Mycology & Mould Treatment

Mycology

The fungi which we are most concerned in avoiding the fabric of buildings are mould fungi, not yeast fungi. The level of moisture at which development of fungi takes place begins at around 65%, expressed as relative humidity. At higher humidities secondary and tertiary colonisers develop. The environment in which we live is not sterile and fungal spores exist at a background level at all times. A problem is deemed to exist when the concentration of fungi inside the building is significantly higher than that outside.

The simplest tests are visual and olfactory ie sight and smell tests. Further tests to identify the type of mould are possible and personal protection equipment should be utilised as a sensible precaution on initial investigation. Some fungi irritate the nose and can cause allergies.

In very wet buildings fungi such as Stachybotrys sp can develop particularly in insulator foams and Stachybotrys chartarum is an example of fungi which can produce mycotoxins with spores which can be harmful when inhaled. Not all fungi produce mycotoxins and then only in the right conditions. The level of exposure needs to be considered and as operatives dealing with damp problems the potential for harmful levels of exposure make it advisable to use respiratory protection. More information on this particular fungus is available on www.doctorfungus.org/Thefungi/Stachybotrys.php

By bringing the relative humidity within the water damaged area down below 60% as quickly as possible by shortening the drying time the growth of fungi will be inhibited.

Control of Substances Hazardous to Health (COSHH) Regulations apply to these risks and risk assessment needs to include ingestion, inhalation and contact with moulds.

A sensible strategy rather than spend too much time identifying the particular type of mould, which itself can take time, is to treat all fungi with respect and quickly return the interior of buildings to a clean, dry, mould free condition as quickly as is practical. Insurers will expect to have confirmation from a specialist that the building has been returned to it's original condition in respect of dryness and being free of mould and fungus spores before repairs are authorised.

Mould Damage

As well as unsightly staining, odours and the release of potentially harmful spores structural damage can result, such as rotting of wood and deterioration in plasterboard, wallpaper and other cellulosic materials. The damage will be minimised by prompt action to stop mould growth.

Inspection techniques

Inspection can be based on visible indicators and odour alone but in more serious cases of water damage it will be necessary to carry out more invasive testing. This will be particularly relevant where prompt action has not taken place and a period of days has elapsed since initial water damage. Removal of linings and exploratory drilling in sample locations may be necessary to establish the extent of water damage and the mould growth which will need to be treated.

Measuring and monitoring the progress of drying the area is essential for insured repairs and will be more reliable through invasive techniques than relying solely on surface measurement. Typically access into cavities and under floors is needed. Access to treat and eliminate further mould growth behind linings and in inaccessible locations will also require invasive methods. This is, however, essential if refurbishment work is to be entirely effective.

Treatment of mould

It is common for mould to develop in many buildings due to construction and ventilation issues which lead to condensation on walls and window frames. This is a particular problem where the construction includes cold bridging and hence cold internal surfaces onto which moisture will condense. Routine housekeeping measures by the building occupier will include reducing moisture production inside the property, increasing ventilation, use of fungicidal wash and redecoration with specialist paints.

Where flooding has occurred and resulted in fungal growth the aim is somewhat different. To minimise damage and prevent harm to people firstly, the spread of the problem needs to be controlled. Secondly, the cause of high humidity and ideal conditions for growth need to be addressed by building drying. Thirdly, the mould growth which has occurred needs to be treated, before reinstatement.

It is important to make an assessment of the extent of necessary work at the outset and to make photographic records of the observations. Where insurance is involved permission should be sought before commencing any invasive work which might, at a later date be seen as adding to the cost of repair.

In making this assessment it will also be important to determine the level of contamination of the area. This can range from 1 sq mt of mould caused by mains water damage, which might be treated by a simple housekeeping approach through to serious contamination requiring full isolation of the affected area with HEPA filtered indoor air and negative pressure methods. Where contamination is more serious, potential risks must be identified and risk assessments completed along with method statements to ensure that the work is completed safely.

Areas affected by mould growth and adjacent areas which may be contaminated by spores will need to be washed down using an appropriate agent. A competent technician will decide whether washing with mild detergent is adequate or specific biocides, bleach or other methods are appropriate. Consideration will clearly need to be given to the effect on the material undergoing cleaning.

The method of cleaning will vary on the different surfaces affected.