Testing
1. Press the meters pins lightly on the surface
of the walls and note readings. Take readings
in damp affected areas every 100mm (4”) up
and across the wall to establish the extent of
the problem.
2. In the areas of highest readings try to push
the pins further into the wall. Are these
readings higher, is the plaster soft or hard or
too hard to penetrate?
3. Take readings from an unaffected area in the
same room to see how much of the reading
is ‘normal’ for that building at that time of
year. A steady, low background reading in an
old building does not necessarily indicate a
problem.
Analysis
1. Rising dampness is generally indicated by
readings which start in the skirting board and
continue to between 150mm (6”) and 500mm
(20 “) up the wall, with a sharp cut off, from
high reading (say 2%) to zero over the space
of 50mm (2”) or less.
2. Penetrating dampness can occur at any
height from the ground, look for external
defects and high readings around the defect,
gradually declining away from the affected
area. Typically caused by poor mortar joints
(‘pointing’), leaking gutters, blocked drains,
downpipes or overflow pipes, pipes or wires
penetrating the wall, plants or creepers
attached to the wall, gate posts, abutting
garden walls and faulty hollow render.
3. Condensation is usually indicated by mould,
generally black or green in colour with low
meter readings spread evenly across the
wall.
4. Cold spots can give rings or patches of
mould, these are often caused by isolated
small outside defects in solid walls or by
dirty wall ties or gaps in cavity insulation in
cavity walls.
5. Chimney breast staining, sometimes
spread into adjacent alcoves, is caused by
‘salts’, resins and chemicals being slowly
washed through the walls as the result
of moisture in the chimney. The moisture
can come from open pots, poor flashings,
poor chimney stack pointing, leaking back
boilers or condensation. Condensation
in chimney voids can be caused by lack
of ventilation in the flues, breasts or in
covered pots.
How to Take Readings
WALLS
How to test for damp guide
2