New Form INC

11.6 mezzanines as intermediate floors (model type 4)

Mezzanine floors are a special case, most often associated with offices forming part of an industrial or commercial building. The Acceptable solution uses the notion of a “limited area intermediate floors” to account for mezzanines.

While there are unique requirements with regard to intermediate floors, they generally have a fire rating requirement of 30/30/30 which is equal to the nominal 30 minute FRR rating provided by a tray floor without emergency fire reinforcement.

In general a limited are intermediate floor is restricted to posses a floor area as follows
(a) 20% of the area of the Firecell floor area where intermediate floors are enclosed or partitioned.

(b) 40% of the area of the firecell floor area where the intermediate floors are completely open.
It is to be noted that there are other particular requirements with regard to intermediate floors and advice from a fire design consultant should be obtained at a project’s conceptual stage to ensure pertinent aspects are considered. Intermediate floors can not be enclosed with fire rated walls, otherwise new firecells are created.

Examples of buildings containing limited area intermediate floors which could meet the requirements of the acceptable solutions include, factories, warehouses, churches, halls, small theatres, gymnasiums, shops and offices, but specifically excludes car parking buildings.

“Limited area atrium” firecells incorporating intermediate floors are not considered in this manual.