Geo-electric measurements in combination with calibration corings are used for the survey and quality control of consolidation injections in historic masonry. The geo-electric measurements, executed with an asymmetric Dchlumberger disposition, give the distribution of the resistivity over the masonry mass. By means of calibration corings the resistivity data are related to void content, porosity and composition. After injection the same procedure is used to check the grout consumption and the uniform quality of the treatment. Two prototype consolidation and control works are presented : The castle of the counts of Flanders (12th Century) and the tower of the St. Mary's Basilica at Tongeren (15th Century).