Rising damp is distinct from other forms of dampness and moisture, such as rain penetration and condensation, which require different methods of treatments.
Compared to solutions & systems used by damp-proof specialists and other trades people, such as an injected damp-proof course, a physical damp-course & the electrical lectros electro-osmosis damp-proofing system which an ideal rising damp control method, for stone cottages and barn conversion projects.
Rising damp problems are not limited to the UK, but are found throughout the world where there is moisture present in the earth below a building.
Ninety five percent of the properties that we survey have had a physical damp-proof course installed at the time of construction. This will usually be slate for older properties and for houses built after the 1930’s it is often hessian impregnated with bitumen.
Physical damp-proof courses will still be very effective for controlling rising damp and there should never be any need to install a chemical damp-proof course but the vast majority of non – independent damp surveyors (who are usually paid on a commission only basis) will always state ‘rising dampness caused by the breakdown or lack of a damp course was found and we recommend chemical damp-proofing to all ground floor walls, in other words they try and sell you a product you don’t need!!!
In reality physical damp-proof courses rarely breakdown and even if there has been some minor cracking of the damp proof course it will still be effective in preventing rising damp from the ground. Even if there is no damp-proof course present then ‘rising damp’ can be controlled by ensuring that the take up of moisture from the ground is less than the evaporation rate from walls by installing drainage channels etc to remove any moisture reservoir effect.
There are many reasons why you may want to arrange a rising damp survey, which may include the following,
A rising damp survey on a property for house purchase and homeowners who may have found a specific damp problem in a property and needs walls tested for rising damp & adjacent sub-floor inspected for wood rot, timber decay & woodworm infestation.
A property purchaser, who has had a structural survey carried out and damp issues have been highlighted, with the recommendations of a further damp and timber survey to be carried out by a (PCA) property care association registered damp proofing specialist Company.
A building contractor who is working on your property and found damp problems and signs of wood boring insects & wood rot decay.
A property management company who has been informed of damp issues by their tenants.
Our rising damp surveyors have been carrying out surveys on buildings to identify damp issues for over 40 years.
What is rising damp?
Rising damp is the upward movement of moisture through damp walls, and sometimes floors, by capillary & diffusion action from below the ground. It occurs at ground floor level in lower portions of external and interior partition walls.
The height to which rising damp will rise depends on the size of the capillaries within the building material, the amount of moisture in the ground (water table level) and the evaporation rate from either face of the wall surface.
As a general rule, the smaller the capillaries of the structure the higher the water will rise. However, the height of rising damp usually does not extend much further than approximately 1 meter above ground level. Modern buildings, in Great Britain, prevent & control rising damp in houses with a system of damp proofing barriers – a physical damp proof course (DPC) has been required in walls since 1875 and damp proof membranes (DPM) in floors from the 1960’s. Most old buildings lack these and therefore rising damp can occur.
However, the presence of a damp proof course does not guarantee that rising damp will not occur. If the continuous run of the dpc has been bridged or broken then dampness can appear in the wall.
Tidemarks and damp stains on walls
Wet damp patches on walls
Bubbling or flaking plaster on walls
Damp and musty smell in rooms
Wooden skirting & floor boards starting to rot
Black mold appearing on walls
What is Damp-Proof Course (DPC)?
A damp-proof course prevents damp from the ground rising up the walls and damaging your property. Properties which have no appropriate damp protection layer or has a damaged damp course may be affected by excess moisture from the ground. This excess moisture can affect plaster, decoration and can even result in wet rot, or dry rot affecting unprotected timbers.
Most properties which exist today should have a damp-proof course which is evident at a minimum of 150 mm above ground level. This may appear as a mortar course with a bitumen or plastic DPC sheet poking through.
These materials tend to be very effective, unless the building movement result in them cracking or the DPC is bridged or the older bitumen material breaks down due to old age. Damp-proof courses are required in all new build properties in order to prevent rising damp from occurring.
As noted above there are many factors which can result in a damp-proof course failing. One problem which our specialists commonly encounter is that building renovations have raised the ground level above the existing damp-proof course.
This allows the moisture from the ground to bypass the DPC and let moisture penetrate the property. If this occurs, we would recommend that the ground be reduced to 150mm below the original DPC or if this cannot be done then a new damp-proof course will need to be installed. The first step would be to get a specialist damp surveyor to inspect your property and give the correct diagnosis of a damp problem and how it could be fixed.
