Product Documentation

Defensible Space - Frequently Asked Questions (FAQ)

What AI generations support Defensible Space?

Defensible Space is only available on Gen6 AI. So, the request must include systemVersionPrefix=gen6.

Which feature classes can include Defensible Space data?

If allowed by the calling account's packs, the response will contain both 'Roof' and 'Building Lifecycle' feature classes. Both of these feature classes can support the Defensible Space feature, but only one will be used per building. The default is for the Defensible Space data to be attached to the Roof feature class. However, if the building's roof is severely damaged or destroyed, the Defensible Space data will instead be attached to the Building Lifecycle class.

Is there always a one-to-one relationship between Roof and Building Lifecycle?

No. Sometimes a building may have many roofs, and sometimes a single damaged roof will have become multiple separate roof areas. Therefore, there is not always a one-to-one relationship. However, a one-to-one relationship is the most common.

Why are zones exclusive rings rather than inclusive areas?

The zone design as exclusive rings (Zone 2 = 5-30 ft only, not 0-30 ft) allows for more granular analysis of risk at different distances from the structure. This aligns with how defensible space guidelines typically assess risk at different distances. It also aligns with CAL Fire’s defensible space boundaries

What happens if there are no risk objects in a zone?

If a zone contains no risk objects, the riskObjects array will be empty [], and the totalRiskObjectAreaSqm will be 0. The defensible space coverage ratio will be 1.0 (100%).

Are geometries returned in the response?

Yes. Both zone geometries and clipped risk object geometries are included in the response. These geometries are provided in WGS84 (EPSG:4326) coordinate reference system.

What units are used in the response?

The response includes both metric (square meters, meters) and imperial (square feet, feet) measurements for all area and distance values.

Can custom zone definitions be requested?

The current implementation uses the standard 3-zone model (0-5 ft, 5-30 ft, 30-100 ft). Custom zone definitions are not currently supported via the API but may be considered for future releases.

How is the aggregate (property-level) defensible space calculated?

The aggregate result is calculated from the union of all geometries of features within the parcel that have defensible space associated with them. Zones are generated around this merged geometry, and risk objects within these zones are analyzed to produce property-wide coverage metrics.

If a building footprint is clipped to the parcel boundary, will any risk objects belonging to the structure, for example a deck, be clipped also?

No, not at this time.

Often a feature does not have clippedGeometry, but does have clippedAreaSqm. Why?

This happens when a sliver of a feature is beyond the parcel boundary, but does not belong to the adjoining parcel (see note in the Parcel Mode documentation). The clippedAreaSqm tells you how much of the feature is in the boundary whilst this clipped data is not used for processing attributes and scores such as Defensible Space.

Which peril scores use Defensible Space data?

Defensible Space coverage metrics are used as inputs to:

Hurricane Vulnerability Score (defensible space coverage per zone)
Wildfire Vulnerability Score (defensible space coverage and yard debris coverage per zone)
Wind Vulnerability Score (building coverage per zone)

The peril scores use only the coverage metrics, not the geometries.

Can Defensible Space be retrieved for any AOI?

It is strongly recommended that the AOI aligns with a property/parcel boundary and that the parcelMode=true parameter is used. This will provide Defensible Space for a property/parcel. However, it is possible to provide any AOI.