EWJ June 2024 web - Journal - Page 98
Interstitial condensation is more dangerous to properties as it often occurs in areas that are not visible. As
it continues, the damp and mould created can damage the structure of the property, often quite seriously,
before the existence of the damp becomes obvious.
Buildings that have been retrofitted to improve their
energy efficiency without taking into account that the
building needs to “breath” can increase the risk of
damp, especially condensation. With increased requirements to make buildings more energy efficient,
ensuring this is done in a way that does not increase
the risk of damp and mould developing in the buildings is becoming ever more important.
Rising damp
Rising damp occurs when moisture rises from the
ground through a wall or floor. This is a natural occurrence that is usually stopped by a damp-proof
course or membrane. Because the moisture that
causes this kind of damp comes from the ground, it
only occurs on the ground floor of buildings and is
most easily recognised by “tidemarks” appearing on
the walls. These tidemarks appear once gravity or
evaporation have stopped the moisture rising any
higher up the wall, normally at about 1m above floor
level.
Here are some examples of what damp may look like.
Older properties that do not have a damp-proof
course are more likely to experience cases of rising
damp than more modern properties. However, if the
damp-proof course has been damaged in some way
modern properties will also see this kind of damp
appearing.
In addition, changes made to the ground outside the
property, for example through raised garden beds of
the addition of a new drive, could also affect effectiveness of the damp-roof course, or even block ventilation
bricks, increasing the risk of rising damp.
Damp in a ceiling corner - Anderson Wilde & Harris expert building surveyors
Penetrating damp
Penetrating damp is caused when moisture seeps into
the property through ceilings, floors and walls, and is
normally related to structural issues. There are numerous causes of penetrating damp, but some examples include things such as damaged roofing tiles or
felt, faulty guttering, burst pipes and other plumbing
issues, and cracks in walls or brickwork.
Penetrating damp will often make itself visible through
damage to plastering, decaying timber or watermarks
on masonry. However, as with interstitial condensation, the existence of penetrating damp may not always be immediately visible, especially if it is occurring
in areas that are not accessed or inspected on a
regular basis.
Damp behind a radiator underneath a window - Anderson
Wilde & Harris - expert building surveyors
Finding the cause
As you will see from the above, identifying the cause of
damp within a property will depend greatly on which
type of damp is occurring. In some instances, the likely
cause will be easier to identify and resolve, while others, such as penetrating damp or interstitial condensation, are more complex, often requiring more
comprehensive investigation.
Consider an example of penetrating damp caused by
a leak in a roof. Water entering the property from a
damaged roof will seek the path of least resistance as
it trickles into attic or roof spaces, often traveling along
beams or insulation material. This can cause damp
patches on ceilings to appear far from the source of
the leak. Restricted access or areas covered by insulation material can make finding the source even more
difficult.
EXPERT WITNESS JOURNAL
Damp surrounding a window frame and damaged ceiling Anderson Wilde & Harris - expert building surveyors
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JUNE 2024