Mould Remediation in East Sussex for Hove Lets

The Brief

The homeowner of an HMO property based in Hove contacted us to carry out air sampling as they were concerned about mould growth in several rooms.

Fully refurbished, the East Sussex property has been converted into six bedrooms, with the three ground floor bedrooms fitted with ensuites. It was these three bedrooms which were experiencing mould growth, and were in need of black mould removal.

The Objectives

Air samples were taken in the three affected bedrooms, as well as in the downstairs hallway. Samples were also taken from outside to compare results against; remember, a professional mould removal is about reducing spore count, not complete eradication. There will always be mould spores within the air and that is completely natural. It’s practically impossible to completely get rid of them all. However, the indoor spore count shouldn’t be higher than that outside.

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The affected property is approximately 100 years old and is an end of terrace. It has been converted into six bedrooms and fully refurbished. The three bedrooms on the ground floor are fitted with ensuites, and all suffering from mould growth.

The exterior wall that runs down the side of the property has been treated for damp penetration, however, the front and rear walls look in good condition and show no signs of water penetration.

The Technical Part

The moisture readings taken in the three bedrooms were non-invasive but indicated that there was trapped moisture within the fabric of the building – in particular in bedrooms one and three.

Bedroom two also provided a high REL reading, indicating high moisture levels within that room. However, this was most likely due to surface moisture generated from a lack of airflow and ventilation.


Location Relative Humidity Dewpoint
Exterior 69.1% 9.6 deg
Bedroom One 82.8% 15.3 deg
Bedroom Two 70.6% 15.4 deg
Bedroom Three 63.6% 21.8 deg

NB: A normal relative humidity range is between 40 – 50%.

Bedroom One:
The isolation switch for the extractor fan in the ensuite of bedroom one was found to be switched off, contributing to the trapped moisture in the bedroom. The windows also had no trickle vents to allow for natural ventilation.

Additionally, there was an area of damp on the external wall, which has the drain point for rainwater outside. This damp could potentially be rising up the wall and penetrating into the bedroom. The external work that was carried out may also have trapped moisture into the wall, which is now evaporating into the bedroom.

The internal area by the drain point outside was showing evidence of peeling paper and cracks which are often signs of a damp issue. There was also mould present at low level along the external wall.

Bedroom Two:
Although there were no obvious signs of an escape of water, mould was present in the corner of the bedroom which backs onto the shower of bedroom three. However, the moisture readings taken on the wall did show signs of trapped moisture.

The isolation switch for the extractor fan for the shower in bedroom two was turned off, subsequently contributing to the trapped moisture in the bedroom.

In the corner where the mould was seen to be growing, a chest of drawers is usually pushed up against the corner. This could also be contributing to the mould growth by reducing airflow and ventilation in the room.

Bedroom Three:
There was an obvious sign of mould growth on the lower section of the external wall that is the end-of-terrace wall. This wall had remedial work completed to the exterior to prevent damp ingress and it is likely that water became trapped within the wall, with the only escape being into the bedroom.

The bedroom had the isolation switch for the extractor fan turned on, and the windows were open to allow good ventilation to the room. However, there was still mould growth on the wall which shows that even with the preventative measures taken, there was still excess moisture in the air (confirmed by a reading of 63.6% RH).

Mould Remedial Recommendations

To combat the microbial growth, we recommended a thorough decontamination of the affected areas to kill off any mould spores on the surfaces. The decontamination process included the cleaning of the contaminated surfaces by hand with suitable remediation products, followed by fogging of the bedrooms to eradicate any airborne spores.

Following the mould removal Brighton process, bedrooms one and three required target drying to the affected areas with dehumidifiers and tenting off the immediate areas. This process would take two weeks to complete.

The affected areas in these bedrooms needed drying to remove the excess moisture – the number one contributing factor to mould growth. The aim of the drying process was to reduce the relative humidity to within normal range, which lays between 40-50%. If we had not completed thorough drying of the rooms, the mould would be highly likely to return due to the elevated levels of moisture.

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