A straightforward approach to the measurement of moisture in a building material is to remove a sample by drilling. The water content of the powdered sample is then determined by oven drying or with a calcium carbide meter. This article shows how this method can be improved to give an accuracy of better than ± 1 per cent moisture content. This is done by adopting a consistent or 'standardised' drilling procedure and calibrating this for the material concerned. Calibration curves are shown for three types of brick and for 1:1:6 mortar. Two calcium carbide mosture meters are tested. Both are shown to over read, giving a maximum error of about 1.5 per cent when the moisture content is 20 per cent (based on wet weight). However, this error can be reduced by calibrating the meters themselves. Experiments are described in which the drilling method was used to show the large variations in brick moisture content from place to place in a naturally exposed wall, and to measure the effect of cavity insulation on the drying of a wall.