Symptoms
Dampness tends to cause secondary damage to a building. The unwanted moisture enables the growth of various fungi in wood, causing rot or mould health issues and may eventually lead toHealth effects of structural damp
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 require water to grow and multiply and certain species can cause disease in humans, thus the intrusion of water into an indoor environment can place the health of occupants at risk from bacterial infections. Water removal and drying of wet building materials within 2 days will likely prevent mould and bacteria growth, therefore reducing occupants' vulnerability to disease. ''A Visual Guide to Damp, Mold and Indoor Pollution'' stated that:Statutory requirements (UK)
Building Regulations
Section 5.2 of The Building Regulations 2010 Approved Document C, "Site preparation and resistance to contaminants and moisture" requires that buildings should be constructed to resist rising damp, penetrating damp, and condensation. Walls should: #resist the passage of moisture from the ground to the inside of the building; and #not be damaged by moisture from the ground and not carry moisture from the ground to any part which would be damaged by it, and, if the wall is an external wall: #resist the penetration of precipitation to components of the structure that might be damaged by moisture; and #resist the penetration of precipitation to the inside of the building; and #be designed and constructed so that their structural and thermal performance is not adversely affected by interstitial condensation; and #not promote surface condensation or mould growth, given reasonable occupancy conditions. Similar requirements are also made in reference to floors in Section 4 of the document.Homes (Fitness for Human Habitation) Act
The Homes (Fitness for Human Habitation) Act 2018 requires private landlords in England and Wales to ensure that houses that they rent are "free from damp.,"Identification
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. For example, it is sometimes found thatPrevention and treatment
Most forms of dampness can be prevented by thoughtful building design and careful construction. In the UK, well built modern houses includeHumidity
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. Humidity levels in an indoor environment need to be accounted for based upon season and temperature. If humidity levels do not agree with the time of the year and the temperature during seasons, mold infestation and deterioration of the building will occur due to moisture. An acceptable humidity level in indoor spaces ranges from twenty to sixty per cent year round. However, levels less than twenty per cent in the winter and levels higher than sixty per cent in the summer are deemed unacceptable for indoor air quality. Structural dampness is likely to occur as well as an increase of health risks associated with moisture damage.Prevention and treatment
There are strategies to prevent water infiltration due to humidity into structures, as well as ways to treat human occupancy practices regarding humidity. Vapor retarders are materials that can be used to restrain uncontrolled airflow and water vapor into an indoor space. Vapor retarders are used to decrease the rate and amount of water vapor diffusion through ceilings, walls, and floors caused by humidity. It is made of thin, flexible materials and its coatings can be installed by trowels or brushes. Utilizing vapor retarders in a building prevents structural dampness from occurring or continuing if it already exists. A strategy for reducing humidity levels in an indoor environment is by altering occupant activity and indoor mechanics. Kitchens and bathrooms need to have their own vents. Additionally, washing machines need to be vented outdoors. Both of these are important in order to decrease indoor moisture due to humidity caused by the activities occurring in these indoor spaces. Moisture sources, such as hot tubs or indoor swimming pools, should be covered by airtight lids when not in use, thus humidity levels stay low in the indoor environment///-.Condensation
Condensation comes from water vapour within the building. Common sources may include cooking, bathing, dishwashers, etc. The moisture in the air condenses on cold surfaces, sometimes inside the walls calledIdentification of condensation
If it is suspected that the problem is condensation, then a room should be sealed off with aTreatment
Typical remedies for condensation include increasing background heat and ventilation, improving the insulation of cold surfaces and reducing moisture generation (e.g. by avoiding the drying of clothes indoors).Rain penetration
Rain Penetration (also known as "penetrating damp"()) is a common form of dampness in buildings. It can occur through walls, roofs, or through openings (e.g. window reveals). Water will often penetrate the outer envelope of a building and appear inside. Common defects include: * Roof defects such as faulty flashing, cracked or missing slates or tiles. * Faults in the brickwork or masonry such as missing or crackedWalls
Rain penetration is most often associated with single-skin walls, but can also occur through cavity walls - e.g. by tracking across wall ties. Single-skin brick walls of standard thickness (9 inches) have been considered to provide inadequate resistance to rain penetration for many years, which is why cavity wall construction is now standard in the UK. The 1944 Housing Manual published by the Ministry of Works and the Ministry of Health stated that:''"The resistance to penetration of rain should not be less than that of 11-in. brick cavity wall, properly designed and constructed with attention to details at the heads and joints of openings. An unrendered 9-in. wall is regarded as substandard."''Whilst renders are often applied in an attempt to resist rain penetration, they must be maintained in good condition in order to fulfil this function. Even relatively small cracks in renders can allow rain penetration to pass into the underlying masonry. In his 1954 book, "The Restoration of Old Houses" Hugh Braun highlighted problems inherent in certain types of render that were widely used in the late eighteenth century and throughout the Victorian era: ''"By the end of the eighteenth century a number of patent water-repellent cements were appearing on the market, the most popular of which, roman cement, continued in universal use throughout the Victorian era; many old buildings were rendered with this substance. Its adhesion was poor and it will often be found that it has become separated from the walling over considerable areas and can be stripped away in large sheets."''
