Infrared imaging (thermography) is a valuable tool for nondestructive evaluation of thermal properties in masonry walls. For example, the technique determines whether reinforced cells are properly grouted, whether a cavity wall is filled or empty, and where moisture is entering masonry walls. The technology makes it possible to scan large areas of a structure quickly and in a continuous manner. The principle of the method is explained. IR thermography requires a temperature differential between the interior and exterior wall faces. Two types of IR surveys, qualitative and quantitative, are conducted, depending on the intended end use. IR cameras used in building surveys are considered. Two case studies of the use of IR imaging, for examining internal brick wall construction, and for locating internal voids to be filled with injectable mortar in order to extract salts from walls, are presented.