Control Joint

Definition

A control joint is an intentional linear discontinuity in a structure or component, designed to form a plane of weakness where damage or movement can occur in response to various forces, minimizing or eliminating damage elsewhere in the structure.

Purpose

The purpose of a control joint is to control the location of cracks that might occur due to shrinkage, temperature changes, or other movements, thus preventing random cracking and structural damage.

Examples of Use

• Concrete slabs have control joints to manage cracking due to shrinkage as the concrete cures.
• Masonry walls include control joints to accommodate thermal expansion and contraction.
• Sidewalks use control joints to prevent unsightly and unpredictable cracks.

Related Terms

• Expansion Joint: A joint that allows for expansion as well as contraction of building materials.
• Contraction Joint: Similar to a control joint, it specifically deals with shrinkage and contraction movements.
• Seismic Joint: A joint designed to allow independent movement of different sections of a building during an earthquake.

Notes

Proper placement and spacing of control joints are critical to their effectiveness. The joints should be deep enough to create a plane of weakness and filled with suitable materials to accommodate movement.