Civil Engineering Reference
In-Depth Information
All types of timber, both softwood and hardwood, are used for this sort of
work, with very few exceptions. Products made of chipboard have no particular
demands as far as quality is concerned and can even be made from wood shav-
ings from demolition timber. The materials used for glue in parts of the produc-
tion process and the impregnation materials used in external timber cladding
come from questionable sources.
Timber is often a local resource, and all surface materials made of whole tim-
ber can be made locally. Timber is treated best at small mills. It is clear that it
needs human attention, and there are limits to how mechanized a sawmill
should be.
Durability is dependent upon the climate, the quality of the material and the
workmanship, but is generally good as long as the timber is not over-exposed to
damp. Artificially fertilized and quickly grown timber are undermining this
opinion, and could lead to the down-grading of timber as a building material.
Timber roofing is not suitable for damp coastal climates with a great deal of vari-
ation in temperature.
The primary energy consumption varies from product to product, but is gen-
erally low to moderate, with the exception of fibreboard.
There are generally no environmental problems relating to the production
processes at sawmills or joinery shops. Wood dust can, however, be carcinogenic;
this is particularly the case for oak and beech. The use of synthetic glue and
impregnation liquids can pollute the working environment as well as the imme-
diate natural environment, as effluent in either water or air.
Timber is generally favourable in the indoor climate, having good moisture-
regulating properties, but these are often eliminated by treatment with varnish
or vapour-proof paints. Untreated timber has good hygienic qualities. It proves
to have far less bacterial growth on its surface than the equivalent plastic surface.
Chipboard and veneer can emit gases from glues that have not set, mainly as
formaldehyde. Pine can release smaller amounts of formaldehyde which can
cause reactions in people who have very bad allergies.
Pressure-impregnated timber or timber treated with creosote should not be
used in greenhouses or on roofs, where the rainwater passing over the timber
runs into soil for cultivating food. Handling of creosote-impregnated materials
can cause eczema on the hands and feet even without direct contact. Bare skin
has to be protected. Creosote can also damage the eyes, and cause more serious
damage to health.
Technically, all sheeting and boarding can be re-used when fixed so that
removal is simple. Making all materials easy to dismantle would be a great
advantage, especially in interior use. Re-use of exterior timber boarding panels
or timber roofs would not be practical. These are surfaces that are exposed to all
the elements and get worn out over the years, so there would usually be no pur-
pose in re-using them.
