As damp disappears, walls can show indicators that must
be carefully observed.
Firstly, changes will occur according to the amount of rising
damp existing inside the masonry; secondly, to the surface
condition: for instance, no indicators will show if plaster is
completely covering and insulating.
Also, sometimes no changes can be seen from a wet wall to
a dry wall if salt-contaminated plaster has not been restored.
Smell indicator:
• The unpleasant odour of mould diminishes or
disappears completely.
Touch indicators:
• mineral paints easily crumble to touch;
• fine plaster flakes easily to touch;
• plaster may sound hollow.
Visual indicators:
• partial or total fading (it depends on the amount of
salts present on the surface of the wall: the lower the
amount of salts the more the fading);
• formation of moisture stains caused by salt migration
(for instance, by the increase in concentration of salts
in plaster, especially in the evaporation zone);
• increased salting, especially during evaporation;
• mineral paints (e.g. lime-based paints) flake off the
plaster, especially in evaporation zones;
• organic paints cause blisters in the evaporation zone;
• cracks occur in the plaster due to the pressure caused
by salt crystallisation;
• moulds existing in the lower portion of the wall become
clearer (from black to greyish)
• upholstery may feel more humid due to the concentration
of salts especially in the evaporation zone (deposit of
salt nests and consequent hygroscopic moisture) and
the increased airborne moisture may easily generate
moisture stains.
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DEHUMIDIFICATION INDICATORS IN MASONRY