MONUMENTEN EN WATER Diest 2005 - WTA

applied on the walls and on this a plaster was applied. The aim of this intervention was to
keep the salt inside the masonry preventing them from reaching the plaster. Due to
detachment of the plaster layer, a new restoration was necessary. This took place in
1991-1994: at this occasion the plaster and the tar layer were removed and a new plaster
was applied. This new plaster is a ready-to-use restoration plaster for salt loaded substrates
and should not limit the transport of the salt solution from the substrate to the plaster. When
the monitoring started and the first investigations took place (July 2000), the plaster already
showed a serious decay that considerably increased in the following years.
3. Decay patterns
Fig. 1: The church submerged in sea-water during the flooding in 1953
The decay mainly affects the plaster covering the interior of the church. The stones
constituting the basement of the columns show only a white salt patina and little sanding.
The damage of the plaster is mainly located up to 4 meters from the ground level, and is
particularly serious on the walls (Figure 2) and the plastered columns of the choir. The
damage starts as peeling of the paint layer and formation of thin cracks and develops then to
sanding and crumbling of the plaster. This decay pattern seems to be typical of this plaster
when applied in very severe conditions and it has been observed on several occasions [2].
In some spots in the church the plaster layer is completely weathered and the brick substrate
starts decaying. Efflorescences are visible on the plaster and on the substrate when the
masonry dried out during low RH periods.
Fig. 2: South wall of the choir showing serious damage
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