Tech Note #03 Preventing Mould Growth in Low Cost Housing

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Walling Requirements of Low Cost Housing in the Southern Cape Condensation Problem Area and the Need to Prevent Mould Growth

Introduction to problems around walling in the SCCPA

The Southern Cape Condensation Problem Area (SCCPA) is that area stretching from Malmesbury and Ceres in the West and following South of the coastal mountain ranges and escarpment though the Western Cape Province into the Eastern Cape Province and up to and including Port Alfred in the East (See Annexure C). This area is prone to prolonged periods of cold and rainy weather.

Building elements (particularly concrete block walls and fibre-cement roofs) are likely to become waterlogged by rain ingress and interior surface condensation to the extent that it may be possible that mould growth occurs on the damp surfaces. Respiratory health problems, including TB, have been reported and connected to the prevalence of such mould growth, and the associated airborne spores carried in homes in this region.

A further issue is the health risk resulting from the poor state of repair and inadequate design of much low cost housing in the Western Cape. This is reported to the Human Settlements Portfolio Committee of the Cape Town Metropolitan Council dated August 2011.

Condensation Risk in Relations to Walls

The TEMMI report to the Agrément Board of South Africa ‘Defining new condensation boundaries in the Southern Cape’ concludes that the major condensation within the low cost housing is that which is occurring on the underside of roofs, and that the condensation occurring on walls is relatively minor. The report states that the main areas in houses where mould occurs are those areas adjacent to taps, leaking pipes in kitchens and bathrooms, and around cracks in the walls. Mould is reportedly not found under-roof, and not often on walls. The mould growth in walls will be a result of structural cracks and consequent rain penetration, in the view of the authors.

From these and other comments it might be presumed that the condensation is occurring preferentially on the underside of the roofs, and that which may be occurring on the walls is within the interstitial wall cavities and is not visible.

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