24 C.F.R. § 3280.215

(a) General. In manufactured homes with more than one dwelling unit, each dwelling unit must be separated from each other by wall and floor assemblies having not less than a 1 hour fire resistance rating when tested in accordance with ASTM E119 or UL 263 (both incorporated by reference, see § 3280.4) or having a fire resistance rating of not less than a 1 hour when calculated in accordance with chapter 16 of the AWC National Design Specification (NDS) for Wood Construction, with Supplement (incorporated by reference, see § 3280.4).

(b) Fire resistance walls. Fire-resistance-rated floor/ceiling and wall assemblies must extend to and be tight against the exterior wall, and wall assemblies must extend from the foundation to the underside of the roof sheathing except as follows:

(1) Wall assemblies need not extend through attic spaces where the ceiling is protected by not less than 5/8 inch Type X gypsum board and attic draftstop constructed as specified in § 3280.216 is provided above and along the wall assembly separating the dwelling units; and

(2) The structural framing supporting the ceiling is protected by not less than 1/2 inch gypsum board or equivalent.

(3) A fire resistance rating of 1/2 hour shall be permitted in buildings equipped throughout with an automatic sprinkler system installed in accordance with § 3280.214.

(c) Supporting construction. Where floor assemblies are required to be fire resistant rated by this section, the supporting construction of such assemblies must have an equal or greater fire resistance rating.

(d) Dwelling unit rated penetrations. Penetrations of wall or floor-ceiling assemblies in multi-dwelling unit manufactured homes are required to be fire-resistance rated in accordance with this section.

(1) Through penetrations. (i) Through penetrations must be installed as tested in the approved fire-resistance rated assembly; or

(ii) Through penetrations must be protected by an approved penetration fire stop system installed as tested in accordance with ASTM E814 or UL 1479 (both incorporated by reference, see § 3280.4), with a positive pressure differential of not less than 0.01 inch of water and must have an F rating of not less than the required fire resistance rating of the wall or floor-ceiling assembly penetrated; or

(iii) Where the penetrating items are steel, ferrous or copper pipes, tubes, or conduits, the material used to fill the annular space must prevent the passage of flame and hot gasses sufficient to ignite cotton waste where subjected to ASTM E119 or UL 263 (both incorporated by reference, see § 3280.4) time temperature fire conditions under a positive pressure differential of not less than 0.01 inch of water at the location of the through penetration for the time period equivalent to the fire resistance rating of the construction penetrated.

(2) Membrane penetrations. Membrane penetrations must comply with paragraph (d)(1) of this section. Where walls are required to have a fire resistance rating, recessed fixtures must be installed so that the required fire resistance rating will not be reduced except as follows:

(i) By membrane penetrations of fire-resistant-rated walls, ceiling/floors and partitions by steel electrical boxes provided they do not exceed 16 square inches in area and the aggregate area of the openings through the membrane does not exceed 100 square inches in any 100 square feet of wall area. The annular space between the wall membrane and the box must not exceed 1/8 inch. Such boxes on opposite sides of the wall must be separated by one of the following:

(A) A horizontal distance of not less than 24 inches where the wall or partition is constructed with individual non-communicating stud cavities; or

(B) A horizontal distance of not less than the depth of the wall cavity, where the wall cavity is filled with loose-fill insulation; or

(C) Solid fire blocking in accordance with § 3280.206; or

(D) Protecting both boxes with listed putty pads; or

(E) Other listed materials and methods.

(ii) By membrane penetrations of listed electrical boxes of any materials provided that the boxes have been tested for use in fire resistance rated assemblies and are installed in accordance with the instructions included with the listing. The annular space between the wall membrane and the box must not exceed 1/8 inch unless otherwise noted. Such boxes on opposite sides of the wall must be separated by one of the following:

(A) The horizontal distance specified in the listing of the electrical boxes; or

(B) Sold fire blocking in accordance with § 3280.206; or

(C) Protecting boxes with listed putty pads; or

(D) Other listed materials and methods.

(iii) By the annular space created by the penetration of a fire sprinkler provided that it is covered by a metal escutcheon plate.