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Damp problems can be allocated into three categories: Rising Damp,
Penetrating Damp and Falling Damp. Here we discuss the definition
of these, how they occur and how it can be resolved.
Rising Damp
Rising damp is the presence of moisture, specifically at ground level,
internally within the structure of a property. If your property is suffering
from rising damp you will see damp patches on plaster work, on your internal
walls, at the ground floor level. Further indications of rising damp are:
rotting skirting boards and low level mould on wallpaper.
In buildings and houses, to avoid rising damp, there are two requirements:
The first is to make sure the ground level outside is lower than the floor
boards internally at ground level (and lower than the damp proof course if
one is present). If the external ground level is higher, there remains
no protection from surface water, leaving it to penetrate the walls.
This type of rising damp can be rectified, by installing a drainage gully,
which will take this surface water away from the affected area which in turn
will solve the damp issue.
The second requirement is to ensure a damp proof course (DPC) is installed
and intact. A damp proof course is a protective barrier, installed above
the external ground level, but below the internal ground level, in effect
separating the two. This barrier is waterproof, therefore any damp from
surface water, only rises to this level, leaving your internal walls damp free.
Therefore the second reason for rising damp is the breach of this damp proof
course.
Rising damp of this type can be rectified by a damp proof course
injection. Usually this is performed by drilling 10mm holes in the brick
at the affected area where the damp proof course has failed. A special solution
is then injected into these holes, which absorb into the brick. This solution
changes the properties of the brick injected, so the brick becomes the
waterproof barrier, as it no longer allows water to pass through it, in effect
creating a damp proof course with the brick itself!
Penetrating Damp
Penetrating damp is where moisture travels through the wall structure,
usually through cracks or poorly pointed window frames. Very often we see
the exterior finish of a building in a poor state of repair with internal
damp problems. Generally people are unaware of the potential problems caused
by even the smallest of breaches in external structures of houses and buildings.
A small crack in a wall render can cause significant damp problems, even though
the problem only looks minor externally.
The first thing to repair is the cracks to the external structure, in this case,
the render, making sure the correct types of materials are used in this wall repair.
This would usually be followed for example, with a suitable high quality coating or
render system, which would be dependent upon the building’s circumstance.
Falling Damp
Falling damp is when the roof structure of a house or building has deteriorated
and water is left to penetrate the walls from the top down. General signs for
detecting falling damp are similar to rising damp, damp walls, peeling wall paper
and mould, but obviously this would appear in the upper section of a building
(or upstairs in a house) and would be noticed around window lintels and ceiling
area internally of an external wall.
Unfortunately Avant Coatings Ltd cannot help with falling damp as we do not
perform roof repairs. If you suspect your house or building is suffering from
falling damp, you should contact a competent professional roofing company.
Damp In Old Buildings
In older buildings usually constructed with solid walls and lime mortar, much
thought needs to be given to damp, condensation and moisture levels within the
building. In days gone by these old buildings had open fires and drafty wooden
windows and doors. When the fire was lit, it drew air up the chimney, which took
the moisture with it causing a high level of air exchange within the building.
In more modern times the old open fires have been blocked up in place for modern
gas or electric fires, with the addition of central heating systems. The old drafty
windows have generally been replaced with PVC sealed units. Following the improvement
in these areas, the air in buildings is now effectively trapped and does not exchange
at the rate it traditionally did. On top of this low air exchange, modern living
produces much higher levels of moisture, with tumble dryers, cooking, showers and
baths all creating very high levels of moisture. Once the internal moisture levels
become so high, it is no wonder it becomes evident within the structure and fabric of
old buildings.
Very often the best remedy for damp in old buildings is ventilation.
Old buildings that are rendered, pebbledashed or pointed with a lime mortar have
the ability to exchange vapour. If the breathable lime product is removed and
replaced with an impermeable cement rich product, this will trap moisture, very
often causing internal damp problems within the house or building.
Damp Proof Course Injection
We can provide many different damp proof course (DPC) Injection treatments,
selecting the product and application most suited to a particular substrates
requirement. Most treatments are now in a gel format which is pumped into a
series of holes drilled into the appropriate brick or mortar bed.
The installation of a damp proof course is only one part of the overall process.
Wet plaster and salt contaminated plaster must be removed and replaced. Both the
damp proof course injection and the replastering form part of the damp proof course
system and both are usually included in the full guarantee offered by Avant Coatings Ltd.
The installation of a damp proof course in a wall that is still wet and has evidence
of salt contaminated plaster, will not allow the wall plaster to dry out or for the
salts in the plaster to reduce. For this reason, plaster removal and replacement
is required. Too often we hear of, and visit properties where only the damp proof
course has been installed and the wall plaster still tests damp with a damp meter.
Types of Plaster
The correct type of replacement plaster in this process, must be a renovating plaster,
which is cement-based and does not contain gypsum in the backing or first coat.
Gypsum is salt and moisture sensitive and degrades in the presence of both.
The design of a renovating plaster is to provide two distinct layers. The backing
coat, is that applied directly to the exposed masonry, when the old plaster has been
removed. The backing layer’s primary purpose is to protect the finishing coat from
remaining moisture and salt left in the masonry once the old plaster has been removed.
For this reason, backing plaster contains both water and salt resistant additives.
The backing plaster is of a course nature, so after application, will dry with a
rough surface. This allows a good bond when applying the finishing plaster, which
can then be decorated after applying a smooth finish.
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