Which defensive strip variant is used when construction is off the purlin?

• A. A hose line
• B. Defensive Strip (LWP Roof Diagram)
• C. Defensive Strip Against Construction (Off Purlin)
• D. Defensive Strip With Construction (Off Beam)

Answer: (C)

Defensive strip variants are chosen based on how roof construction sits relative to the purlins, because that placement changes how heat and fire will travel and where a shield needs to be placed during vertical ventilation. When construction is off the purlin, the proper approach is a defensive strip against construction that’s off the purlin. This means you orient and position the strip to butt against the off-purlin construction, creating a barrier that blocks fire from sweeping around that construction and into unburned areas while you perform ventilation. The off-purlin arrangement changes the fire path and anchoring points, so placing the strip against the construction provides the needed stability and protection. Other variants address different structural relationships (such as off the beam or generic configurations) and don’t specifically account for the off-purlin scenario, which is why they aren’t the best fit here.