Civil Engineering Reference
In-Depth Information
The log building technique is the most widespread technique of the heavy struc-
tures. This method uses a lot of timber and is statically based on the compressive
strength of timber.
The Norwegian Building Research Institute has recently completed a research
project on the environmental efficiency of different types of building, from the
construction phase through a 50-year life span. As far as resource consequences
and pollution effects are concerned, the log building technique came out best,
despite the intensive use of timber. As the time span was only 50 years the pos-
sibilities of recycling the building materials was not taken into account,
although this is an integral part of this technique, as is the high durability of
such a structure. Log houses of more than 1000 years old exist in both Japan and
Russia.
Types of structural walls
Log construction
In this method, logs are stacked directly over each other and notched together in the cor-
ners. These buildings are usually rectangular, but can have up to 10 sides. (A 10-sided
log built barn exists at Fiskberg in Burträsk, Sweden.)
A solid timber wall has good acoustic properties and fire resistance. The thermal
insulation is also good. For 700 to 800 years it has been considered the warmest alter-
native.
Pine has been the timber most used in log construction. It has been left open and
exposed to all weathers, so it has been well tested for hardiness. In log construction with
external panelling, spruce can also used. Larch makes a solid and durable log building
and is very much in use in Russia. For outhouses birch, aspen and lime can be used. Lime
is a large tree, common in the Carpathians (in the eastern part of Romania, where it is
used for the log construction of dwellings. In particularly damp areas, exceptionally
durable timber such as oak must be used for the bottom plate.
There are many ways of forming the logs and their joints, depending upon which tim-
ber is used (see Figure 13.38). Pine should have its surface worked by profiling, while
spruce needs only the removal of the bark to keep its strength. Accessible technology
and rationality have played a crucial role in the development of techniques. Type (a) in
Fig. 13.38 belongs to the nineteenth century style of building and was well suited to the
new machinery of the period - sawmills. The disadvantage was that it was difficult to
make them airtight, and they were not as strong a joint as hand-worked logs. Types (b)
and (c) from Finland and Canada come reports that the log-built house is on its way back,
and in Canada and the USA between 50 000 and 60 000 log dwellings are built every
year.
Vertical load-bearing panelling
This was developed in order to place a solid timber wall in a house without having to
wait for settling, unlike log construction. The timber shrinkage along its length is mini-
mal. Outer walls can then be panelled directly and windows installed (see Figure
13.39).