Rising Damp is Widely Misdiagnosed
Rising damp is widely misdiagnosed in existing properties by damp companies, based on the incorrect interpretation of visual evidence and the readings of moisture meters. Because of a highly successful sales campaign for over 30 years by specialist remedial damp-proofing contractors installing injected ‘chemical damp-proof courses’, this misdiagnosis of rising damp has also become synonymous with a diagnosis of a lack of an ‘injected chemical damp-proof course’.
Although this has been very good for damp-proofing companies, it has often resulted in a waste of the clients’ money and resources; original plasters and finishes have been destroyed in the process of installation, and unnecessary damage has been caused to original structures by the drilling of irrigation holes. In addition, money that might have been spent on more cost-effective maintenance or repair works has been wasted.
Whilst injected chemical damp-proof courses may provide some protection for certain types of structure if properly specified, their general application is rarely the most cost-effective way of controlling damp problems in buildings, and may be wrongly specified and ineffective. In particular the more generally available water based products may only form an effective ‘hydrophobic band’ if applied to a dry wall after it has dried out. This can prevent their effective installation in damp walls.
Rising Damp Treatment Specialists
The best way to stop rising damp becoming a serious problem is to arrange a property survey with Adept UK Property Care specialists. If you think your property is suffering from rising damp then our experienced independent rising damp surveyors can visit your property, properly diagnose the problem and build an effective damp treatment plan specific to the needs of your property.
Rising Damp Treatment Survey & Report
To determine the full extent of rising damp and the appropriate method of treatment your building damp surveyor will suggest you to get a rising damp survey. Experience from a fully qualified, expert damp surveyor can be the difference between a correct and incorrect diagnosis and treatment recommendations for a damp problem – saving you £1000s.
Approved rising damp surveyors will have a CRDS (Certificate in Remedial Damp Surveying) or a CSRT (Certificate in Remedial Treatment), so make sure you don’t use under-qualified rising damp surveyors / under insured trader.
Rising damp can cause serious damage, to both your property and your health, so if you have any concerns about damp in your home, get an independent damp surveyor to advise you on whether you need to get a rising damp survey.
Rising Damp Treatment & Damp Damage to Property
The damage caused by rising damp is more than just aesthetic. It can lead to the structural deterioration of plaster and brickwork, rotting of timber frames and the rusting of steel and iron fasteners.
If rising damp is left untreated the damage can be costly to repair and due to the nature of the damage caused by damp it is likely that plastering and redecoration will be needed – a further expense.
If you’re buying a property be sure to get a rising damp survey carried out by a damp specialist who can provide you with a damp and timber report to make sure there are no underlined damp and decay problems that would need further investigation. This will give you an opportunity to reopen price negotiations with the seller and possibly reconsider your purchase.
Rising Damp Treatment & Control Systems
Rising damp is fairly slow to develop and may be present for several years before any symptoms become apparent. Eventually rising damp may show as a tide-like damp stain on walls with little or no damage above, but below the paint may be blistering, wallpaper stained and peeling, the wall plaster damaged and skirting boards showing signs of timber decay. External signs of rising damp are darkening of the lower brickwork, white salt marks and even spalled (damaged) brickwork. Floors can display moist patches and damp staining.
Only as a last resort should a chemical damp-proof course be installed
Before considering the installation of a chemical damp-proof course to cure rising damp, the Adept UK specialist surveyor will carry out a rising damp survey to assess the damp problem and ascertain the exact cause of the dampness or moisture and establish the need for rising damp treatment. Factors such as high external ground levels, poor surface drainage, defective gutters and down pipes can all cause the damp-proof course to be bridged, leading to the symptoms of rising damp.
(How extensive is Rising Damp?) By addressing any or all of these defects and allowing the damp wall to dry out naturally, then in most cases the need & cost for the installation of a chemical damp-proof injection or damp proof course (dpc) is avoided. Only as a last resort, is a chemical damp-proof course installed.
Should the Adept UK surveyor, after carrying out a rising damp inspection both internally and externally, and eliminating all other causes such as condensation and penetrating damp, diagnose rising damp, then he will assess the extent of the dampness and the need for re plastering.
A damp report and/or damp quotation will be provided outlining the most cost effective solution or remedial treatment to the damp problem. The pre-purchase damp survey & report issued will satisfy the mortgage loan providers & all other major lenders.
Rising Damp Treatment Chemical injection damp-proof courses.
Contrary to a minority view, rising dampness does occur and is not that uncommon in properties without physical damp-proof courses (just put a brick/mortar in water and watch it wick). Where rising dampness does occur and warrants remedial action then a chemical injection damp-proof course may be considered.
