6 Wood Discoloration

8.5 Damage to Structural Timber Indoors 207
for the production of “myco-wood” for pencils, rulers, etc. (Luthardt 1963);
test fungus in EN 113 for hardwood samples.
8.5
Damage to Structural Timber Indoors
8.5.1
General and Identification
The indoor wood decay fungi (“house-rot fungi”) cause considerable economical
damage in buildings. They may be considered to be the most important
“wood fungi” as they deteriorate wood at the end of the economical series
“forestry” – “timber harvest” – “storage” – “structural timber” – “indoor use”.
For Britain, it has been estimated that the cost of repairing fungal damage of
timber in construction in 1977 amounted to £ 3 million per week (Rayner and
Boddy 1988). An estimate for the former East Germany amounts to an avoidable
damage in old houses of e1.5 billion (Huckfeldt 2003). In the northern
hemisphere, mainly coniferous wood is used as interior structural timber, in
Germany particularly Picea abies. The most important wood-degrading fungi
within buildings in Europe and North America are therefore fungi that cause
brown rot in conifers. White-rot fungi, which preferentially attack hardwoods,
are less common in buildings. Depending on the state of knowledge, formerly
often only three more well-known species (groups) were called house-rot
fungiinEurope:theTruedryrotfungus,Serpula lacrymans, the cellar fungi
Coniophora spp. (formerly only C. puteana) and the indoor polypores, formerly
called “Poria group” (probably mainly Antrodia vaillantii). These three
groups cause about 80% of the fungal wood damages in buildings. Recently,
the Oak polypore, Donkioporia expansa, has also been accepted as important
indoor rot fungus (Kleist and Seehann 1999). The Gill polypores (Falck
1909) may be included to the indoor species as they are common destroyer of
painted coniferous window timber (Fig. 8.17) and also occur on damp roofing
timber.
There are some evaluations on the frequencies of the various species involved
in indoor wood decay. A survey of 1,500 buildings in New York State
from 1947 to 1951 showed several fungi and Hyphodontia spathulata, G. sepiarium,
A. xantha, andG. trabeum as most frequent isolations from decayed
wood (Silverborg 1953). An investigation of 3,050 buildings in Poland showed
53.8% S. lacrymans, 22.4% C. puteana and 11.3% A. vaillantii (Wa˙zny and
Czajnik 1963). A survey of 1,200 biotic damages in buildings of the former
East Germany over 21 years resulted in 34.8% S. lacrymans, 14.6% Coniophora
spp., 13% soft rot and 8.7% “Poria” (Schultze-Dewitz 1985). An evaluation of
749 damages in Belgium between 1985 and 1991 revealed 59.4% S. lacrymans,
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