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Efflorescence, Masonry Surface Salt Deposits |
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The source of true rising damp is ground moisture climbing up through the internal pores and capillaries of the masonry carrying damaging
ground salts in solution, (sulphates, nitrates chlorides, etc.,). Moisture finds its own level along and through the masonry. As the masonry
slowly becomes saturated the moisture level rises with the lower masonry always being the wettest. Only when the masonry has been fully
saturated does the moisture rise and at this point the masonry will be equally wet on both sides of a solid wall or both leaves of cavity
brickwork sharing a common damp-course. As the moisture evaporates from the surface a “hairy looking” crystalline surface salt deposit
appears on the exposed surface.
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“Rising damp” requires support from sufficient soil moisture content and natural active water table content.
Active “rising damp” will not occur during extended periods of severe drought and in many cases months of above average rainfall is required
to bring up the water tables and soil moisture contents to induce and support rising damp.
“Rising Damp” has no associated musty smell and is a natural deterrent against
mould growth. Consider the medicinal properties and use of
saline solutions for treating open wounds or as a mouthwash. High salt content and visible surface presence on brick masonry, stone, plaster
and mortar disintegration are true indicators of “salt” contamination and if not visibly present the experienced investigator should perform
a salt detection test.
During periods of high humidity , cold damp winters, these hygroscopic salts may absorb rain water or air-borne water
vapour, dissolve, and be re-absorbed into the masonry to seemingly disappear but to return again as the wall dries out.
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Sub Florescence
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Sub-florescence is the potentially harmful accumulation of soluble salt crystals deposited under or just beneath the masonry surface as moisture
in the wall evaporates from the surface. Constant masonry moisture content is rarely a problem where the masonry extends below ground level,
however, where the masonry is above grade the wetting/drying cycle causes an expansion/contraction cycle of the contained salts which if sufficient,
may induces fretting and disintegration of the masonry, (clay brick and/or natural stone), and mortar.
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