Rising Damp Advice: Rising Damp The Facts – From the Rising Damp Specialists Timberwise
2 April 2009
Meet “The Expert” This man of mystery is an experienced surveyor with a wealth of knowledge to share. “The Expert” now turns his attention to Rising Damp and looks in detail at how rising damp occurs and how modern damp proofing methods can control it.
Does rising damp exist?
Reading certain articles in a number of newspapers one would think not – it is a myth! Unfortunately the journalists have failed to appreciate the extensive research over many years into rising damp by the Building Research Establishment, the recognised testing and research authority, and other such authorities which clearly show rising damp does exist, and there are easily applicable diagnostic techniques to identify this particular form of dampness.
So what is rising damp?
It is the rise of water up through walls, the water originating from ground water: basically the wall acts like a wick.
How does it occur?
Simply think of ‘suction’ – if the suction of the wall is greater than the suction of the ground then water will rise to a greater or lesser extent. If the suction of the ground, however, is greater than the wall then water will not rise, whether a damp proof course is present or not. Once rising damp occurs, depending on the ‘suction’, it can rise to above 2 metres. However, one more commonly expects around 1200 mm and less.
What problems does rising damp cause?
Rising water causes problems of decorative spoiling and especially rot in skirtings, floor joists, floorboards and wall plates where present. Significantly, ground water salts will be deposited within the masonry and the surfaces especially plasters and decorative finishes. Most ground water only contains very small quantities of salts at levels which are generally at an acceptable level. However, as the water rises within the wall these salts are carried up into the wall and left behind as the water evaporates. Over, say, periods in excess of 50 years the continual water rise and evaporation cause these salts to build up to quite significant quantities. And here is where a further problem with long term rising damp occurs. A proportion of the salts are hygroscopic. This means that they can absorb water from the air. In some cases these salts are concentrated to such levels that sufficient water is absorbed from the air to cause contaminated finishes to appear damp. This will cause future problems in that if the rising damp is stopped, materials may still remain damp solely due to the hygroscopic nature of the contaminated material. Any decorative finish applied to such contaminated substrates would almost certainly spoil with time.
How is rising damp controlled?
To effect a dry, non-spoiling decorative surface free from water and salt contamination the control of rising damp has to be a two-part process. There is no other way!
Part 1- The injection of a damp proof course to control the rising water. A number of systems are available for this purpose, most being chemical injection systems. Most control the rising water by forming a water repellent barrier at the base of the wall thereby controlling the rise of water: some provide a pore blocking action to control rise. Chemical injection systems, and their installation are covered in British standard 6576:2005 ‘Code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp-proof courses’ ‘.
Part 2 – the removal and replacement of potentially salt contaminated plasters and finishes. This is undertaken to form a long-uncontaminated surface, and prevent any residual moisture/salts causing future spoiling. The importance of the removal of the old plaster and the reinstatement with new plaster cannot be understated.
Diagnosing dampness in buildings
Prior to introducing any water control methods it is vital to correctly diagnose the actual source of dampness. Is it rising damp, condensation, penetrating damp, or simple floor/wall junction bridging? Get the diagnosis wrong and remediation is likely to be wrongly specified. Dampness will then persist, and costs incurred in treating the ‘wrong’ dampness will be totally wasted.
It is therefore essential that the specialist damp surveyor has the knowledge, experience and appropriate instrumentation to clearly identify the different causes of dampness. We at Timberwise have that expertise and decades of experience. Our surveyors are trained in the nationally recognised qualifications, the Certificated Surveyor in Remedial Treatment. Whatever the cause of dampness, our damp surveyors will recommend the most cost effective action. We give our clients, large or small, full confidence in both the diagnosis and solution of the damp proofing problem.
For more advice on rising damp please contact the damp specialists Timberwise on o800 288 8660. We offer a range of damp proofing solutions from electro osmotic systems through to the latest in injection waterproofing.