Primary Causes
* Porous masonry (i.e. under-fired bricks, porous stone, or porous mortar) * Cracks * Defective pointing * Unfilled joints and perpends, * Defective seals around doors and windows * Holes in walls – e.g. where cables or pipes protrude * Defective renderExacerbators of Rain penetration
Where a wall suffers from one or more of the primary causes of rain penetration listed above, the problem can be made worse by one of the following exacerbators of rain penetration: * Defective rainwater goods * Moss growth on roof tiles (causing blockage of rainwater goods) * Defective or missing window sills (causing high concentrations of rainwater to bear on section of wall below window) * Non-breathable coatings such as acrylic masonry paints – especially where applied to a poorly prepared masonry substrate * Location/aspect of wall – e.g. walls facing prevailing wind are more prone to rain penetration problems (see BS8104) * Periods of extreme rainfall – walls that are normally thick enough to prevent rainfall from reaching the inner face can be overwhelmed during periods of heavy, persistent rainfall Modifications to a building involving impermeable materials can also exacerbate the symptoms of rain penetration by trapping moisture. This can be a particular problem with regard to the installation of retrofit external wall insulation (EWI).Rising damp
Rising damp is the common term for the transport of water in the lower sections of walls and other ground-supported structures byHistory
The issue of rising damp has been a concern since ancient times. The Roman ArchitectSkepticism
Rising damp is a phenomenon that is fully predicted by the laws of physics, has been researched on a worldwide scale, and has been documented since Roman times. Nevertheless, a small number of people have expressed the view that rising damp is a myth and that it is, in fact, impossible for moisture to rise from the ground into the wall structure through pores in the masonry. A former chairman of the construction arm of the Royal Institution of Chartered Surveyors (RICS), Stephen Boniface, has said that 'true rising damp' is a myth and chemically injected damp-proof courses (DPC) are 'a complete waste of money'. However he has recently clarified this statement on a comment post made on the Surveying Property website, Konrad Fisher's article "The Fraud of Rising Damp" points out that the historic city hall in Bamberg stands in the river Regnitz and its bridge remains dry without any chemical, mechanical or electronic damp-proof course. However, proponents of rising damp suggest that not all walls are capable of supporting rising damp, so merely observing that rising damp does not occur in a particular wall does not disprove its existence in other walls. In 1997 the housing disrepair team at Lewisham Council in south London were so convinced that rising damp was a myth that they offered a reward of £50 to anyone who could show them a genuine case of it. Manager Mike Parrett said "The point of the reward is to convince our tenants that rising damp is a myth." Lewisham has never found a genuine case of rising damp and has never paid out the £50 reward. Water intrusion into the indoor environment can be attributed from causes other than rising damp. Moisture penetration has been an ongoing problem for residences as evaporation occurs at the edge of the damp area, resulting in "tide marks" due to salt deposition. The "tide mark" is commonly distinguished as a feature of rising damp. However, even after the water intrusion has been treated, these salt accumulations still persist. This suggests that rising damp is not always the cause for the water penetration. The Building Research Establishment (BRE) in its review concludes that rising damp is a real problem.How rising damp occurs
According toDiagnosis of rising damp
The first step in assessing damp is to check for standing water. Removing water with good drainage will remove any form of dampness. Once done, and dampness remains, the next step is to look for the presence of a damp-proof course. If a damp-proof course is present, it is likely to be functioning, as the materials from which damp proof courses are manufactured tend to have a long lifespan. However, it should be acknowledged that there are cases where existing damp proof courses fail for one reason or another. One indicator that is often used to determine if the source of dampness is rising damp (rather than other forms of dampness) is to look for the presence of salts – in particular a tell tale "salt band" or "tide mark" at the peak of the damp's rise. This is not a reliable method as salts and dampness can enter the fabric of the wall in other ways – e.g. unwashed sea sand or gravel used in the construction of the wall. If there is no damp-proof course and rising damp is suspected (tide mark, moisture confined to lower section of wall etc. ...) then a number of diagnostic techniques can be used to determine the source of dampness. BRE Digest 245 states that the most satisfactory approach is to obtain samples of mortar in the affected wall using a drill and then analysing these samples to determine their moisture and salt content to assist in providing appropriate remedial building solutions. The fact that this technique is destructive to the wall finish often makes it unacceptable to homeowners. It is for this reason that electrical moisture meters are often used when surveying for rising damp. These instruments are unable to accurately measure the moisture content of masonry, as they were developed for use on timber, but the reading patterns that are achieved can provide useful indicators of the source of dampness.Rising damp treatment
