Our experience from site visits is that timber sills are not protected if it rains while the house is under construction. However, opinions in the building industry are divided as to whether this presents a problem in terms of risk of mould growth. This study was carried out in order to investigate whether wooden sills and studs can withstand being briefly exposed to water before they are built in by the rest of the structure, or while they are built in, and whether there is any risk of mould growth.