Rising Damp Control
Rising Damp Control
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 rising damp control solutions & systems used by damp-proof specialists, such as an injected damp-proof course, a physical damp-course & the electrical lectros electro-osmosis damp-proofing system which is ideal 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.
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.
Rising Damp Symptoms
Rising damp is fairly slow to develop and may be present for several years before any symptoms become apparent. Eventually it may show as a tide-like damp stain on the wall 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.
Rising Damp Surveys & reports for mortgage providers where a damp inspection has flagged up dampness on a home buyers valuation survey & for home owners applying for loans from equity release companies.
Before considering the installation of a chemical damp-proof course to cure rising damp, the Damp Aid 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 Damp Aid 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.
Mis-diagnosis of “Rising Damp”
We are often asked to inspect properties which have been reported to have “rising damp” (usually stated in a homebuyers report that the walls are showing signs of damp). More often than not it is found that the wall plaster is in contact with a solid floor, therefore “bridging”. Residual moisture in the floor is drawn up into the wall plaster by the wick effect resulting in high damp meter readings during surveys or sometimes even damp staining. The removal of the defective wall plaster is all that is required, ensuring new plaster is not in contact with the floor.
Moisture meters, used to test walls for damp, do not really measure moisture content in walls They measure electrical conductance, and will give a high meter reading on any material which allows an electrical current to flow through it. When testing for damp, care should be exercised to ensure that there is no interference from certain materials. Foil under wall paper (was commonly used to help combat condensation) and clinker blocks (made from coal ash with a high carbon content) will always cause very high readings even if the wall is in fact bone dry.
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 control method of installing a damp-proof course in a house.
Cost of Treating & How toTreat Rising Damp 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.
Treatments & Rising Damp 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 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.
Electrical Osmotic damp-proof course system (Electro-Osmosis). 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 damp-proofing 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.
Building Research Establishment (BRE) Good Repair Guide 6 – Treating Rising Damp in Houses – January 1997
BRE Digest 245 – Rising Damp 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
Birmingham, Cheshire, Chester, Wrexham, Lancashire, Liverpool, London, Manchester,
Merseyside, Middlesex, North Wales, Shropshire, South East England, West Midlands, Wirral & Yorkshire