What is the fire separation between units in a duplex?
The two units of a two-family dwelling must be separated by walls and floor/ceiling assemblies with at least a 1-hour fire-resistance rating (IRC R302.3).
In a two-family dwelling (duplex), the units must be separated from each other by both wall and floor/ceiling assemblies rated for not less than 1 hour of fire resistance.
Where the building is protected throughout by an approved automatic sprinkler system, the IRC allows the separation to be reduced to a 1/2-hour (30-minute) rating.
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