On a slope, which combination supports effective defense for a WUI structure?

• A. Increase defensible space only
• B. Increase defensible space and structural hardening on slope
• C. Rely only on suppression access
• D. Ignore slope effects

Answer: (B)

On a slope, fire behavior changes: uphill fire spreads faster, flames and embers are carried more readily upslope, and radiant heat can reach the structure sooner. That means two layers of protection work together best. Increasing defensible space around the home reduces nearby fuels, slows and interrupts flame contact, and helps keep embers from starting a fire on a treffen point or around vents. Structural hardening on the slope makes the building itself more resistant to ignition from radiant heat, embers, and sparks—think ember-resistant vents, noncombustible roofing and siding, sealed gaps, and proper clearance of nearby fuels.

Relying only on suppression access doesn’t reduce the chance of the structure catching fire, and ignoring slope effects leaves the building vulnerable to rapid uphill fire spread and ember exposure. So combining a clear defensible space with hardened construction provides multiple, complementary defenses that are especially important on sloped terrain.