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Rising Damp / Salt Damp |
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“Rising damp” is very widely misdiagnosed in existing buildings, based on the incorrect interpretation of visual
evidence and the readings of moisture meters. Over the last 25 years many
“specialist” remedial contractors have misdiagnosed “rising damp” resulting in not only a waste of the clients'
money and resources; but unnecessary damage to original plasters and finishes. That money might have been spent on more cost-effective
maintenance and/or repair works. Whilst the installation of remedial damp-proof courses is often very necessary
if properly installed they may be ineffective if wrongly specified.
“Rising damp” occurs at the bases of walls where the dampness is always higher minimising in concentration further
yup the wall. Water accumulating there has a tendency to "wick up" through the capillaries that are present in the walls, be they
brick, block, most sedimentary natural stones; and through the mortar in which they are laid. Damp-proof courses are there to block
this upward movement of moisture but sometimes are ineffective through incorrect diagnosis.
Rising damp is even rarer during hot summer weather and severe drought conditions when water table levels have dropped
significantly. Soil moisture content must exceed ambient levels to provide for an excess of moisture to support active capillary rise.
An effective visual indicator is the condition of the drilled masonry debris during installation which would appear either damp, or
dry and dusty. Observe the installation and assess the dampness of the drilled masonry dust?
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The Building Code of Australia, to which all new construction must comply, requires damp-proof courses, (dpcs), to be placed
through the full thickness of the base of walls below floor level to form an impervious layer that keeps rising dampness out
of the interior of the structure. (SAA Masonry Code, AS3700.)
Where there is a continuous supply of water rising up a wall, it will contain dissolved hygroscopic ground salts, (which create a saline solution),
and when that water dries out at the surface the salts will crystallise. If the crystals form on the surface of the wall as a white furry
coating, it will be suffering from non-damaging efflorescence, but
if the crystallisation occurs within the bricks or mortar, the forming crystals can exert pressure that causes the surface to break down and
fret away, ( sub-florescence ). In most of Australia this phenomenon is
called salt attack, but the South Australian name for it, salt damp, is often heard. With rising damp, being supported by a
continuous supply of water salt attack damage worsens over time.
Saline solutions, having strong bactericidal properties, are regularly used by doctors and medical staff to cleanse open wounds and rinse open
surgery procedures. “Brine” is commonly used in the meat industry to preserve meat during storage. Rising damp, (salt damp),
kills mould spores and inhibits mould growth.
RISING DAMP = SURFACE EFFLORESCENCE
NO EFFLORESCENCE = NO RISING DAMP
RISING DAMP KILLS MOULD
SURFACE MOULD PRESENT = NO RISING DAMP
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