Fuzzy signatures have been successfully used for various engineering applications including the strength and condition assessment of structural materials. In this paper, fuzzy signatures were used to determine the compressive strength of masonry based on groups of related measured values. Handling the uncertainty this way seemed useful because of the subjective parts and influencing noise factors of the measurements which are incorporated as leaves in the signature. For such modeling the structure from where the algebraic framework can be obtained which allows making computations with the fuzzy signatures thus determined. Since multiplicative type aggregations are applied on the various material test results assigned to the leaves of the signatures for the determination of the compressive strength of masonry, fuzzy arithmetic multiplication based on Zadeh’s extension principle was applied here. To perform the fuzzy signature calculations, the scalar product and the n-th root of fuzzy numbers were used.