Penetrating or rising dampness

Tony Jackson is an MRICS chartered building surveyor with no links to any damp associations or damp remediation companies. Instead of making assumptions about damp findings which justify a certain type of remedial work, Tony is able to diagnose the cause of dampness using both non-destructive methodologies, and where necessary, destructive testing. Tony has spent many years working as an Expert Witness, either proving or ruling out dampness within structures using methods such as calcium carbide testing which satisfy a court of law.

During the course of hundreds of Expert Witness inspections, Tony has on a small number of occasions diagnosed true rising dampness in residential properties, and in these cases damp proofing contractors would likely suitably resolve these issues. However, it has been observed that their method of diagnosis often does not involve the industry-accepted methods of establishing whether dampness is present within the wall at depth (calcium carbide testing of drilled samples), establishing whether such dampness originated in the ground (ground salt analysis). or establishing whether hygroscopic salts are present (gravimetric testing of drilled samples, or ground salt analysis). True rising dampness is rarely the cause of damp findings. It should also be noted that mould growth is usually caused by surface condensation. Rising damp generally does not result in mould growth due to the mould-inhibitive nature of ground salts.

A reputable and knowledgable builder may be able to correctly diagnose the source of moisture and carry out appropriate repair work which alleviates the source of dampness rather than merely masking the dampness or making matters worse.  It should be borne in mind, however, that repair works are often observed in the course of surveys which, due to an incorrect diagnosis, can make the problem worse, or be unnecessarily extensive and costly for the client. An example which is regularly encountered is attempting to prevent dampness penetrating into a porous, solid wall by repointing with a cement-based mortar. This impermeable mortar traps moisture within the wall, often making internal dampness worse, as well as causing the external surface of the masonry to spall and delaminate - a defect which can be impossible to satisfactorily rectify and reduce the value of a property. 

A damp meter (electronic moisture meter) is a useful diagnostic tool during the initial stages of an inspection, and will usually be used, possibly along with thermal imaging, to indicate areas of potential dampness which require further investigation with either deep probe testing, ground salt analysis or calcium carbide testing of drilled samples. Damp meters themselves work on electrical conductivity and are calibrated for the moisture content of timber. Their readings are affected by things such as foil, residual salts and black ash mortar. As such, damp meters themselves cannot be relied upon to confirm dampness.

A thermal imaging camera is often used as a useful indicator of the variability of surface temperatures, revealing relatively cooler surfaces which may be prone to surface condensation and consequential mould growth. They do not indicate dampness itself however, and the presence and type of dampness can only be confirmed using the methods described above (ground salts analysis, calcium carbide testing or deep probe testing) or by diagnosing condensation using psychometric readings and infra-red surface temperature testing.

Chartered surveyors undertaking RICS Home Surveys have a very wide breadth of knowledge encompassing gas, electrics, water, heating, plumbing, ventilation, building regulation compliance, fire safety, building defects of all kinds and various types of statutory compliance. The majority of these surveyors are not specialists in damp diagnosis, and carrying out such diagnosis would involve obtaining permission to disturb wall plaster, take an unfeasibly long time, and potentially open the surveyor up for claims of professional negligence. Some home surveyors offer a follow-up damp diagnosis service, but such a service involves an investment in some expensive equipment (particularly the 'Speedy' meter), and in any case, many surveyor's diaries do not have gaps in which to book such a service. Home surveyors' damp diagnosis equipment is often therefore limited to a damp meter (electronic moisture meter). It has been noted that some surveyors interpret damp meter elevated readings (on walls with no signs of dampness) as dampness within the structure which requires further investigation. Recommending further investigations is sound advice, but rather than stating that damp meter readings have detected dampness, it would be more accurate to state that damp meter readings are often misleading, and further investigations should be undertaken to either confirm or rule out dampness within the the structure.

Fees are dependant on the age, type and location of properties and extent of issues. In more complex cases, surveys can be carried out in stages. Please contact us for an informal discussion about your requirements.