Mould and ventilation management

The English House Condition Survey of 1996 estimated that 15% of all households suffer mould growth on walls, ceilings, carpets or furniture. Two-thirds of mould cases are classified as slight, with the remainder moderate or severe. This could be an underestimation, as more mould may be hidden from view in ducts and voids or behind furniture.

Mould is most common in the rented sector. Problems are more widespread among older flats, terraced houses, larger households and homes without adequate central heating. However, more positively, the incidence of mould growth had fallen from a level of 17% in the 1991 House Condition Survey. The EHCS does not link ventilation in homes to incidence of mould, and it is extremely likely that the amount and type of ventilation in a home has a bearing on incidence of mould.

Mould is often linked to 'fuel poverty'. Those households that spend more than 10% of their annual income on fuel, or whose actual fuel spend falls below the required fuel cost, are usually considered to be suffering ‘fuel poverty’. Some households simply cannot afford to heat their home satisfactorily.

There are thousands of mould species. Once a suitable substrate becomes wetted/damp, moulds can colonise within less than a day. We all see how quickly moulds proliferate on foodstuffs in the home.

Mould has been with us in buildings for centuries, but over the past few decades changes in how we heat, ventilate and insulate buildings have, according to most commentators, produced conditions more and more favourable for them.

Mould is a symptom of a damp problem, but unusually this symptom itself can be a threat to health.

Surveyors have been referred to as 'property doctors', but surely we cannot be expected to be medical doctors too? But if we survey occupied property, where we see occupiers suffering symptoms commonly associated with bad air, and more specifically mould contamination, could we be held accountable for failing to see the link between human health and building condition? So listen more carefully for that tell-tale cough, or a child using an asthma pump.

Research into mould and the implications for chartered surveyors

An RICS report on mould was published in 2005 entitled Research into mould and the implications for chartered surveyors. The word 'toxic mould' was deemed in this report to be a misnomer, although the report did not clearly explain why. It may be because research has not yet been produced to conclusively link particular moulds to certain illnesses or health symptoms. The author has come across a number of mould experts (mycologists) who recoil from the term 'toxic mould'.

In preparation of that research paper, 1,200 properties were surveyed. Mould was most commonly found in bedrooms, then bathrooms and kitchens. Forty per cent of mould contamination was discovered in bedrooms. It is usual for moisture to be heavily generated in bathrooms and kitchens, by cooking or washing, then condense there, or on cold surfaces in another room – even far removed – perhaps a poorly heated spare bedroom. Living rooms exhibited the least mould development (only 3% of identified mould).

No information was published on the types of residential unit surveyed, ages of buildings, tenure, etc. but it was clear that mould can derive from penetrating damp very commonly (28% of cases) as well as condensation (58%). Damp penetration can promote condensation, as wet building fabric becomes a cold bridge.

The surveys carried out included taking mould samples for laboratory analysis.

It is not always easy to identify species, and sometimes the precise identification may be of limited practical use as we know so little concerning the risk to health of the many thousands of mould species. However, we do have knowledge of certain species, and if species proven to be a health risk are identified, we will know just how carefully the mould colonisation will need to be dealt with. Some experts suggest that the species is not the key factor concerning the risk to health, but the amount of mould. 

In the USA, some extremely high-profile court settlements concerning mould, which have run into millions of dollars, make all those involved in designing or surveying buildings on this side of the pond rather edgy concerning potential future claims.

Key lessons learned from such cases include:

• Take early professional advice when musty smells are noticed.
• Consider advising tests of plumbing in survey reports.
• Be alert to typical illness symptoms associated with exposure to moulds.
• Remember that mould can develop extensively out of view, so consider opening up when surface symptoms of mould or damp appear.
• If you suspect hidden mould may be present, advise further investigation.