We may think of the building envelope as an inanimate object, but in reality its components can be quite mobile. Building materials grow, shrink, shift, bulge, deform, and elongate in response to stresses and fluctuations in the environment, and these dimensional changes often impose strain on adjacent elements. Where the forces of movement are not foreseen during design and construction, evidence of the struggle will emerge, in the form of cracks, spalls, displacement, broken glass, warped metal, and, eventually, breakdown of the assembly.
IDENTIFY causes of dimensional changes in building envelope elements.
DESCRIBE strategies for accommodating movement in the building enclosure.
DISTINGUISH among types of movement joints, including construction joints, control joints, and expansion joints.
EXPLAIN the effects of differential movement in building envelope materials and discuss methods for permitting independent movement.