Have a read of this article first, it pretty much says it all...
The myth of rising damp
BYLINE: Rachel Kelly and Tom Rowland
SECTION: Features
LENGTH: 930 words
Rachel Kelly and Tom Rowland on a steamy debate
It is a frequent worry for homeowners, but is rising damp so common? A London council thinks not. Its housing officials are so confident that rising damp is more likely to be condensation or damp penetration from outside that they are offering a Pounds 50 reward to any council employee who can prove them wrong.
Mike Parrett is manager of Lewisham Borough Council's housing disrepair scheme, and a recent recipient of an award from the Institute of Maintenance and Building Management for his work on damp problems. It is not that rising damp does not exist, he says; it does, but rarely. He has handled hundreds of supposed cases of rising damp over the past decade, but has yet to install a single chemical damp course. He says: "Millions of pounds are being thrown to the wall. Chemical damp-proofing does not work. Every time my staff looked at a case of so-called rising damp, they found the problem was condensation caused by poor heating and ventilation, or penetrating damp from raised ground levels or leaking pipes.
"I have never found moisture being drawn up from foundations. The point of the reward is to convince tenants that rising damp is a myth. Every wrong diagnosis could cost us Pounds 5,000 a house, which could provide central heating and ventilation for two properties: improvements that we know will cure dampness."
The council's claims have sparked a debate within the building industry about chemical damp-proofing. Treating rising damp is estimated to cost local authorities and owner-occupiers between Pounds 100 million and Pounds 200 million a year.
Dr Chris Coggins of the British Wood Preserving and Damp-Proofing Association represents about 220 rising damp firms. He says: "Rising damp does exist and can be treated. The trouble is that frequently it is not specialists who treat the problem."
Rising damp is often misdiagnosed, say others in the building trade, who say the "remedies" may be costly, intrusive and useless.
According to the Government-funded Building Research Establishment (BRE), rising damp makes up only about 10 per cent of damp it investigates in buildings. The BRE became so worried about incorrect diagnoses that it issued a guide last year pointing out how costly, and intrusive to the fabric of houses, were the remedies, and how vital it is to rule out condensation first. Unlike rising damp, which requires the drilling of holes along entire walls so that a liquid waterproofing can be pumped in, condensation can be cured by opening a window. It may also be wise to insert an air brick or two.
Part of the reason for the concern over rising damp is that homeowners are told about its perils by house surveyors. Research by the building construction department at the University of the South Bank suggests that 75 per cent of surveyors expect to find the condition in period homes they examine.
The standard "damp test" of surveyors is to prod a wall with an electronic conductance meter. The more damp be tween the two terminals, the higher the reading will be. But the study revealed that 74 per cent of the surveyors questioned did not know these meters are calibrated for timber, not masonry. Meters tend to over-react when prodded against a brick wall and show higher levels of moisture than are present. The manufacturers of the meters recommend that further tests are carried out to confirm the diagnosis of rising damp, but few surveyors bother. Instead, terrified of the prospect of being sued for negligence, they write survey reports that recommend that the damp be investigated by a specialist.
Unfortunately, most owners and prospective buyers faced with this advice phone a firm for a free damp survey, and fail to realise that the "specialists" fielded to carry out this free service are sales staff often paid on commission for selling pumped chemical anti-damp treatments.
Better safe than sorry, you might think. But it is not clear whether these chemical damp-proofing treatments prevent damp from rising in walls. Researchers at the University of Manchester Institute of Science and Technology have warned homeowners that the treatments are not being properly used. The technique is to drill the wall with a row of holes, then pump each with damp-proofing chemicals for between ten and 20 seconds. The Manchester team concluded that to create an effective barrier, the liquid should be pumped into every hole for up to 20 minutes. If the wall is damp when the work is done, the chemical will not adhere.
The BRE says that the only way to be certain a wall has been damp-proofed is to cut out the brick work from both sides and insert a layer of slate to stop any water. But this is hugely expensive.
The installation of central heating, proper ventilation and maintenance of gutters and downpipes cures most damp problems, says the South Bank University construction technologists. They add, incidentally, that it is remarkably difficult to get water to rise through brickwork, even under laboratory conditions.
BE SURE OF THE DIAGNOSIS
WHEN rising damp is misdiagnosed, it is usually because of misuse of electrical moisture meters. Such meters are reliable for use with timber, but building materials such as brickwork often contain matter that will give very high moisture readings, even when no dampness is present. Dampness levels in masonry should be analysed by a method using calcium carbide, not by electrical moisture meters. This method of testing can be carried out on-site.....
The key issue for me has always been not that chemical DPC's aren't effective but that rising damp is extremely rare and frequently diagnosed with the use of handheld electronic moisture meters alone. More often than not chemical DPC's are installed where they're not required. As part of my dissertation I resurveyed 10 properties that had been surveyed by DPC specialists with a vested interest in selling chemical dpc's. Not one of those properties actually had a rising damp problem and i proved this by carrying out salts analysis tests and calcium carbide tests.
Chemical dpc's can be effective where rising damp is proven but they're a very hit and miss affair due to quite often poor installation standards. A lot of specialists don't even bother treating the mortar joints despite the fact that these are the major moisture pathway for rising damp. If that happens then chemical injection is a complete waste of time.
Go to:
http://www.safeguardeurope.com/applications/rising_damp.php?gclid=CKqux4rAy5ECFSPIXgod2WmWzw
and download the data sheet on rising damp and it's control. It's produced by Safeguard but actually explains very well the process of viscous fingering and why pressure injected systems are less successful. Sure this is an industry document but it follows all the academic research on the subject. It's interesting that you mention that British Board of Agrement; they've actually approved many chemical injection products on the basis that only the brick is treated, the systems appear relatively successful because the cement based renders and plasters dam in the damp. The BBA have got it wrong on a huge scale and in my opinion it's only a matter of time before all the industry moves away from treating bricks and starts treating the mortar courses.
Joe
