Concern & action: Rain and Drains (liquid moisture penetration)

Excess liquid moisture in fabric caused by rain and poor fabric condition (e.g. poor pointing, porous masonry, cracks), defective rain water goods, high ground levels, high water table, poor detailing (e.g. around windows, external wall insulation) or reduced ability of the fabric element to dry (due to reduced vapour openness or reduction of heat reaching the fabric).

Suggested actions

Before Implementation

Ensure property is in good state of repair prior to refurbishment. Commission a professional building surveyor (RICS) to investigate condition of fabric. If necessary repair any features that may reduce effectiveness of measure e.g. re-point wall, mend/replace downpipes, reduce ground levels and add drainage to ground around property. Careful surveying and detailing required at design stage to provide clear information with full installation details (e.g. of VCL layer if applicable).

During implementation

Ensure there is a robust delivery chain (design/supply/contractor/occupant) in place to be able to replicate the design details on site. Particularly necessary for insulation applications where mitigation of moisture risk may rely on intact VCL which should not be punctured i.e. by services, picture/shelf hanging or EWI where edge details maybe vulnerable to water penetration particularly in instances of rainwater goods failure. Ensure risks are understood by occupants. Provide targeted advice to occupants to keep a watchful eye on conditions (air quality, mould build up in bathrooms) and to seek advice if uncertain.

After implementation

After refurbishment, watch for signs of deterioration (leaky pipes, mortar loss, damp) around the building. Remember that prompts may be needed for users to check the state of repair at regular intervals. For significant and/or vulnerable fabric an early warning monitoring system measuring moisture content/relative humidity should be installed to provide regular checks on the moisture condition of fabric including an alarm system for prolonged periods in excess of 15% moisture content or 80% RH. Report results to add to knowledge about refurbishment measures (e.g. monitor wall fabric condition (heat and moisture behaviour). Reporting of results of this monitoring to wider interest groups.