to diagnose dampness - Free Technical Help - 01626 872886 .
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damp symptoms for yourself - look for these clues in the photographs
1. Can you see the original
damp proof course?
Yes = it looks like
a dark line and if I scrape it looks like slate or bitumen/felt. (It
is most likely to be just under the air brick, if you have a timber
floor, as part of the original protection of the floor joists)
No = there may not
be one, or, more likely it has been covered over with soil, steps, pathways,
roadways or other building alterations. This is called 'bridging' the
damp proof course and will give you all the symptoms of rising damp.
Wet Walls showing green surface
growth - Verdigris.
2. Is the damp proof course
line that you can see about 6" (150mm) or more above the outside
Yes = good, that is
correct. This drop from the DPC to the ground is to protect against
splash-up by falling rain. Check that the gutters and downpipes are
in good condition and go outside in pouring rain to check that they
can cope in a downpour.
No = bad. You will
either need to lower the ground level or insert a new DPC at the correct
height and 'tank' the walls below that new level.
Surface salting also visible
3. Can you see
fluffy white 'salts' on the wall inside, maybe pushing off the paint or
Yes = you have rainwater
splash up or gutters overflowing. Or, under a window frame, you may
not have a clean 'drip' slot. Check the exterior walls for defects,
check gutters and downpipes, check the pointing in the joints, treat
with Ultra Proof waterproofer.
No = your dampness
may be due to 'hygroscopic salts' deposited in the wall from chimney
deposits (after burning coal or wood), or from a previous use of the
building (e.g. Coal shed, animal food store, butchers shop). Treat with
Salt Neutraliser and replaster to our 'tanking' specification using
BondAcryl. In severe cases it is best to use the Mesh Membrane wall
lining system, rather than 'tank' or replaster - chimney salts can burn
back through even the best render backing coats sometimes.
Green 'verdigris' caused
by rain water splash up.
Salting in brickwork above
4. Do you have a cavity
wall or a solid wall?
Yes = because you
see only bricks laid along their length - no brick ends visible at any
level. This type of wall should resist water penetration, because of
the air gap. If it is showing damp symptoms on the inside the cavity
may be blocked or the wall ties may be dirty.
No = this wall is
of solid construction. You can see rows of brick 'stretchers' and then
mixed rows of 'headers' and 'stretchers'. Penetrating damp or splash
up rainwater can go straight through.
5. Have you got a timber
Yes = look for the
air bricks. Even if they are present the floor itself may have rotted
and been replaced in concrete, 'bridging' the DPC and often causing
rot in the skirting boards.
No = no air bricks,
all concreted. Check you do not have partial solid floors, with sections
of timber flooring cut off from an air supply - they will rot.
Internal view - peeling wallpaper
and wet skirting boards, resulting in typical Dry rot cubing and convexity.
you see a water source - on the outside walls
A. Green stuff on the
wall - look up - are the gutters and downpipes OK in a really heavy
B. White stuff on the
wall - it indicates dampness - check window cill 'drips', roof tiles
and slates, flashings and abutting structures (even stored goods against
C. Neighbours garden,
road, path or garden higher than yours - water flows downhill!
D. Water leak from underground
- is an area of garden or path strangely green at the height of a Summer
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5. Have you still got a
Yes = find the air
bricks. Even if they are present the floor itself may have rotted due
to blockage or shortage of air flow. Fit new bricks to the current standard.
No = the old air bricks
are still there on the outside but it is filled with concrete inside.
Take them out and make good with bricks and mortar, unless they are
acting as cavity wall vents or provide ventilation, via a pipe, to a
remote timbered area.
Want to become Qualified
in Dampness and Timber Decay?
Contact us for details of
Call David or Angela on:
We are long term members
of the PCA - The Property Care Association - the professional body
for the Damp Proofing industry and our Dampness Surveyors have over
50 years of experience between them.
If you prefer to use a
Contractor, rather than our free advice service, then go to the PCA
Website where you can find the nearest qualified specialist companies.
They should give you the same information that we provide. If in doubt
E Mail their Reports to us for checking, before spending any money.
Link for the PCA - click
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Site written by: David
David Moore, B.A. (Hons.),
C.T.I.S., C.R.D.S. Technical Author
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