Subpart B states the planning requirements in manufactured homes. The intent of this subpart is to assure the adequacy of architectural planning considerations which assist in determining a safe and healthful environment.

(a) Gross floor area means all space, wall to wall, including recessed entries not to exceed 5 sq. ft. and areas under built-in vanities and similar furniture. Where the ceiling height is less than that specified in § 3280.104, the floor area under such ceilings shall not be included. Floor area of closets shall not be included in the gross floor area.

(b) Habitable room means a room or enclosed floor space arranged for living, eating, food preparation, or sleeping purposes not including bathrooms, foyers, hallways, and other accessory floor space.

(c) Laundry area means an area containing or designed to contain a laundry tray, clothes washer and/or clothes dryer.

(a) Lighting. Each habitable room shall be provided with exterior windows and/or doors having a total glazed area of not less than 8 percent of the gross floor area.

(1) Kitchens, bathrooms, toilet compartments, laundry areas, and utility rooms may be provided with artificial light in place of windows.

(2) Rooms and areas may be combined for the purpose of providing the required natural lighting provided that at least one half of the common wall area is open and unobstructed, and the open area is at least equal to 10 percent of the combined floor area or 25 square feet whichever is greater.

(b) Whole-house ventilation. Each manufactured home must be provided with whole-house ventilation having a minimum capacity of 0.035 ft 3/min/ft 2 of interior floor space or its hourly average equivalent. This ventilation capacity must be in addition to any openable window area. In no case shall the installed ventilation capacity of the system be less than 50 cfm. The following criteria must be adhered to:

(1) The ventilation capacity must be provided by a mechanical system or a combination passive and mechanical system. The ventilation system or provisions for ventilation must not create a positive pressure in Uo Value Zone 2 and Zone 3 or a negative pressure condition in Uo Value Zone 1. Mechanical systems must be balanced. Combination passive and mechanical systems must have adequately sized inlets or exhaust to release any unbalanced pressure. Temporary pressure imbalances due to gusting or high winds are permitted.

(2) The ventilation system or provisions for ventilation must exchange air directly with the exterior of the home, except the ventilation system, or provisions for ventilation must not draw or expel air with the space underneath the home. The ventilation system or provisions for ventilation must not draw or expel air into the floor, wall, or ceiling/roof systems, even if those systems are vented. The ventilation system must be designed to ensure that outside air is distributed to all bedrooms and main living areas. The combined use of undercut doors or transom grills connecting those areas to the room where the mechanical system is located is deemed to meet this requirement.

(3) The ventilation system or a portion of the system is permitted to be integral with the home's heating or cooling system. The system must be capable of operating independently of the heating or cooling modes. A ventilation system that is integral with the heating or cooling system is to be listed as part of the heating and cooling system or listed as suitable for use with that system.

(4) A mechanical ventilation system, or mechanical portion thereof, must be provided with a manual control, and must be permitted to be provided with automatic timers or humidistats.

(5) A whole-house ventilation label must be attached to the whole-house ventilation control, must be permanent, and must state: “WHOLE-HOUSE VENTILATION”.

(6) Instructions for correctly operating and maintaining whole-house ventilation systems must be included with the homeowner's manual. The instructions must encourage occupants to operate these systems whenever the home is occupied, and must refer to the labeled whole-house ventilation control.

(c) Additional ventilation. (1) At least half of the minimum required glazed area in paragraph (a) of this section shall be openable directly to the outside of the manufactured home for unobstructed ventilation. These same ventilation requirements apply to rooms combined in accordance with § 3280.103(a)(2).

(2) Kitchens shall be provided with a mechanical ventilation system that is capable of exhausting 100 cfm to the outside of the home. The exhaust fan shall be located as close as possible to the range or cook top, but in no case farther than 10 feet horizontally from the range or cook top.

(3) Each bathroom and separate toilet compartment shall be provided with a mechanical ventilation system capable of exhausting 50 cfm to the outside of the home. A separate toilet compartment may be provided with 1.5 square feet of openable glazed area in place of mechanical ventilation, except in Uo value Zone 3.

