Purpose Material properties, such as shear and compressive strength of masonry, have a crucial impact on the seismic analysis results of masonry structures. Considering that most of the historical buildings are masonry structures, the damage caused by obtaining shear strengths with known methods exceeds acceptable limits. Instead of traditional shear strength index tests, this paper presents a test technique that has been developed which causes less damage to the structure, to obtain mechanical properties in masonry structures. Design/methodology/approach A new approach to shear testing and a test probe has been developed to minimize the destructive effects of mechanical in situ testing on masonry structures. The comparison of the results obtained with reduced destruction level using the novel shear strength index test probe with those obtained from the traditional method is addressed. Masonry specimens were tested in the laboratory and in situ tests were carried out on 12 historical buildings. Findings Test results obtained from the proposed probe shear strength index test were consistent with the results obtained from the conventional shear strength test both at the laboratory setting and in situ. Although a large number of data is needed for the validation of a method, satisfactory agreement with the conventional shear strength index test method was obtained. Originality/value The authors believe that the proposed method would give the opportunity to collect more mechanical strength data with much less destruction. The experimental work in the laboratory and in situ tests and their comparisons are the supportive and original values of this research.