What is rising
causes natural rising damp?
It is a strange part of our
physical world - the way water climbs up through capillaries - the fine
tubes inside building materials.
Remember, there are many
other causes of damp, salt or discoloration, so check those first -
see our Project Page - Damp: Diagnosing and Analysing.
Any masonry structure, unprotected
by a properly installed damp proof course, is susceptible to both natural
and man made rising damp. Moisture will rise by capillary action (a
suction phenomenon arising at the boundary between moisture and a small
tube, crack or other tiny, enclosed passageway known as a capillary)
through the pores of the masonry, seeking a means of evaporation. The
moisture will continue to rise until it reaches a height where, unless
no evaporation is possible, gravity takes over and pulls it down again.
This height is seldom more than 1.20m, although deposits of 'salts'
may be found higher in the wall, often driven there by the use of non-breathing
plasters, renders, 'tanking', paints or vinyl wall papers.
with finding out what is causing your damp call our experts on 01626
Damp proofing at ground level
is the provision of a barrier across the whole width and length of a
wall, which cuts off the capillary supply of moisture naturally rising
from the ground. In external walls, to avoid rain water splashing up
above the damp proof course, the DPC (damp proof course) has to be positioned
at least 6 inches (150mm) above the outside ground (Building Regulations
and British Standard 6576).
with damp proofing Regulation call our experts on 01626 331351.
What types of
barrier can be used?
Historically, a variety of
materials have been installed during the building process - stone, slate,
lead, zinc and stainless steel and more recently (and currently) plastic.
However, once a building
has been erected it is more difficult to insert a physical DPC (although
stainless steel sheet can be vibrated into walls, via saw cut slots),
so other methods have been developed for remedial action;
1. Water repellent - liquid,
paste, gel, or cream by injection - amateur and professional
2. Pore blocking - cement
based mortar, by injection - mainly professional
3. Osmotic - passive or active,
via embedded wires - mainly professional
with types of damp proof course call our experts on 01626 331351.
How these are
1. Water repellent
- holes, usually between 10-12mm in diameter, are drilled either into
the mortar joints or via the bricks or stones and the chemical is injected
using a high pressure pump (liquids) or low pressure hand pump or skeleton
gun (creams, pastes and gels). The chemicals spread through the damp
masonry, over a period of several months, to join up and form a continuous
water repellent layer. This is NOT a solid vapour barrier - it prevents
further liquid water from passing through, thus allowing the wall to
2. Pore blocking -
the cement based injection mortar is mixed with water to form a 'slurry'
and injected from a re-usable, plastic bodied, heavy duty 'gun'. It
rapidly sets, giving off great heat, to form a solid plug in the wall.
The holes are generally 18-20mm in diameter and this method is only
really suitable for thick, stable stone walls. The injected mortar then
slowly generates impermeable 'salts', which over several months block
the pores in the wall and prevent moisture from rising. This method
requires large drilling machines, expensive drill bits and mortar guns,
making it uneconomic for amateur use.
3. Osmotic - the old,
'passive' system used copper wires, which unfortunately corroded, but
the latest Lectros Active System utilises a titanium wire, connected
to a special mains powered control box, which is run around the walls
rather like a ring main. Bent at regular intervals to form anodes, the
wire loops are inserted into large holes drilled into the wall (internally,
externally or both if necessary). The wire is hidden in formed "chases"
or existing, raked out brickwork joints and the whole system is earthed.
The electricity from the mains supply passes through a transformer,
through the anodes and to earth, setting up an electrical field, which
repels the damp. The holes are filled with a special mortar, to ensure
good conductivity. This method requires large drilling machines, expensive
drill bits and special mortars, making it uneconomic for amateur use.
with methods of damp proofing call our experts on 01626 331351.
What if my walls
are not brick?
It does not matter - you
can still use DPC Cream.
The modern injection cream
products perform well in all types of wall and unlike the older liquid
injection methods the slow release of a uniform amount of cream per
hole ensures good spread between holes and a reliable result.
with damp, thick stone walls call our experts on 01626 331351.
Not at all.
Installation using DPC cream
based products is neat and very quick. A series of small holes (10-12mm
diameter) are drilled at least 6 inches (150mm) above ground level (exterior
walls), the chemical is injected, the holes filled and the result almost
invisible. In some cases, the plaster can even stay on the wall, if
it can be seen to be sound. It must be remembered however, that rising
damp will probably have brought water soluble salts into the plasterwork
and these hygroscopic salts will still attract moisture from the atmosphere,
even after the wall itself has dried out. Care must be taken to minimise
the effect of the residual salts. Sometimes Salt Neutraliser liquid
can deal with minor patches of 'salt', if the plaster is otherwise solid.
with installation of a damp proof course call our experts on 01626 331351.
For more technical information,
product costings or the name of your nearest qualified Contractor go to
Property Repair Systems - call us on 01626 331351.
from the UK's greatest 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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