Monitoring moisture condition

House surveyors have advised monitoring in survey reports for many years (for cracks to determine if a building is still on the move). We can do the same for dampness. Monitoring includes observation and recording of all manner of events inside and outside a building, not just measuring moisture condition. Monitoring can help in a diagnosis or help evaluate a remedy.

Do not be under the false impression that monitoring necessitates complex set-ups of sensors, wires and probes linked to unfathomable computer software. Though there are experts in the industry who are able to monitor building performance using all manner of sophisticated techniques, the aim of this section is to advise the working house surveyor on techniques that are practical and useful.

This section introduces a way of categorising monitoring into 5 levels. It then shows a series of moisture measuring tests undertaken by the author using various types of moisture measuring equipment, and takes you through some examples of monitoring to demonstrate how monitoring data might be interpreted.

Many property inspections are single-visit inspections, snapshots of the building – so there is no opportunity to observe moisture conditions over time, to find out if dampness is regressive, unchanged or progressive. For house surveyors, monitoring could be useful for a number of reasons:

• To assess the influence of use and occupation.
• To help evaluate the influence of weather on dampness or wetness.
• To determine any defects or inherent construction problems.
• To evaluate any design issues and or materials used.
• To assess the impact of damp-proofing or waterproofing on the internal environment.
• To appraise the effect of a new ventilation scheme.

Sometimes you will need to think outside the box; for example, when an occupier might innocently water plants or clean a floor, wetting areas of the building being monitored during the drying process after a flood.

Two sectors of the property industry have been taking monitoring very seriously for some years:

• the flooring industry; and
• the damage management industry.

The procedure for checking the dryness of screeds is laid down in BS 8203. Later in the section we show you how surveying instruments can help you check this yourself.

Damage management contractors dry buildings after all manner of flood events. Low surface moisture meter readings from an electronic moisture meter alone are not usually sufficient evidence of dryness to convince them to switch off dehumidifiers and leave the site. If they have failed to monitor drying carefully enough and the walls and floors are still in fact damp at depth, then decorations and finishes will be ruined a second time around by the still lingering underlying dampness.

In the context of a dampness investigation, checks are made of the moisture condition of air, solid porous materials, and air within solid porous materials or trapped over a substrate.

Using standard survey equipment, measurements are taken of the following to help us understand change in moisture condition:

• air temperature;
• humidity;
• conductance; and
  
• capacitance.