Proceedings e report - Firenze University Press

4. Causes of biodeterioration
WOOD SCIENCE FOR CONSERVATION OF CULTURAL HERITAGE
Over the last century, the basidiomycete wood-rotting fungi and beetle infestation have seen two
periods of high activity in Estonia. After World War Two when lots of buildings including those of
cultural value had to be renovated and repaired, the wood-destroying fungi easily spread all over
Estonia. Because of the substandard building materials applied, the timber used often had
inadequately high moisture content. The aftermath of this period lasted up until mid-1960s. The
beginning of another period of high fungal activity dates back to late 1980s and early 1990s and
occurred due to the gaps in the building code and lack of supervision. The second period mainly
affected private houses, cottages and auxiliary buildings and no extensive damage to the cultural
heritage was recognized. Research on wood-destroying fungi has established a clear-cut relationship
between the rate of wood deterioration and age of wood in the building. In many buildings the old
slightly damaged elements were and are replaced by new elements of the same size and shape whereby
the growth of destroying fungi is further enhanced as the spread rate in fresh cut timber is manifold
higher than in the old one.
Causes of fungal attack and beetle infestation in Estonia, Latvia and Lithuania differ from those in the
rest of EU countries. During the 50 years of Soviet rule the inadequate renovation and maintenance
system and low-quality performance in construction companies resulted in unreasonable and
technically inadequate changes in architectural heritage which account for the following causes of
fungal deterioration:
Changes in the moisture pattern of the ground floors, where due to the elevated road and surrounding
areas the vent pipes have been stopped up and this leads to the changes in the moisture pattern in the
ground floor and lower part of walls.
The floor structures changed during renovation, e.g. replacing the floor boards (damaged by fungal
attack) by concrete floors in turn resulted in changes to the moisture pattern in the lower part of walls
and indirectly affected all the building. Placing concrete floors in some parts of the building
deteriorated the performance of under-floor ventilation and the remaining wood flooring was easily
attacked by fungi. Besides, the timber floors were often replaced by low-quality flooring, which
accelerated the process of fungal decay.
Changes in the function of buildings and rooms, e.g. a church performing as a sports hall or chapels
and manor houses functioning as warehouses in agricultural production. These changes did not only
affect the moisture regime, they also involved extensive changes to the building structure itself, thus
leading to substantial changes to the exterior looks of the buildings of historic value.
Building damp rooms (shower-rooms, saunas, pools, etc.) in old-age buildings the initial design of
which did not feature these facilities. The damp rooms were insulated by various plastics that
substantially contributed to the deterioration of the surrounding timber elements.
Thermal insulation installed at historic buildings caused changes in the moisture and thermal regime of
the buildings resulting in condensation water that in its turn increased the moisture content of the
surrounding timber elements.
Inadequate performance of roof and rainwater runoff occurred as a rule due to the inadequate or
missing maintenance of buildings and resulted in the deterioration of the whole building and the
longer was the period of neglect, the more extensive was the damage incurred.
Summary
Humidity control is the best measure to prevent biodeterioration in buildings of cultural heritage and
requires the installation of temperature and humidity meters in all the buildings of architectural
heritage and places that house items of art heritage. The detected increase in humidity calls for an
effective analysis suggesting the measures to be taken.
Research on wood-destroying fungi has established a clear-cut relationship between the rate of wood
deterioration and age of wood in the building. In many buildings the old slightly damaged elements
were and are replaced by new elements of the same size and shape whereby the growth of destroying
fungi is further enhanced as the spread rate in fresh cut timber is manifold higher than in the old one.
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