Damp Effects in Buildings
Damp Information for damp proofing that is used in the construction industry as a barrier. In conjunction with other building practices to prevent moisture from passing from the external to the internal. The barriers are designed to stop moisture travelling vertically or horizontally through porous material such brick, block or render.
Information for damp proofing material that is defined as a material that resists the passage of water. With no hydrostatic pressure and waterproof as a treatment that resists the passage of water under pressure.
The consequences of dampness in buildings can range from the trivial. like mould around a window seal to the catastrophic such as floor joist and main support timbers collapsing.
These are some of the most common problems found in properties. Which suffer from some form of dampness and the reasons damp proofing is required to remedy these damp issues.
- Visible Dampness
- Hydroscopic Salts
- Fungal Decay Damp
- Damp Mould Growth
- Damp Deterioration
- Damp Health Hazard
- Damp Corrosion
- Increased Heat Loss Damp
In many cases, the consequences of dampness will include a combination of these effects and will require several damp proofing solutions to remedy the problem.
Damp information for visible dampness problems that are unsightly but may be ignored by the occupant of a building. If they only appear to affect the external surface of the building.
Staining of the external walls of a building by water from defectives. Such as down pipes and gutters or by earth bridging horizontal damp proof courses. And faulty water overflow pipes seems sometimes to be considered as enchanting the character of the property.
However, buildings will only accept a limited amount of punishment and if the warning signs are not recognised. Then far more serious consequences will eventually result from such neglect.
Internal Visible Dampness
Internally, visible dampness problems are taken more seriously. If they are continuing problems, especially if they affect the internal decoration.
An established rising damp or penetrating damp problem may mean that the lower part of the wall always appears to be wet. And that no matter how often the internal decorations are renewed, deterioration quickly occurs.
Transient dampness problems, however, may well be conveniently ignored due to lack of understanding as to the hidden consequences that may exist. For example, condensation on a window is easily dealt with by regular use of a cloth until the time that extensive fungal decay becomes evident in the timber frame.
It is important to realise that though the visible consequences of dampness within and outside the building. It may appear of little importance, the consequences could be very serious.
Hence the survey of a building related to possible dampness problems has to take this into account. And then identify the hidden consequences associated with the visible problems, for example:
If one wall of a building has a visible dampness problem due to rising damp. Then do the other walls also have rising damp even though the problem is not yet visible?
If the cause of dampness has been identified for a visible problem on the walls of a building. Is there a hidden problem (Fungal decay) affecting the timber in contact with those wet walls?
Damp information about salts that may cause problems in buildings for a number of different reasons:
- They may appear as unsightly surface deposits (efflorescence) on the internal or external surfaces. And the continual need to be brushed off to maintain the appearance of the building.
They may crystallise below the surface and disrupt the surface of the material. Common examples are:
The Crystallisation of salts beneath the surface of the external facing brickwork, this will lead to spalling of the brick face.
The Crystallisation of salts on the surface of brickwork and below the plaster finish, this will show on internal wall surfaces leading to disruption of the plaster finish.
- They may chemically attack materials within the building fabric, for example:
Sulphates chemically react with Portland cement and if the sulphate concentration is high enough. The deterioration of Portland cement based materials (mortar, internal plaster, external render) will occur. These Chlorides will corrode copper and cause extensive deterioration of copper water pipes.
They may be hydroscopic which means that the material. In which they are contained will become wet under high humidity conditions.
In all cases the salts are in the material to stay, unless they can be transported by water to the surface of the material. Or unless the material it’s self is removed and in some cases there is no simple answer to the problem that exists.
It is important to remember that the salts only cause a problem if there is a source of water available to them. And if they are present in sufficient quantity. Therefore, if the source of the water can be removed, the consequences can be eliminated.
This is precisely what should happen when a wall is re plastered following a rising damp treatment.
Fugal Decay Damp
Damp information about the attack of timber by wood rotting fungi will only occur if the following five conditions are met.
- A source of infection (a fungal spore)
- A supply of food (Timber)
- A supply of oxygen (Air)
- A suitable humidity (60%+)
- A water supply
In most buildings, the first four conditions are usually satisfied and so the source of moisture is the trigger for fungal decay to occur.
In any building in which there is a dampness problem. It should be assumed that there is likely to be an associated fungal decay problem with the timbers. In the vicinity of the wet areas, this should be taken into account during any survey for dampness in buildings.
Damp Mould Growth
Damp information about the disfiguration of surfaces mould growth by is common in buildings with a dampness problem. Though the occurrence of such mould growth should not be taken as indicating any particular type of dampness condition.
Moulds are simply another type of fungi, which feed of the deposits which collect on the surface of materials but which cause no real damage to that material.
The presence of mould growth in a building may indicate that a dampness problem exists. Or may simply be the result of high humidity conditions within the building.
It should be not therefore be assumed that the resolution of a known dampness problem will eliminate mould growth. If the real cause of the problem is a high humidity condition. Then some additional course of action will also be necessary.
Damp information about the continual wetting and drying of materials will often cause physical degradation of the material. Although obviously materials vary considerably in their tolerance to such conditions. Some common consequences are shown below:
The material expands as the moisture content increases and contracts. As the moisture content decreases resulting in cracks appearing in the material. Common examples of this are the cracking of internal plaster, external renders, timber and surface coatings, such as paint.
If the material is rigidly fixed and expansion occurs, it may distort as well as crack. Common examples are distortion of timber skirting boards and the loss of adhesion to plasters and renders.
The material becomes wet, the temperature drops to below 4 C, and the water expands and eventually freezes at 0 C causing the face material to spall off.
This is commonly seen as frost damage to external facing brickwork.
The evaporation of water from the material is restricted by a coating on the face of the material. And results in the coating being forced off the face of the material.
The wetting and drying process cause salts to migrate and concentrate at or the surface of the material and lead to the problems described in Hydroscopic Salts.
Damp Health Hazard
Damp information about the relative humidity of air within a building can have an effect on occupants of the building.
If the relative humidity is low (below40%), water evaporates from the skin with relative ease and the body feels cold.
If the relative humidity is between 40% and 60%,. iit becomes more difficult for water to evaporate from the skin and the body temperature increase. At very high levels of relative humidity (80% to 90%). The result can be serve headaches and a general feeling of lethargy. Obviously, this situation is more likely to be encountered in buildings with dampness problems.
Additionally, if the dampness problem also has an associated fungal decay or surface mould growth problem. The presence of large quantities of fungal spores in the air can have an adverse effect on the health of the occupants.
Damp information about water corroding iron based materials, such as steel wall ties. And in conjunction with salts, will also corrode other metals, such as copper. Hence, corrosion of metal components. Such as pipes, wall ties and timber connectors, in contact with wet materials can be a serious problem.
Increased Heat Loss Damp
As the moisture content of materials increases, so their ability to conduct heat increases. This clearly has some effect on the rate of heat loss from a building but, more importantly, increases the risk that condensation may occur.
Damp Proofing Survey
The need for the correct damp proofing advice is so important. There are so many variables only our experienced surveyor can choose the best method of repair for your property.
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