How should chimneys be anchored according to structural guidelines?

Chimneys should be tied to four rafters or floor joists to ensure structural stability and to resist the forces that may act upon them, such as wind loads and seismic activity. This method of anchoring provides a solid connection that can distribute the loads effectively, preventing cracking or detachment from the building structure.

Connecting the chimney to multiple structural elements, such as rafters or joists, allows for greater resistance against movement and potential failure, especially in areas prone to strong winds or earthquakes. This requirement aligns with best practices and building codes that focus on the safe design and installation of chimney systems.

The other options do not adequately address the need for stability and performance. Anchoring solely to the roof deck does not provide sufficient support for the vertical load of the chimney. Securing with braces only may not ensure proper alignment or load distribution. Connecting the chimney directly to the foundation does not consider the necessary design for structural support through the building framing above, where the weight and forces mainly act. By tying a chimney to multiple framing members, it maintains a secure connection throughout its height, promoting overall safety and durability.