Civil Engineering Reference
In-Depth Information
fine distinctions were not drawn, and
creosote and tar were used whenever
the occasion demanded. Although
there are many survivors from these
times, there must also have been
many examples of non-durable
species which have not survived.
Western red cedar is popularly
used for cladding. It is a naturally
durable species and, in the past, not
usually treated as it is resistant to
treatment. Run-off may stain
surrounding materials, and it is
therefore usually fastened by secret
nailing. It eventually weathers to
shades of grey if left untreated. For
the durability of other species, see
BRE Digest 407 (Figure 9.29).
Untreated timber may be subject to
biological growths as well as risk of
decay. The safe use of surface
biocides is discussed in BRE
Digest 418
(75)
.
PVC-U degrades slowly on
exposure to the weather, largely
under the influence of UV radiation.
Sidings of PVC-U are prone to colour
changes or to 'bloom' - both have
been observed in BRE site
investigations.
Figure 9.29
Vertical cladding with batten joints on a west facing exposed location. The timber is
probably larch, and although possibly creosoted some 40 years earlier, has had no
attention since. Some rust staining from the nails is in evidence
Work on site
Inspection
The problems to look for are:
◊
impact damage
◊
rot in timber boards or battens
◊
deterioration of surface finishes
Maintenance
For maintenance of timber finishes,
see the next chapter.
◊
delamination of plywoods
◊
warping of boards