(d) Optional ventilation provisions. As an option to complying with the provisions of paragraphs (b) and (c) of this section, ventilation systems complying with ANSI/ASHRAE Standard 62.2 (incorporated by reference, see § 3280.4) may be used.

(a) Every habitable room and bathroom shall have a minimum ceiling height of not less than 7 feet, 0 inches for a minimum of 50 percent of the room's floor area. The remaining area may have a ceiling with a minimum height of 5 feet, 0 inches. Minimum height under dropped ducts, beams, etc. shall be 6 feet, 4 inches.

(b) Hallways and foyers shall have a minimum ceiling height of 6 feet, 6 inches.

(a) Number and location of exterior doors. Manufactured homes shall have a minimum of two exterior doors located remote from each other.

(1) Required egress doors shall not be located in rooms where a lockable interior door must be used in order to exit.

(2) In order for exit doors to be considered remote from each other, they must comply with all of the following:

(i) Both of the required doors must not be in the same room or in a group of rooms which are not defined by fixed walls.

(ii) Single wide units. Doors may not be less than 12 ft. c-c from each other as measured in any straight line direction regardless of the length of path of travel between doors.

(iii) Double wide units. Doors may not be less than 20 ft. c-c from each other as measured in any straight line direction regardless of the length of path of travel between doors.

(iv) One of the required exit doors must be accessible from the doorway of each bedroom without traveling more than 35 feet. The travel distance to the exit door must be measured on the floor or other walking surface along the center-line of the natural and unobstructed path of travel starting at the center of the bedroom door, curving around any corners or permanent obstructions with a one-foot clearance from, and ending at, the center of the exit door.

(b) Door design and construction. (1) Exterior swinging doors shall be constructed in accordance with § 3280.405 the “Standard for Swinging Exterior Passage Doors for Use in Manufactured Homes”. Exterior sliding glass doors shall be constructed in accordance with § 3280.403 the “Standard for Windows and Sliding Glass Doors Used in Manufactured Homes”.

(2) All exterior swinging doors must provide a minimum 28-inch wide × 74-inch high clear opening. Door seals are permitted to reduce the opening, either vertically or horizontally, a maximum of one inch. All exterior sliding glass doors must provide a minimum 28-inch wide × 72-inch high clear opening.

(3) Each swinging exterior door other than screen or storm doors shall have a key-operated lock that has a deadlocking latch or a key-operated dead bolt with a passage latch. Locks shall not require the use of a key for operation from the inside.

(4) All exterior doors, including storm and screen doors, opening outward shall be provided with a safety door check.

(a) Every room designed expressly for sleeping purposes, unless it has an exit door (see § 3280.105), shall have at least one outside window or approved exit device which meets the requirements of § 3280.404, the “Standard for Egress Windows and Devices for Use in Manufactured Homes.”

(b) The bottom of the window opening shall not be more than 36 inches above the floor.

(c) Locks, latches, operating handles, tabs, and any other window screen or storm window devices which need to be operated in order to permit exiting, shall not be located in excess of 54 inches from the finished floor.

(d) Integral rolled-in screens shall not be permitted in an egress window unless the window is of the hinged-type.

Bathroom and toilet compartment doors shall be equipped with a privacy lock.

(a) Interior doors having passage hardware without a privacy lock, or with a privacy lock not engaged, shall open from either side by a single movement of the hardware mechanism in any direction.

(b) Each manufactured home interior door, when provided with a privacy lock, shall have a privacy lock that has an emergency release on the outside to permit entry when the lock has been locked by a locking knob, lever, button, or other locking device on the inside.

(c) All interior swinging doors must have a minimum clear opening of 27 inches except doors to toilet compartments in single-section homes (see § 3280.111(b)), and doors to closets and pantries.

(a) Every manufactured home shall have at least one living area with not less than 150 sq. ft. of gross floor area.

(b) Rooms designed for sleeping purposes shall have a minimum gross square foot floor area as follows:

(1) All bedrooms shall have at least 50 sq. ft. of floor area.