Over the years there have been a number of problems of continued dampness following the insertion of a chemical injection damp-proof course. However, considerable argument can arise as to whether the problem is due to the damp-proof course, re plastering or other factors: this tends to form the basis of related disputes.
Chemical injected damp proof-courses and re-plastering:
Injection damp-proof courses basically consist of the injection of a water repellent or pore blocking material into the base of a wall where it will form a diffuse band to ‘control’ the rising dampness.
Unlike a physical damp proof course which provides an impervious barrier and hence an immediate cut in rising water, the chemical systems will generally only control the rising water — not stop it. There are a number of physical factors related to the substrate and injection processes which govern why this is so. Thus, with chemical injection systems the lower part of a wall may always remain damp.
Therefore, to provide a non-spoiling decorative surface re plastering is required. Removal of the old plasterwork removes potentially heavy contamination with hygroscopic/deliquescent salts which have accumulated over many years of rising damp and which, if left, may spoil new decorations. However, the new plasterwork has a very important function — it must be capable of preventing hygroscopic/deliquescent salts passing to the new surface from contaminated underlying masonry.
This function is extremely important because (a) walls take time to dry down, and (b) the lower part of the walls are always likely to remain damp because of the limitations of the chemical injection systems. Fundamentally, chemical injection damp-proofing is a system — the injection of the damp proof course to ‘control’ the rising damp, and the re plastering to prevent future spoiling — the processes are inseparable.
Rising Damp Treatment
As rising damp control experts we will carry out the most appropriate damp proof treatments to cure any rising damp problem. Inserting a chemical damp-proof course (DPC) to control rising dampness involves the drilling of the brickwork / mortar to pre-determined depths of external and/or internal walls and then injecting the damp-proof course fluid.
The installation of a chemical damp-proof course in a house provides an impermeable damp proof barrier at low level in many structures from older stone built cottages, to brickwork in Victorian & modern houses to prevent further rising damp occurring.
This is the most common form of damp-proofing treatment used by chemical injection dpc contractors when controlling damp in homes nowadays and is considered to be the most cost effective rising damp treatment method of installing a damp-proof course in a house.
Rising Damp Treatment in Old Houses.
We are often asked – How do damp surveyors check and test walls for rising damp, how much does rising damp treatment cost / How much does a chemical damp-proof course cost to install in old houses?
The average cost of treating rising damp or the cost of installing a damp course (damp proofing) varies depending on the type of property i.e. terrace, bungalow semi-detached, house, flat etc. Firstly, a damp survey has to be carried out by a fully qualified C.S.R.T. specialist damp surveyor to correctly identify the dampness and determine if it really is rising damp, and in need of damp-proof treatment.
Other sources of moisture have to be eliminated, such as penetrating damp, condensation, plumbing leaks etc. before even considering if rising damp is present in a property. The construction of the building also has to be taken into consideration. Therefore there is no standard cost for damp proofing a house, as each individual property is different from the next.
Damp proofing prices differ between each individual timber and damp proofing remedial company and the type of damp proofing system used for controlling rising damp. Many properties we surveyed resulted in no damp proof course injection being required therefore substantial savings were made compared to the average cost of damp-proofing and woodworm treatment to a house. This can easily amount to thousands of pounds.
If you notice tide marks on your walls, peeling paint, wet patches or damaged skirting boards, you may have a rising damp problem, which most commonly affects older properties. Rising damp occurs when porous materials, such as mortar, bricks and stone, soak up moisture, and the dangers include timber decay, wet rot, various health conditions and more. Whether it’s due to the damp-proof course in your walls being ineffective, poor ventilation or a drainage problem, it’s crucial to resolve the issue promptly for the sake of your comfort, finances and home’s condition.
Rising Damp Treatment & Control Options For Controlling Rising Damp in External & Internal Walls
There are other alternative damp-proofing systems & damp treatment methods available for controlling rising dampness such as: Diffusion System. This rising damp control system involves the slow diffusion of a damp proofing cream into the mortar joints of brick or stone walls, which then forms a water repellent barrier to prevent further rising damp.
This is properly the best rising damp treatment system
Damp-Proofing Cream. came on the market in 2000, Dryzone Damp-Proofing Cream has caused a revolution in the treatment of rising damp and is used by many damp proofing companies in the UK. This damp proofing System now outsells chemical injection damp-proofing treatments and is the best-selling rising damp treatment?.
Electrical Osmotic damp-proof course system (Electro-Osmosis) used for rising damp control. This a chemical free environmentally friendly damp proofing option for controlling rising dampness involves inserting a continuous titanium band in the mortar joints and the insertion of electrodes. This electro-osmotic damp-proofing system method relies upon an electrical supply to prevent further dampness from rising up the wall, but the band and electrodes are easily damaged.
