6 Wood Discoloration

148 7 Wood Rot
Table 7.5. Hazard classes of timber, conditions for wood use, resistant wood species, and
chemical preservation measure
Hazard condition for wood use durable wood minimum
class preservative measure
0 indoors, if
wood moisture ≤ 12%,
timber open at 3 sides or
coating against insects
none
1 indoors colored heartwoods prevention of insects
air humidity ≤ 70%, sapwood proportion < 10%
wood moisture < 20%
2 indoors: colored heartwoods prevention of
air humidity > 70% of durability class fungi and insects
in wet areas: 1, 2 or 3
water-repellent coating
outdoors: without
weathering
3 outdoors: weathered colored heartwoods prevention of
without permanent of durability class fungi and insects,
ground or water contact 1 and 2 weatherproof
indoors: wet rooms
4 permanent ground colored heartwoods prevention of
or fresh water contact, of durability class 1 fungi and insects,
special prerequisites weatherproof,
for cooling towers and prevention of
marine timber soft-rot fungi
There is still a worldwide spread superstition that wood properties like
resistance against fungi depend on the moon. The wood of trees felled at
a certain date related to the moon phase is thought not to swell nor shrink,
to be incombustible, resistant to fungi and insects, and to become very hard.
Those oscillating changes of the properties of the woody tissue, which mainly
consists of dead fiber or tracheid cell walls, are biologically impossible. Thus,
all specifications are in contradiction to scientifically based results (Wa˙zny and
Krajewski 1984; Seeling 2000; bamboo: Yamamoto et al. 2005). The positive
effects of a certain felling date observed in the practice may be due to other
influences: People which believe in lunar influences select in the forest wellgrown
trees, use appropriate drying, storage methods and wood design, that
is, the wood, its processing and use are of high quality and thus the wood is
more resistant to deterioration.
There are several standards to determine the resistance of untreated wood
and wood-based composites against fungi and also to test the efficacy of
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