In many cases, damp is caused by "bridging" of a damp-proof course that is otherwise working effectively. For example, a flower bed next to an affected wall might result in soil being piled up against the wall above the level of the DPC. In this example, moisture from the ground would be able to ingress through the wall from the soil. Such a damp problem could be rectified by simply lowering the flower bed to below DPC level. Where a rising damp problem is caused by a lack of a damp-proof course (common in buildings over approximately 100 years old) or by a failed damp-proof course (comparatively rare) there are a wide range of possible solutions available. These include: * Replacement physical damp proof course * Injection of a liquid or cream chemical damp proof course (DPC Injection) * Damp-proofing rods * Porous tubes / other evaporative * Land drainage * Electrical-osmotic systemsReplacement physical damp proof course
A physical damp proof course made from plastic can be installed into an existing building by cutting into short sections of the mortar course, and installing short sections of the damp proof course material. This method can provide an extremely effective barrier to rising damp, but is not widely used as it requires experienced contractors to carry out if structural movement is to be avoided and takes considerably longer to install than other types of rising damp treatment. The cost is also several times higher than for other types of rising damp treatment.Injection of a liquid or cream chemical damp proof course (DPC Injection)
Injection of a liquid or cream into bricks or mortar is the most common method of treating rising damp. Adolf Wilhelm Keim describes the use of a hot bitumen remedial damp-proof course that is injected into holes drilled into a wall in his 1902 publication "The Prevention of Dampness in Buildings." Liquid-injection products were introduced in the 1950s and were typically installed using funnels (gravity feed method) or pressured injection pumps. The effectiveness of liquid injection damp proofing products is dependent on the type of formulation and the skill of the installer. In practice injection times tend to be lower than those required to provide a damp proof course of optimum effectiveness. A paper published in Building and Environment in 1990 made the following calculations about injection times:=Damp-Proofing Creams
= Since the early 2000s, damp-proofing creams have taken over from liquid products due to improved ease of application. As with liquid products these are based on silane/siloxane active ingredients which line the pores of the mortar to repel damp. The effectiveness of liquid and cream based rising damp treatments varies considerably between products due to variations in product formulations. Independent test certifications such as British Board of Agreement (BBA) certificates are available for some products, showing that they have met a minimum requirement for product performance - see #Damp_(structural)/Effectiveness_of_rising_damp_treatments As with liquid injection systems, cream based treatments rely on the competence of the installer for treatment to be successful. Injection holes need to be fully cleared of drill dust and debris before the cream is injected, and it is often difficult to know if each injection hole has been completely filled with cream. Furthermore, damp-proofing cream can sometimes drip out of the injection holes after treatment, reducing the effectiveness of the damp-proofing treatment.Damp-proofing rods
Damp-proofing rods use similar active ingredients to those found in liquid or cream-based rising damp treatments, but contained in a solid rod. They are generally considered to be easier to use than other types of rising damp treatment as the method of installation is simply to insert them into the correct sized holes drilled into a mortar bed. Damp-proofing rods are available with BBA approval. The rods are placed into holes drilled in the mortar course and the active ingredients diffuse along the mortar line before curing to form a damp-proof course. Damp-proofing rods are usually supplied in 180mm (7") lengths suitable for inserting into a 9-inch thick wall. For treating half-brick thick (4.5 inch) walls, the rods are simply cut in half. A benefit of damp-proofing rods compared with damp-proofing creams and liquids is that it is possible to guarantee a consistent dose of active ingredient into each hole drilled in the mortar course – i.e. it is impossible to under-fill the holes.Porous tubes
Porous tubes are installed along a mortar course. In theory these encourage evaporation and reduce the rise of the damp. Independent test certification are available for this type of product and tests carried out by the Building Research Establishment suggest that they are effective at controlling rising damp.Land drainage
It has been suggested that improving drainage around walls affected by rising damp can help to reduce the height of rise by reducing the amount of water available to be absorbed into the capillaries of the wall. Typically a trench would be excavated around the affected wall into which a porous pipe would be laid. The trench would then be back-filled with a porous material such as a single-sized aggregate, forming a French drain. Such a system would obviously have the practical disadvantage of being suitable only for the treatment of outside walls and would be impractical where other buildings are close by or where a building has shallow footings. Although the theory of reducing rising damp by reducing the amount of moisture in the underlying ground would appear to be sound, there is little data to suggest that it is effective in practice. Indeed, G and I Massari stated in the ICCROM publication "Damp Buildings Old and New" that little effect was observed with "open trenching" and no effect was observed with "covered trenching."Electrical-osmotic systems
