Damp & Mould

A prospective purchaser instructed Rob Kenny of Kenny Relf Surveyors to investigate damp-related defects identified within a two-bedroom ground-floor flat in Fishbourne, near Chichester.

Areas of peeling decoration and apparent dampness had been noted around external walls, window reveals and other low-level surfaces. Understandably, there was concern that the property might be affected by rising damp or rainwater penetrating through the external walls.

Our investigation found a different and considerably more manageable cause.

The property was a two-bedroom ground-floor flat understood to have been constructed in approximately 1987. It had cavity masonry external walls with facing brickwork, a solid concrete floor, older uPVC double-glazed windows and gas-fired heating. 

The combination of limited wall insulation, older windows and a solid ground floor meant that some internal surfaces were colder than others. Particular areas of potential heat loss included the window reveals, external wall and floor junctions, and locations close to vents and other construction details.

These colder areas are commonly known as thermal bridges. They are more susceptible to surface condensation when warm, moisture-laden air circulates within the dwelling.

Peeling paintwork and other surface deterioration were visible in several areas. The damage was concentrated mainly:

• At low level on external walls
• Around window reveals
• At the sides of window openings
• At the ends of internal window boards
• In areas where furniture appeared to have previously stood

The location and distribution of the damage provided important clues. Marks on the carpets indicated that furniture had been placed against several of the affected walls, potentially restricting airflow and allowing the surfaces behind it to remain cold.

The inspection considered possible sources of moisture both inside and outside the flat.

Externally, the walls, pointing, damp-proof course, ground levels, rainwater arrangements and seals around the windows were examined. No significant external defect was found that would adequately explain the internal pattern of dampness, although some deterioration was identified in the mastic seals around the windows. The external ground levels remained below the damp-proof course and there was no visible evidence of retrofitted cavity wall insulation. 

Internally, moisture readings were taken at the affected locations using a non-invasive moisture meter. Testing was undertaken at differing depths to help distinguish moisture concentrated at the surface from moisture held deeper within the wall construction. 

The readings recorded medium dampness at shallow depths, while the wall construction behind remained comparatively dry. This pattern was inconsistent with moisture penetrating through the wall or rising from the ground. Instead, it indicated that moisture was accumulating at the internal surface.

The bathroom extractor fan operated, but its airflow was very limited. The kitchen cooker hood did not appear to discharge externally, and the windows did not incorporate trickle vents. 

Everyday activities such as showering, cooking and drying clothes introduce water vapour into the home. Without adequate extraction and background ventilation, this moisture remains within the internal air.

When warm, humid air reaches a sufficiently cold wall, floor junction or window reveal, it may cool below its dew point. Water vapour then condenses on the surface. Repeated condensation can cause staining, peeling paintwork and mould growth, particularly behind furniture or in other places with restricted air circulation.

We found no evidence of a serious structural damp problem, such as rising damp or significant penetrating damp.

The location of the affected areas, shallow moisture readings, limited ventilation, uninsulated or poorly insulated construction details and evidence of furniture against the walls all supported condensation as the principal cause. 

The purchaser was reassured that the findings did not indicate a hidden or extensive structural moisture problem. The defects were considered consistent with the age, construction and ventilation arrangements of the flat and capable of being substantially reduced through appropriate improvements.

We advised that the property should be approached using a coordinated moisture-management strategy rather than conventional damp-proofing treatments.

The initial priorities were to:

• Upgrade the bathroom extractor fan, associated ductwork and external outlet
• Provide effective mechanical extraction from the kitchen to the outside
• Replace deteriorated external mastic seals around the windows
• Maintain suitable background heating
• Avoid positioning large items of furniture tightly against cold external walls
• Improve air circulation around window reveals and external wall junctions

Further improvements for consideration included installing a Positive Input Ventilation system, upgrading the older windows, using a suitable tumble dryer rather than drying clothes internally, and improving the efficiency of the heating system. 

These measures were recommended as part of an overall strategy to control internal humidity and increase surface temperatures. No individual measure was presented as a guaranteed cure.

The investigation provided the purchaser with a clear explanation of the defects and a proportionate plan for addressing them.

Most importantly, it avoided the assumption that visible dampness automatically required an injected damp-proof course, waterproof render or another disruptive damp-proofing treatment. The evidence instead pointed towards condensation associated with cold surfaces, restricted airflow and inadequate extraction.

This case demonstrates why dampness should be diagnosed by considering the whole building. Moisture readings alone do not identify the cause. The construction, defect pattern, depth of moisture, ventilation, heating and use of the property must all be assessed together.

Damp patches, peeling paint and mould growth do not necessarily mean that a property needs expensive damp-proofing work.

Kenny Relf Surveyors provides independent damp and mould investigations across Chichester, Fishbourne, Selsey, Emsworth, Bognor Regis, Havant, Waterlooville, Petersfield and surrounding areas.

We do not sell damp-proofing treatments. Our role is to investigate the evidence, identify the most likely cause and provide clear, practical recommendations.

Arrange an independent damp and mould survey before committing to remedial work.