It is worth bearing in mind, that during the selling of your house or the buying of a property which has an osmotic electrical damp-proofing system installed, it should be switched off before the home buyer / valuation surveyor tests the walls for dampness, as high moisture content meter readings will be recorded during a rising damp survey ( these high readings are often mis-diagnosed as rising dampness) giving a false impression that possible rising damp is present, thus incurring potential costs for unnecessary remedial rising damp control work.
This damp-proof course system was introduced to Britain by W J Holmes of Rentokil and was installed in many houses by Rentokil in the UK between 1962 and 1974 before being superseded by the ever popular injected damp-proof course method used for rising damp control. Physical Membrane or Physical damp-proof course insertion (DPM) which, although effective, is laborious and disruptive to install and there is risk of damage to the structure. This dpc is also difficult to insert into party walls and impractical with random stone rubble walls. to arrange a survey please fill in our contact form
What is damp?
Put simply, damp is the localised, excessive build-up of naturally-occurring moisture that has no means of escape. While we have different names for damp, depending upon where and how it presents itself, for the most part, the terms are virtually meaningless; the root of the problem is almost always excess moisture.
What types of damp are there?
Condensation
The most common type of damp found in buildings is condensation. The causes include cooking, breathing, sweating, bathing, washing clothes and drying them on radiators. What happens is that warm air containing moisture from these activities hits something cool, like a wall or window, and because cold air holds less water than warmed air, droplets form.
In the UK, the time when condensation is at its worst is between October and April, when we are less likely to have open windows.
To eliminate condensation, moisture production needs to be reduced. This can be as simple as opening a window; for much of the year, the air outdoors has a lower humidity level than the air indoors.
Dehumidifiers can also help with reducing condensation, as can improving ventilation through systems like air bricks, trickle vents, humidistat fans, and creating positive pressure. Also, increasing air temperature (which results in increased surface temperature) can help.
Penetrating rain
When we talk about rain penetration in buildings, we are talking about the above ground admission of rainwater via some point or points in the structure’s envelope, generally as the result of gravity, wind pressure or capillary action. As a rule, penetrating rain typically affects south-westerly facing walls the most. In the UK, one of the primary causes of penetrating damp these days is poorly installed cavity wall insulation.
Cavity walls were actually developed to prevent water from penetrating the inner structure, serving as a kind of weather shield. However, when insulation is introduced, a bridge is created between the outer and inner walls, allowing the water access to the interior of the building. Other common points of entry include cracked exterior cladding, roofs, chimneys, roof lights, dormers, poorly fitted vents, and doors and/or windows.
The best way to address penetrating rain is to eliminate the cause. This can be as simple as clearing gutters of debris, repairing a crack, or replacing roof tiles. If the cause cannot be eliminated, there are solutions such as colourless, breathable water repellents that provide protection without changing the appearance of the brick or masonry, and ventilated dry lining systems
Rising Damp is it a Myth?
Today, the most popular damp proofing is chemical. An effective chemical course tries to mimic the performance of a solid physical course as close as possible. For salt problems, the solution is typically re-plastering. Sand and cement renders, while highly effective, are not suitable for heritage buildings. Plus, they tend to decrease the surface temperature, which increases the risk of condensation.
They are also reliant upon the user getting the ratio right. Pre-packaged renovating plasters provide a more consistent mix than mix-yourself versions, and they are less dense, which results in warmer surfaces. For quick turn-around, lightweight plaster can be used in conjunction with plaster membrane; however, damp can rise above it, if an adequate DPC isn’t installed. There are also salt retardant primers and salt-resistant breathable adhesives that can be used.
The other way rising damp can affect a home is through solid floors. However, before any source of damp can be accurately determined, issues like leaks, spills, flooding, hygroscopic salts around chimneys and fireplaces, and any existing construction moisture needs to be addressed.
Flooding
Although comparatively infrequent, a fourth source of moisture damage is flooding; where a structure is overwhelmed by water in a short period of time. In this case, water can enter the building as a result of extreme weather conditions or via a faulty system (leaks in water supply or heating system, blocked drainage, etc.) Flooding is typically a short-lived issue (hours or days vs weeks or months); however, the contaminants that often accompany the water can sometimes be more difficult to address than the water damage itself.
Other problems of damp
While damp itself causes problems, there are secondary problems associated with damp that not only cause problems with a building and living environment, but can be detrimental to an occupant’s health.