(2) Bedrooms designed for two or more people shall have 70 sq. ft. of floor area plus 50 sq. ft. for each person in excess of two.

(c) Every room designed for sleeping purposes shall have accessible clothes hanging space with a minimum inside depth of 22 inches and shall be equipped with a rod and shelf.

The gross floor area required by § 3280.110 (a) and (b) shall have no clear horizontal dimension less than 5 feet except as permitted by § 3280.102(a).

(a) Each toilet compartment must be a minimum of 30 inches wide, except, when the toilet is located adjacent to the short dimension of the tub, the distance from the tub, to the center line of the toilet must not be less than 12 inches. At least 21 inches of clear space must be provided in front of each toilet.

(b) All bathroom passage doors in single-section homes must have a minimum clear opening width of 23 inches, and bathroom passage doors in multi-section homes must have a minimum clear opening width of 27 inches.

Hallways shall have a minimum horizontal dimension of 28 inches measured from the interior finished surface to the interior finished surface of the opposite wall. When appliances are installed in a laundry area, the measurement shall be from the front of the appliance to the opposite finished interior surface. When appliances are not installed and a laundry area is provided, the area shall have a minimum clear depth of 27 inches in addition to the 28 inches required for passage. In addition, a notice of the available clearance for washer/dryer units shall be posted in the laundry area. Minor protrusions into the minimum hallway width by doorknobs, trim, smoke alarms or light fixtures are permitted.

(a) Windows and sliding glass doors. All windows and sliding glass doors shall meet the requirements of § 3280.403 the “Standard for Windows and Sliding Glass Doors Used in Manufactured Homes”.

(b) Required glazed openings shall be permitted to face into a roofed porch where the porch abuts a street, yard, or court and the longer side of the porch is at least 65 percent open and unobstructed and the ceiling height is not less than 7 feet.

(c)Hazardous locations requiring safety glazing. Except as provided in paragraph (d) of this section, the following locations and areas require the use of safety glazing conforming to the requirements of paragraph (c) of this section:

(1) Glazing in all entrance or exit doors;

(2) Glazing in fixed and sliding panels of sliding glass doors;

(3) Glazing in storm-type doors;

(4) Glazing in unframed side-hinged swinging doors;

(5) Glazing in doors and fixed panels less than 60 inches above the room floor level that enclose bathtubs, showers, hydromassage tubs, hot tubs, whirlpools, saunas;

(6) Glazing within 12 inches horizontally, as measured from the edge of the door in the closed position, and 60 inches vertically as measured from the room floor level, adjacent to and in the same plane of a door;

(7) Glazing within 36 inches of an interior room walking surface when the glazing meets all of the following:

(i) Individual glazed panels exceed 9 square feet in area in an exposed surface area;

(ii) The bottom edge of the exposed glazing is less than 19 inches above the room floor level; and

(iii) The top edge of the exposed glazing is greater than 36 inches above the room floor level.

(8) Glazing in rails and guardrails; and

(9) Glazing in unbacked mirrored wardrobe doors (i.e., mirrors that are not secured to a backing that is capable of being the door itself).

(d) Safety glazing material is considered to be any glazing material capable of meeting the requirements of Consumer Product Safety Commission 16 CFR part 1201, or Standard for Safety Glazing Materials used in Buildings —Safety Performance Specifications and Methods of Test, ANSI Z97.1-2004 (incorporated by reference, see § 3280.4).

(e) Glazing in the following locations is not required to meet the requirements in paragraph (b) of this section:

(1) Openings in doors through which a 3-inch sphere is unable to pass;

(2) Leaded and decorative glazed panels;

(3) Glazing in jalousie-type doors;

(4) Glazing as described in paragraph (b)(6) of this section when an intervening wall or other permanent barrier exists between the door and the glazing;

(5) Glazing as described in paragraph (b)(7) of this section when a protective bar or member is installed horizontally between 34 inches and 38 inches above the room floor level, as long as the bar or member is a minimum of 1 1/2 inches in height and capable of resisting a horizontal load of 50 pounds per lineal foot; and

(6) Mirrors mounted on a flush door surface or solid wall surface.

