A high proportion of damp problems in buildings are caused by condensation, rain penetration or rising damp. Dampness tends to cause secondary damage to a building. The highest airborne mould concentrations are found in buildings where significant mould infestation has occurred, usually as a result basic structural dynamics pdf severe water intrusion or flood damage. Moulds can grow on almost any surface and occur where there is a lot of moisture from structural problems such as leaky roofs or high humidity levels.
Airborne mold concentrations have the potential to be inhaled and can have health effects. Externally, mortar may crumble and salt stains may appear on the walls. In extreme cases, mortar or plaster may fall away from the affected wall. Health concerns around mould include infections, allergenic or immunological illness, and nonallergic illness. Asthma is also triggered by the sensitization of dust mites accruing humid, wet regions of a structure. Another health effect associated with structural dampness is the presence of bacteria in an indoor environment. Bacteria requires water to grow and multiply.
Bacteria is a source for the transmission of diseases, therefore putting occupants’ health at risk by water intrusion into the indoor environment. Water removal and drying of wet building materials within 2 days will likely prevent mold and bacteria growth, therefore reducing occupants’ vulnerability to disease. A Visual Guide to Damp, Mold and Indoor Pollution. Exposure to microbial contaminants is clinically associated with respiratory symptoms, allergies, asthma and immunological reactions. Dampness has therefore been suggested to be a strong and consistent indicator of risk for asthma and respiratory symptoms such as cough and wheeze.
A wide range of instruments and techniques can be used to investigate the presence of moisture in building materials. When used correctly, they can provide a valuable aid to investigation. The competence and experience of the person undertaking the damp investigations is often of greater importance than the kit he or she carries. Experience and qualified surveyors are the difference between a correct and incorrect diagnosis of damp.
Chartered building surveyors are usually experienced in identifying dampness issues, however their reports often suggest that dampness problems are investigated by a specialist damp and timber surveyor with a CSRT qualification. Processes for diagnosing rising damp in buildings are set out in BRE Digest 245. Most forms of dampness can be prevented by thoughtful building design and careful construction. 15 cm above ground level, to act as a barrier through which water cannot pass.
Slate or “engineering bricks” with a low porosity were often used for the first few courses above ground level, and these can help minimise the problem. There are many approaches to the treatment of dampness in existing buildings. Key to the selection of an appropriate treatment is a correct diagnosis of the types of dampness affecting a building. Details of possible treatments for specific types of dampness are covered in the sections below. The cause of the dampness must first be eliminated, by providing better drainage or fixing leaking pipes.
Then, any affected plaster or mortar must be removed, and the wall treated, before replacing the plaster and repainting. Humidity occurs in indoor environments due to building related causes. Porous walls, rising damp, and leaks in the building are determinants for structural dampness due to elevated humidity levels. The construction of the building can also lead to humidity and unwanted moisture in the indoor environment. Wet materials, such as lumber stored unprotected outdoors before construction, can lead to increased humidity indoors for up to the second year of occupancy in the building. Most commonly in residences, elevated relative humidity is produced by poor drainage systems. This leads to dampness in substructures such as crawlspaces and basements.
The dampness results in vaporization where water vapor is transmitted into the building’s interiors. Water vapor may enter the building through supply air ducts in building slabs and circulated by warm forced air. Water vapor can also enter a building through leaky return air ducts in homes with crawlspaces. Human occupancy adds a significant amount of humidity to the indoor environment. Personal activity as basic as breathing and perspiration add moisture to an indoor space.
Cooking and showering raise humidity levels in the indoor environment, which directly affects the structural dampness of a home. Aspects of the home can also increase the humidity of a space. Items such as aquariums, indoor swimming pools, hot tubs, and even indoor plants add to the humidity of an indoor space. All of these attributes can increase the humidity of a home beyond its recommended thirty to fifty percent.