ADUs and Fire Safety

What you should know and how to budget for Fire hazards.

There are two main categories to take into account when planning your ADU project, Fire truck access, and onsite mitigation to prevent fires.

1) Fire Truck Access

         A Fire truck needs to be able to park within a 150’ of all points of your residential structures.  If the structures have sprinklers, this distance can be 200’. This distance is not a straight line but is along the access path to pull a fire hose to all points of the on site structures.

         In addition, the fire truck must be able to turn around on a California Fire Code (CFC) compliant cul-de-sac or hammer head. This is not an issue for your normal gridded street layouts, but for dead ends, or large properties where the fire truck needs to turn around on the property. This would necessity improvements that the ADU builder will need construct which would be a costly, if not cost prohibitive,

2) Onsite Fire mitigation

          Fire Sprinkler are the most common form of onsite mitigation that the CFC often requires.  There is a myth that ADUs don’t need fire sprinklers if the primary dwelling does not have them. While this is mostly true, in cases where any portions of an ADU is more than 150’ from the fire truck parking location, sprinklers will be required.

          In cases where any portion of the ADU is farther than 200’ from the fire truck parking location, an approved fire truck turn around will need to be installed on site.  For narrow lots (less than 70’ wide) it is often impossible, which can prevent an ADU from being approved at all.

          Onsite Brush Management is also required in High Severity Fire zones. The required brush management areas are often larger than most infill lots.  While this will not stop your project from moving forward, it can add costs to construction, like fire treated wood, more expensive windows, etc.

           Lastly, if the ADUs are too far from a fire hydrant, fire departments can require you to install a new hydrant, which can be very expensive and negate the financial feasibility of your ADU project.

All of these issues are very nuanced and each project should be analyzed separately for fire safety and the subsequent ramifications.  Consult an expert in the planning phase of your project and start off on the right foot.