ABSTRACT
This chapter addresses the problems caused by moisture in buildings. It examines the key ways in which this, the most dangerous of all catalysts in buildings, can cause trouble.
The special position of moisture as the principal agent causing deterioration was mentioned in Chapter 6. Moisture, of course, cannot be totally excluded from buildings. It’s needed for both the building itself and for the comfort of its occupants. Organic materials such as timber devoid of moisture would be affected by desiccation. This in turn would cause them to shrink, crack and warp. The occupants, too, cannot inhabit a totally dry building (i.e. one in which the relatively humidity is near or at 0%). Excessively dry conditions would make the occupants’ nose, eyes and mouth parched and thus uncomfortable, increasing their risk of coughing and suffering from ear, nose and throat problems. The risk of electrostatic shocks increases dramatically if the relative humidity of the indoor air goes below 30 per cent (see BSI 1991b). Too much moisture (i.e. >70% rh) in a building can be damaging not
only to its structure, fabric and contents but also to its occupants. The risks to health associated with dampness are well established (Douglas 2006; Howieson 2005). A knowledge of the main sources of moisture therefore is vital (see
Trotman et al. 2004). It will enable steps to be planned to minimise the total amounts trapped, entering or generated in a building, and so help reduce or prevent some of its detrimental influences (Rose 2005).
