is enough. The staple should not be so long that it
penetrates both the battening and the roofing felt. The lay-
ing details are shown in Figure 15.20. The shakes can be shaped in many different ways,
the most complex being reserved for ecclesiastical buildings.
Archaeological discoveries show that shake roofs have existed since the early Bronze
Age. Around 230 BC the majority of roofs in Rome were covered in shakes.
Figure 15.18: A Sutak roof.
Source: Eriksen
Shingles
Shingles are sawn by a circular saw. They are 40 cm long and 10-12 cm wide with a thickness
of 1 cm at the lower end and 0.5 cm at the upper end.
They are laid next to each other with a spacing of about
2 mm, usually in three layers, which means that the dis-
tance between the battens is about 13 cm. In the nine-
teenth century the majority of buildings in New York
were roofed with shingles.
Timber cladding
Timber panelling has a long tradition as a
cladding material, first as external wall pan-
elling and later as internal wall and ceiling
cladding. The different types of cladding have
changed slightly in recent years, particularly to
suit mechanical production. Special forms of
panelling include cladding of shingles and
shakes. Cladding with twigs and branches also
has a long tradition in certain countries. Juniper
Figure 15.19: System for cleaving shakes by hand
for softwood. Oak shakes are always cleft radially
in the wood. Source: Vreim 1941
