Methods of Damp Proofing London

(The cost of this add-on is deducted from your repair bill if we carry out the recommended remedial works).

Small plaster samples are carefully taken from affected walls and sent to an independent laboratory to analyse the concentration of hygroscopic salts (chlorides and nitrates).

Why it matters: Hygroscopic salts are carried by ground moisture during rising damp and remain in plaster even after masonry dries.

Diagnostic value: Differentiates true rising damp from condensation, rainwater penetration, or temporary plumbing leaks.

Note: Salt analysis can be particularly helpful when moisture-meter readings alone do not provide a sufficiently clear diagnosis. It may assist in distinguishing possible rising damp from condensation, water penetration or residual contamination caused by a historic leak. 

The results are considered together with the moisture profile, construction of the building, external ground levels, condition of the damp-proof course and other survey observations. This is the only additional service requiring minor invasive work because physical plaster samples must be collected. If we undertake the recommended remedial work, the survey cost will be deducted from the cost of that work.

Surface swab or lift samples are submitted to an accredited laboratory for advanced qPCR DNA testing to identify exact mould species and spore concentrations.

Why it matters: Identifies toxigenic species (e.g., Stachybotrys chartarum) and concealed mould growth behind dry lining or furniture.

Diagnostic value: Establishes whether mould contamination is localised or widespread, enabling precise environmental remediation planning.

This service may be beneficial where:

• A persistent musty smell is present
• Mould repeatedly returns after cleaning
• The property has experienced previous water damage
• Contamination is suspected behind furniture or inside cupboards
• Occupants have concerns about the indoor environment
• The extent of visible mould is unclear
• Independent laboratory evidence is required

Note: The results can help establish whether contamination appears isolated or more widespread. They may also assist with planning appropriate cleaning, removal, drying, ventilation or moisture-control measures.

Laboratory mould testing does not replace the need to investigate the moisture source. Mould is normally a symptom of excess moisture, condensation, leakage or inadequate ventilation, so the underlying cause must also be identified. If we carry out the recommended work, the survey fee will be deducted from the cost of that work.

(The cost of this add-on is deducted from your repair bill if we carry out the recommended remedial works).
Comprehensive environmental air quality screening for properties with persistent odours, post-flood contamination, or air quality issues.

Screening includes:

• Indoor air-quality assessment – IAQ
• Volatile organic compounds – TVOC/VOC
• Formaldehyde – HCHO
• Fine airborne particles – PM1.0, PM2.5 and PM10
• Dust and smoke particles – PM1.0, PM2.5 and PM10
• Sewer gas screening – H2S, NH3 and CH4
• Flammable gas screening – CH4 and C3H8
• Carbon monoxide – CO
• Hydrogen sulphide – H2S
• Ammonia – NH3
• Oxygen levels – O2
• Stale-air and ventilation assessment – IAQ and TVOC
• Drain odour investigation – H2S, NH3 and CH4
• Chemical smell investigation – TVOC, VOC, HCHO and NH3
• Post-leak air and surface-condition checks – PM2.5 and TVOC
• Combustion gas screening – CO, O2 and CH4
• Building-product off-gassing assessment – TVOC and HCHO
• General pollutant screening – PM1.0, PM2.5, PM10 and TVOC

Diagnostic value: Pinpoints the source of foul drain odours, chemical off-gassing and stale air problems linked to poor ventilation. It is also useful when a property contains a persistent foul, stale or unexplained smell. Odours can originate from damp building materials, stagnant water, contaminated drains, sewer gases, mould-related conditions or chemical vapours. Targeted screening helps narrow down the possible source and supports further investigation.

Note: Screening results do not replace specialist gas, environmental or medical assessments where these are required. The survey charge will be deducted if London Damp Specialists completes the recommended remedial work.