Modified Fire Resistive Construction (ISO)
Definition
Modified Fire Resistive Construction (ISO) — one of six building construction categories established by Insurance Services
Office, Inc. (ISO), in its Commercial Lines Manual (CLM) for purposes
of developing rates for insuring commercial property, based on susceptibility
to damage by fire. The CLM description of modified fire resistive
construction, followed by the associated ISO construction code, is exterior
walls, floors, and roof of masonry or fire-resistive material with a fire
resistance rating of at least 1 hour, but less than 2 hours (Construction Code
5). The construction code indicates the ranking of this building construction
category within the six categories, with 1 as the least fire-resistive and 6 as
the most fire-resistive.