Which usually requires a higher ratio of engines to structures?

• A. Interface
• B. Intermix
• C. Both
• D. None

Answer: (B)

In WUI resource planning, how structures are laid out determines how many engines you need per building. In an intermix layout, homes are dispersed throughout the fuel, often isolated from one another. That means each structure faces embers and ignition threats more independently, so you typically assign more engines to protect individual properties and quickly establish defensible space around each one. In contrast, an interface layout has houses clustered near the wildland edge, where a smaller number of engines can protect multiple structures more efficiently through coordinated defense lines, shared access, and quicker defense of the overall boundary. Because of this dispersed, per-structure protection need, intermix usually requires a higher ratio of engines to structures.