(a) Stairways—(1) General. These minimum standards apply to stairways that are designed and constructed as part of the factory-completed transportable section(s) of a manufactured home, such as interior stairways for multi-level or multi-story homes or external stairways for multi-level construction features that are designed and constructed in the factory on a transportable section and integral to the access and egress needs within the transportable section(s) of a home. These standards do not apply to exterior stairways that are built at the home site or stairways to basement areas that are not designed and built as part of a transportable section of a manufactured home.

(2) Width. Stairways must not be less than 36 inches in clear width at all points above permitted handrail height and below the required headroom height. Handrails must not project more than 4 1/2 inches on either side of the stairway and the minimum clear width of the stairway at and below the handrail height, including treads and landings, must not be less than 31 1/2 inches where a handrail is installed on one side and 27 inches where handrails are provided on both sides.

(3) Stair treads and risers—(i) Riser height and tread depth. The maximum riser height must not exceed 8 1/4 inches and the minimum tread depth must not be less than 9 inches. The riser height must be measured vertically between leading edges of the adjacent treads. The tread depth must be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's leading edge. The walking surface of treads and landings of a stairway must be sloped no steeper than one unit vertical in 48 units horizontal (a 2-percent slope). The greatest riser height within any flight of stairs must not exceed the smallest by more than 3/8 inch. The greatest tread depth within any flight of stairs must not exceed the smallest by more than 3/8 inch.

(ii) Profile. The radius of curvature at the leading edge of the tread must not be greater than 9/16 inch. A nosing not less than 3/4 inch but not more than 1 1/4 inches shall be provided on stairways with solid risers. The greatest nosing projection must not exceed the smallest nosing projection by more than 3/4 inch between two stories, including the nosing at the level of floors and landings. Beveling of nosing must not exceed 1/2 inch. Risers must be vertical or sloped from the underside of the leading edge of the tread above at an angle not more than 30 degrees from the vertical. Open risers are permitted, provided that the opening between treads does not permit the passage of a 4-inch diameter sphere. A nosing is not required where the tread depth is a minimum of 11 inches. The opening between adjacent treads is not limited on stairs with a total rise of 30 inches or less.

(4) Headroom. The minimum headroom in all parts of the stairway must not be less than 6 feet 8 inches, measured vertically from the sloped plane adjoining the tread nosing or from the floor surface of the landing or platform.

(5) Winders (winding stairways). Winders are permitted, provided that the width of the tread at a point not more than 12 inches from the side where the treads are narrower is not less than 10 inches and the minimum width of any tread is not less than 6 inches. Within any flight of stairs, the greatest winder tread depth at the 12-inch walk line must not exceed the smallest by more than 3/8 inch. The continuous handrail required by paragraph (c)(3) of this section must be located on the side where the tread is narrower.

(6) Spiral stairways. Spiral stairways are permitted provided the minimum width is a minimum 26 inches with each tread having 7 1/2 inch minimum tread width at 12 inches from the narrow edge. All treads must be identical, and the rise must be no more than 9 1/2 inches. Minimum headroom of 6 feet, 6 inches must be provided.

(7) Circular stairways. Circular stairways must have a tread depth at a point not more than 12 inches from the side where the treads are narrower of not less than 11 inches and the minimum depth of any tread must not be less than 6 inches. Tread depth at any walking line, measured a consistent distance from a side of the stairway, must be uniform as specified in paragraph (a)(2)(i) of this section.

(b) Landings. Every landing must have a minimum dimension of 36 inches measured in the direction of travel. Landings must be located as follows:

(1) There must be a floor or landing at the top and bottom of each stairway, except at the top of an interior flight of basement stairs, provided a door does not swing over the stairs.

(2) A landing or floor must be located on each side of an interior doorway and exterior doorway, to the extent the external stairway is designed by the home manufacturer and constructed in the factory, and the width of each landing must not be less than the door it serves. The maximum threshold height above the floor or landing must be 1 1/2-inches.

