Design for Differential Movement in Brick Walls

Varying dimensional instability of juxtaposed building materials in the presence of changing heat, moisture, and stress cause differential strains, inducing stresses that frequently exceed the ultimate strength of materials. Differential strains in masonry building elements are typically of such magnitude that stress relief is more practical than resistance. Bond breaks and expansion joints are used to prevent excessive stress. Methods are presented for determining moisture and thermal movements in brick masonry, allowable deflections in brick masonry walls, and the magnitude of differential strains between brick masonry and concrete. Design of expansion joints is examined. Details are given for flexible anchorage of slabs to walls and walls to frames. Failures resulting from inadequate design for differential movement are illustrated.