WUI Addition With a Wood Shake Roof
A homeowner in a high fire hazard severity zone proposes a 1,200 sq ft addition to a 2,000 sq ft single-family home. The existing roof is 25-year-old wood shake; the addition will have wood siding, an unenclosed deck, and standard soffit vents. The lot is on a 25% slope, with 15 ft to a dense stand of juniper and pine. The private road is 16 ft wide, and the nearest hydrant is 1,100 ft away. The homeowner argues the roof is existing and only the addition should be reviewed, and that the project is exempt because it is less than 50% of the home's value. The fire marshal must decide what ignition-resistant construction and access improvements to require, and whether to require roof replacement.
1. What code and risk factors drive your review, and how would you treat the existing roof?
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The review is driven by the wildland-urban interface exposure, not by the percentage of project value. The 25% slope, the 15-ft distance to dense juniper and pine, the wood shake roof, the unenclosed deck, and the standard soffit vents are all ember and radiant-heat vulnerabilities. The existing roof is the most exposed component because embers can land on it and ignite the shake, and a roof fire can destroy the home even if the addition is built to a higher standard. Treat the roof as part of the project's life-safety package. Many WUI codes require Class A roof covering for new construction and additions, and some require replacement of an existing noncompliant roof when the addition exceeds a threshold or when the roof is already being replaced. Even if the local code does not mandate full replacement, the fire marshal can require it as a condition because the addition increases the home's exposure and the existing roof undermines the ignition-resistant features of the addition.
2. Identify the specific conditions you would attach to the addition permit and explain why each reduces risk.
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Require a Class A roof covering on the addition and, as a condition of approval, on the existing home if the roof is replaced or if the addition exceeds the local threshold. Require noncombustible or ignition-resistant siding on the addition, or a 1-hour exterior wall on the side facing the vegetation. Require the deck underside to be enclosed with ignition-resistant material, because embers accumulate under decks. Replace standard soffit vents with ember-resistant vents. Require a 5-ft noncombustible zone around the foundation and deck, and remove the juniper within the defensible-space zone. Require address signage visible from the road, and improve access by requiring turnouts or a turnaround on the 16-ft road if the local code allows a reduced width with mitigation. Require a water supply plan, such as a hydrant extension, a draft site, or a residential sprinkler system, given the 1,100-ft hydrant distance. Each condition targets a specific ignition pathway: roof, wall, underside, vent, and access.
3. How would you respond to the homeowner's exemption argument and the narrow road and hydrant issue?
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Explain that fire code review is not a value-based exemption. An addition can introduce new ignition-resistant requirements, and the existing roof and access conditions are part of the overall fire risk, even if the roof is not being replaced. If the local code allows an existing nonconforming roof to remain, do not simply waive the issue; document the risk and require the other mitigation measures, and require roof replacement at the next reroof. On access, a 16-ft road may be narrower than the standard 20 ft, but it can sometimes be approved with mitigation such as turnouts, vegetation clearance, and a turnaround. On water supply, the 1,100-ft hydrant distance is a serious deficiency; require a hydrant extension, a stored-water supply, or a residential sprinkler system, and verify that fire apparatus can reach the home. Give the homeowner a clear list of acceptable alternatives rather than a single costly demand. The goal is a defensible approval, not a denial.