(c) Handrails—(1) General. A minimum of one handrail meeting the requirements of this section must be installed on all stairways consisting of four or more risers. Handrails must be securely attached to structural framing members. A minimum space of 1 1/2 inches must be provided between the adjoining wall surface and the handrail.

(2) Handrail height. Handrails must be installed between 34 inches and 38 inches measured vertically from the leading edge of the stairway treads except that handrails installed up to 42 inches high must be permitted if serving as the upper rails of guards required by paragraph (d) of this section.

(3) Continuity. Required handrails must be continuous from a point directly above the leading edge of the lowest stair tread to a point directly above the leading edge of the landing or floor surface at the top of the stairway. If the handrail is extended at the top of the stairway flight, the extension must parallel the floor or landing surface and must be at the same height as the handrail above the leading edges of the treads. If the handrail is extended at the base of the stair, it must continue to slope parallel to the stair flight for a distance of one tread depth, measured horizontally, before being terminated or returned or extended horizontally. The ends of handrails must return into a wall or terminate in a safety terminal or newel post.

(4) Graspability. Required handrails must, if circular in cross section, have a minimum 1 1/4-inch and a maximum 2-inch diameter dimension. Handrails with a noncircular cross section must have a perimeter dimension of at least 4 inches and not more than 6 1/4 inches (with a maximum cross-section dimension of not more than 2 1/4 inches). The handgrip portion of the handrail must have a smooth surface. Edges must have a minimum 1/8-inch radius. Handrails must be continuously graspable along their entire length except that brackets or balusters are not considered obstructions to graspability if they do not project horizontally beyond the sides of the handrail within 1 1/2 inches of the bottom of the handrail.

(5) Required resistance of handrails. Handrails must be designed to resist a load of 20 lb./ft applied in any direction at the top and to transfer this load through the supports to the structure. All handrails must be able to resist a single concentrated load of 200 lbs., applied in any direction at any point along the top, and have attachment devices and supporting structures to transfer this loading to appropriate structural elements of the building. This load is not required to be assumed to act concurrently with the loads specified in this section.

(d) Guards. (1) Porches, balconies, or raised floor surfaces located more than 30 inches above the floor or grade below must have guards not less than 36 inches in height. Open sides of stairs with a total rise of more than 30 inches above the floor or grade below must have guards not less than 34 inches in height measured vertically from the nosing of the treads. Balconies and porches on the second floor or higher must have guards a minimum of 42 inches in height.

(2) Required guards on open sides of stairways, raised floor areas, balconies, and porches must have intermediate rails or ornamental closures that do not allow passage of a sphere 4 inches in diameter.

(i) The triangular openings formed by the riser, tread and bottom rail of a guard at the open side of the stairway must be of such a size that a sphere of 6 inches cannot pass through.

(ii) Guard systems must be designed to resist a load of 20 lb./ft applied in any direction at the top and to transfer this load through the supports to the structure. All guard systems must be able to resist a single concentrated load of 200 lb., applied in any direction at any point along the top and have attachment devices and supporting structures to transfer this loading to appropriate structural elements of the building. This load is not required to be assumed to act concurrently with the loads specified in this section.

(e) Stairway illumination. All interior and exterior stairways must be provided with a means to illuminate the stairways, including the landings and treads.

(1) Interior stairways must be provided with an artificial light source located in the immediate vicinity of each landing of the stairway. For interior stairs, the artificial light sources must be capable of illuminating treads and landings to levels not less than one (1) foot-candle measured at the center of treads and landings. The control and activation of the required interior stairway lighting must be accessible at the top and bottom of each stairway without traversing any steps.

(2) Exterior stairways designed by the home manufacturer and constructed in the factory must be provided with an artificial light source located in the immediate vicinity of the top landing of the stairway. An artificial light source is not required at the top and bottom landing, provided an artificial light source is located directly over each stairway section. The illumination of exterior stairways must be controlled from inside the home.