Single Leaf Wall problems
to check and eliminate before replastering or lining with an Air Gap
thermometer and a 'damp meter' (see www.dampness-info.co.uk/meters.htm)
are useful tools for this diagnosis - if not available use the back
of your hand to assess the relative warmth of one affected area to another
dampness, due to poor 'pointing' (mortar in the joints between bricks
or blocks), crumbling or cracked brick faces (spalling) or cracked or
hollow render. Dampness that comes through the wall may bring 'salts'
to the surface of the plaster and these 'salts' attract more moisture
from the air.
- rake out the joints and re-point with a soft mortar mix (6:1:1
- sand/cement/lime) with a plasticiser additive in the mix (Renderproof)
or hack off and re-render, again with a soft mix, but using BondAcryl
to bond the new render to the wall and the edges of the old render.
Scratch well between coats and damp the wall well before and after rendering,
to slow the drying process (reduces the risk of cracking).
with penetrating damp and how to eliminate it call our experts on 01626
this forms on the coldest surfaces in a room and often grows 'black
- hack off all the plaster and fit an Air Gap Membrane, plus insulation
with mould and how to eliminate it call our experts on 01626 331351.
of the damp proof course
'bridged' or covered by high ground, pathway, garden or abutting new
structure, (e.g. conservatory, steps): the damp proof course must be
a minimum of 6 inches (150mm) above outside ground level, in order to
avoid rainwater splash up causing penetrating dampness.
- remove the obstruction or inject a new damp proof course at the
proper level (see Damp Proof Injection)
with 'bridging' problems and how to eliminate them call our experts
on 01626 331351.
pipe or wire penetrates the wall: pipes, wires, bolts and other fixtures
that pass into the wall can carry moisture inside, which may emerge
at that level or drip down and show elsewhere.
- remove the obstruction, or carefully seal the entry point. Pipes
and wires should always be routed to climb up the wall immediately before
entering the duct or hole, to avoid channeling the water by gravity.
with services leaks and how to eliminate them call our experts on 01626
Pipe Leaks inside the walls
concealed inside the wall: usually heating or mains water, but can also
be boxed in foul water pipes or cistern overflows in modified houses.
- remove the boxing or a brick or block from the wall to expose the
with water leaks and how to eliminate them call our experts on 01626
What do the symptoms
- white, fluffy salts, plaster possibly 'blowing' off the wall - 'efflorescence'
- you have a water source which needs to be found and eliminated. Use
our Water Leak Checklist (click here).
- Salt Neutraliser might work if you can find and stop the leak,
or the plaster may be too damaged and need replacement to our Specification.
Either replaster to our Renderproof Specification or line the walls
with our Mesh Membrane - both act as barriers to the passage of damp
and salts, but the Mesh Membrane also provides insulation and is foolproof.
with 'salts' and how to eliminate them call our experts on 01626 331351.
Close up of fluffy white
salts on a chimney breast.
- damp patches on the ground floor - at low level, right down to the
skirting board - that come and go - you have 'hygroscopic' salts that
are attracting moisture from the air.
- you may have Rising Dampness, or your damp proof course may be 'bridged'
by high outside ground, plaster on the inside or debris in the cavity
(cavity walls only). Rectify any defects and if necessary inject Quick
Cream at the correct level to form a new Damp Proof Course. The
plaster will need replacement to our Specification.
and how to eliminate them call our experts on 01626 331351.
Peeling wallpaper on hygroscopic
- damp patches on or around chimney breasts - sometimes showing yellow
or brown stains in wallpaper or paint - you have 'hygroscopic' chimney
salts that are attracting moisture from the air, which may include tars
and other chemicals from burning wood or coal.
- these 'salts' are very difficult to hold back in the wall, even with
the replastering to our Specification carried out to perfection. We
recommend using Mesh Membrane - a
type of dry lining - to allow you to replaster using normal, lightweight
plaster, with no risk of further 'salting'.
and staining and how to eliminate them call our experts on 01626 331351.
Patches of both hygroscopic
and penetrating damp.
Neutraliser - a
clear liquid used to neutralise 'salts' in render, plaster or masonry,
either to attempt to save otherwise sound plaster or as a preparation
prior to re-plastering to our Specification. Apply two coats, wetting
in between with fresh water.
a blue concentrated additive for sand and cement, designed to be dissolved
in water. It waterproofs the render mix and acts as a plasticiser and
here for the Replastering Specification Data Sheet
easy to install dimpled plastic 'air gap' dry lining membrane, supplied
in rolls like wallpaper. Designed to cover damp or salty walls and provide
a fresh surface for replastering with a modern lightweight plaster (usually
straight to our Shop
Learn from the UK's top
Expert: become your own expert - save money.
DIY Master Class in Dampness and Condensation - become your own
Expert in 1 hour! Buy our "Dampness in Buildings" reprinted
book by the great expert Graham Coleman. A great read, short and to
here to buy the reprint.
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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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