These attempt to control rising damp through the phenomenon of electro osmosis. Whilst there is evidence to suggest that these systems can be useful in moving salts in walls there is little in the way of independent data to demonstrate effectiveness in treating rising damp. The BRE publication "Understanding Dampness" makes the following observations about electro osmotic systems for the treatment of rising damp:Effectiveness of rising damp treatments
BRE Digest 245 suggests that with the exception of replacement physical DPCs, only methods of treatment with third party accreditation (e.g.Replastering
Replastering will often be carried out as part of a rising damp treatment. Where plaster has become severely damaged by ground salts there is little argument about the need to replaster. However, there is considerable debate about: # The extent of replastering required # The use of hard sand:cement renders to replaster as part of a rising damp treatment BS6576:2005 states that "the function of the new plaster is to prevent hygroscopic salts that might be present in the wall from migrating through to its surface, while still allowing the wall to dry." However, writing in the RICS publication "Remedying Damp", Ralph Burkinshaw claims that, "the plaster is really there for main reasons." He accepts the need for replastering when significant amounts of ground salts have built up in the existing plaster, but he then goes on to say that replastering is often carried out to make up for an unreliable chemical DPC. He also suggests that damp-proofers have an incentive to carry out more replastering than is strictly necessary as it allows them to finish the job without having to wait for walls to dry out, resulting in faster payment. Although the sand-cement renders typically installed as part of a rising damp treatment are very effective at holding back damp and ground salts, they have a number of disadvantages. These include an incompatibility with the soft bricks and mortars encountered in older buildings and a lack of insulation properties compared with more traditional plasters, resulting in an increased risk of condensation. Replastering is also one of the most expensive parts of a rising damp treatment. Porous renders to German WTA specification 2-2-91 can be used as an alternative to dense sand-cement renders. These have a minimum porosity of 40% of total volume. Salts crystallise in these pores rather than on the plaster surface, avoiding decorative spoiling. Such plasters offer a better solution than dense sand-cement renders when used on moderately salt-contaminated walls as their porous nature gives them insulation properties, resulting in a warmer surface temperature and making condensation problems less likely to occur. However, when used on heavily salt contaminated walls they may need to be replaced frequently as they lose effectiveness once all the pores have become filled with crystallised salt. The "Renovation Mortars" described in EN998-1:2003 are described as being designed for use on "moist masonry walls containing soluble salts." The performance requirements for these types of mortars are based on German WTA specification 2-2-91 but without the requirement for a minimum porosity of 40% of total volume. More recently, systems have become available that allow plasterboard or insulation board to be used to replaster walls affected by rising damp. After the existing plaster has been hacked off the wall, a salt and moisture retardant cream is applied to the wall. The plasterboard is then applied to the wall using a salt/moisture-proof adhesive. Such systems have the advantage that they can be decorated straight away, rather than having to wait several days or weeks (as would be the case with standard plasters). They also provide a warmer surface that is less prone to condensation than would be the case with a standard sand:cement render. Replastering may not be necessary where salt contamination is not severe. BS6576:2005 states that "Where the plaster appears to be in sound condition, the extent of plaster to be removed may be minimised by delaying any decision to replaster until the drying period is complete." Avoiding the need to replaster in this way can reduce disruption and mess and has the advantage of allowing the original lime or gypsum-based plaster to be maintained. However, the deficiencies of any remedial damp-proof course will be more apparent if the wall is not covered with a waterproof render. For this reason it is important to check the BBA certificate of the damp-proofing system to ensure that it is valid for use where replastering is not being carried out.Redecoration
It is best practice to delay replastering and redecoration for as long as possible following rising damp treatment, but this obviously creates inconvenience to the occupants of the affected building. BRE Digest 245 states that "While the wall should be allowed to dry for as long as possible, replastering can follow, providing porous decorations are selected. These are usually matt emulsions and water-based paints, both of which will allow the wall to breathe. Application of gloss and vinyl paints or wallpapers should be delayed for at least one year." Plasterboard-based replastering systems have the advantage that immediate redecoration is possible irrespective of which decorative finish is chosen. Due to the fact that rising damp often co-exists with other forms of dampness such as condensation, the use of a mould resistant emulsion paint is often recommended.In popular culture
In ''The Sopranos'' episode "Calling All Cars",References
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