Mould
Mould is the common term used to describe the various types of fungi that thrive in moist areas. Water produced by condensation is ‘pure’ (distilled), making it an ideal medium for mould growth.
Actively growing mould is not only damaging to the material that it lives on – which can compromise the structural integrity of a building – it is also damaging to the inhabitants of that building. People who spend extended time in a damp, mouldy environment can develop problems like respiratory ailments, allergies, infections and other irritations.
In addition to mould, damp environments also provide a place where dust mites and bacteria can thrive. The breakdown of the bacteria and/or mould results in volatile organic compounds which cause a musty odour, while the breakdown of the material on which mould and bacteria grow can also result in airborne chemicals, gases and particulate matter.
Measuring moisture content
There are two types of moisture that can be residing (and therefore measured) in any building material: hygroscopic and capillary. Hygroscopic moisture is inherent to all building materials, and the amount is dependent upon certain factors, such as humidity. This type of moisture is to be expected and isn’t damaging. What is potentially damaging is the capillary moisture.
Capillary moisture is the non-inherent, excess moisture left in soil after any gravitational water has drained away. It is the result of surface tension holding moisture in place; creating a moisture film on particle surfaces and filling the spaces in-between particles.
Capillary moisture uses surface tension forces to move through the soil, wicking into plants or, in our case, into building structures it comes into contact with, without aid from (and even opposing) external forces such as gravity. This movement is generally referred to as capillary action, capillary motion and/or wicking.
Measuring moisture in walls
There are various ways to measure moisture content, depending upon what type of material you’re working with and the conditions that you are working in.
Electrical moisture meters: while electrical moisture meters serve a purpose, they must be used and understood properly, or else you can come away thinking that you’ve got a moisture problem when you don’t or vice versa.
The primary issues with electrical moisture meters are 1) they can be misleading in that they don’t accurately measure dampness in masonry substrates, and 2) the reading is dependent upon the probe’s area of contact with the substrate; that is, your readings can differ according to how well the probes penetrate the material. It is also important to recognise that these types of meters are incredibly sensitive to certain kinds of soluble salt contamination and small amounts of free moisture.
Taking samples: BRE Digest 245: A more accurate means of determining moisture content is by testing samples. Unfortunately, sample-taking is an invasive procedure that many building owners are not inclined to want performed. BRE’s Building Research Digest 245, Rising damp in walls; Diagnosis and treatment recommends that brickwork samples are taken for laboratory analysis using carbide or gravimetric testing. While taking brickwork samples does result in 10mm in diameter holes being drilled, it is far better than having plaster removed to install a chemical damp proofing course that might not actually be necessary.
Carbide test: In this test, brick or plaster dust samples are placed in a pressure cylinder along with calcium carbide. Any moisture present in the sample reacts with the calcium carbide and acetylene gas is formed.
The amount of gas formed is directly related to the amount of actual moisture found, which can then be read by a pressure gauge. This reading is far more accurate than an electrical moisture reading, as it eliminates salts and other issues that create misleading results. While the carbide test provides overall moisture content, it does not provide information regarding which is hygroscopic moisture and which is capillary.
Gravimetric test: BRE Digest 245 also provides specific instructions on how to determine what portion of the moisture present is capillary moisture. For this test, a wall sample is weighed, put into a humidity chamber, weighed again and then oven dried and weighed a final time. A calculation is performed using those weights so that total moisture content, hygroscopic moisture content and capillary moisture content can be determined.
Measuring moisture in floors
Concrete: According to the Concrete Society, the preferred test for determining concrete floor moisture is the insulated hygrometer test specified in BS 8203:2001+A1:2009, Code of practice for installation of resilient floor coverings. Rather than measuring the moisture within the floor, this test measures the amount of moisture leaving the floor, i.e. the moisture that can adversely affect a building’s interior and environment by increasing interior humidity and heightening the risk of condensation forming.
Further Reading:Building Research Establishment (BRE) BR466 – Understanding Dampness Building Research Establishment (BRE) Good Repair Guide 6 – Treating Rising Damp in Houses – January 1997 BRE Digest 245 – Rising Damp Treatment in Walls: Diagnosis and Treatment – January 1981 RICS Books (p.151) – Remedying Damp – by Ralf Burkinshaw Building Research Advisory Service – Technical Information Leaflet TIL 47 – August 1982 Estates Gazette – Understanding Housing Defects – 1998 BRE Good Repair Guide 5 – Diagnosing the Causes of Dampness – January 1997 English Heritage – The Repair of Historic Buildings – by Christopher Brereton
