Which statement about movement at isolation joints is true?

Which statement about movement at isolation joints is true?

• A. They permit both horizontal and vertical movement.
• B. They permit vertical movement only.
• C. They are rigid and immobile.
• D. They permit horizontal movement only.

Answer: (A)

Isolation joints are placed to separate concrete members so they can move independently without transferring stresses across the joint. The joint is filled with a flexible material so the two sides can slide and move as needed. Because temperature changes, shrinkage, and settlement can cause movement in multiple directions, isolation joints are designed to permit movement in both horizontal and vertical directions. If movement were restrained, cracks and related damage would occur as the concrete expands, contracts, or settles. So, the statement that movement is allowed in both directions best describes how isolation joints function.

Isolation joints are placed to separate concrete members so they can move independently without transferring stresses across the joint. The joint is filled with a flexible material so the two sides can slide and move as needed. Because temperature changes, shrinkage, and settlement can cause movement in multiple directions, isolation joints are designed to permit movement in both horizontal and vertical directions. If movement were restrained, cracks and related damage would occur as the concrete expands, contracts, or settles. So, the statement that movement is allowed in both directions best describes how isolation joints function.