Back To Board Minutes Listing Building Code Chapter 4 | Saturday, May 2, 2009







          Chapter 4 establishes the minimum criteria for light and ventilation and identifies occupancy limitations. 

          Section 401 outlines the scope of Chapter 4 (I.e., minimum light, ventilation and space requirements).  This section also establishes who is responsible for complying with the provisions of the chapter, permits alternative arrangements of windows and other devices to comply with the requirements for light and ventilation  and prohibits certain room arrangements  and occupancy uses. 

          Requirements for light, ventilation and space have not always been incorporated in construction and occupancy codes.  In the United States, one of the first attempts to establish criteria for light and ventilation occurred with the passage of the 1867 Tenement Housing Act in New York City.  A principal feature of the act required sleeping rooms to communicate directly with external air, or to have a ventilating window or transom connected to a neighboring room or hall. 

          In 1879, New York City passed a second Tenement Housing Act, which expanded the light and ventilation requirements of the 1867 law by mandating that windows have an opening of at least 12 square feet in every room.  Finally, New York City passed the Tenement Housing Act of 1901, which required owners to provide additional lighting and ventilation to all tenements.  Many other provisions also contributed to the health, safety and welfare of the  occupants. 

          Light, ventilation and space requirements relate to basic human needs.  In its Basic Principles of Healthful Housing, the Committee on the Hygiene of Housing of the American Public Health Association (APHA) established several principles regarding the relationship of housing to health.  These basic principles include several that relate specifically to the need for adequate light, ventilation and space, including physiological needs, psychological needs and protection against disease and accidents: 

Fundamental Physiological needs:

?             Provision of an atmosphere of reasonable chemical purity (proper      ventilation removes chemicals from the home and work      environment);

?             Provision of adequate daylight illumination and avoidance of undue          daylight glare;

?             Provision for admission of direct sunlight (the sun's rays assist in      killing germs);

?             Provision of adequate artificial illumination and avoidance of glare;      and

?             Provision of adequate space for exercise and for the play of children.


Fundamental Psychological needs:


?             Provision of adequate privacy for the individual; and

?              Provision of facilities that make possible the performance of      household tasks without undue physical and mental fatigue (adequate      space and sufficient ceiling heights reduce physical and mental      fatigue).


Protection against contagion:

?             Provision of sufficient space in sleeping rooms to minimize the      danger of contact infection.


Protection against accidents:

?             Provision of adequate facilities for escape in case of fire.


Protection against overcrowding:

?             Provision for population controls can maintain neighborhood density,      which can avoid overtaxing public facilities such as parks and      schools, and avoid accelerated wear of dwellings.


Habitable rooms require adequate light to assist occupants in providing for proper cleanliness and sanitation, and to reduce trip hazards.  Well-lighted rooms have a positive impact on mental health, while dark, dingy rooms can have the opposite effect. 

          Ventilation is defined as "the natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from any space."  Ventilating air into a space serves three functions: 

?             Combustion and makeup air for fuel-burning appliances is provided:

?             Air being exhausted from the building through mechanical or natural      means is replaced; and

?             Air movement within the structure is enhanced.


Ventilation air exhausting from a structure also serves there functions: 

?             Excess moisture is eliminated;

?             Unpleasant odors, toxic fumes, dirt, dust, and other particulate matter      are removed; and

?             Air movement within the structure is enhanced. 

          Oversized or improperly installed mechanical ventilation can cause fuel-burning appliances to back draft into the structure and may cause toxic materials to be exhausted into inappropriate locations. 

          Adequate space provides for the physical and mental health of occupants.  Crowded conditions have a negative impact on occupants by preventing easy movement throughout the dwelling.  Crowded conditions may also lead to accidents and injuries.  Additionally, occupants are subjected to an increase in the spread of disease and germs through sneezing and coughing. 

          Overcrowding may also have a negative effect on mental health.




          Minimum light, ventilation and  space requirements are based on the physiological and psychological impact of these factors on building occupants.  The purpose of Chapter 4 is to set forth these requirements in the code and to establish the minimum environment for occupiable and habitable buildings.







          401.1 SCOPE.  Buildings must comply with minimum criteria and conditions for light, ventilation and space.  Specific requirements are outlined in this chapter.


          401.2  RESPONSIBILITY.   The owner of the structure shall provide and maintain light, ventilation and space conditions in compliance with these requirements.  A person shall not occupy as owner-occupant, or permit another person to occupy, any premises that do not comply with the requirements of this chapter.


          The owner is responsible for complying with all light, ventilation and space requirements established in this chapter.  A non-complying structure cannot be occupied until it is brought into compliance with the criteria.


          401.3  ALTERNATIVE DEVICES.  In lieu of the means for natural light and ventilation herein prescribed, artificial light or mechanical ventilation complying with the International Building Code shall be permitted.


          Light and ventilation by artificial methods are permitted, such as electric lighting instead of natural light and mechanical ventilation instead of natural ventilation.  Electric lighting is permitted to replace the natural light requirements of Section 402.  Mechanical ventilation is permitted to replace the natural ventilation requirements of Section 403.  Any alternative method approved by the Code Official must also comply with the installation and performance requirements of the Building Code.















          402.1  HABITABLE SPACES.  Every habitable space shall have at least one window of approved size facing directly to the outdoors or to a court.  The minimum total glazed area for every habitable space shall be 8 percent of the floor area of such room.  Wherever walls or other portions of a structure face a window of any room and such obstructions are located less than 3 feet (914 mm) from the window and extend to a level above that of the ceiling of the room, such window shall not be deemed to face directly to the outdoors nor to a court and shall not be included as contributing to the required minimum total window area for the room.




          "Habitable space" is defined in Chapter 2.  Habitable spaces are those spaces that are normally considered "inhabited" in the course of residential living and provide the four basic characteristics of living, sleeping, eating, and cooking.  Other spaces, such as halls or utility rooms, are not considered habitable, but would in many instances be considered occupiable.


          As stated in Section 401.3, the natural lighting requirements of this section are not required if artificial light is provided.  Electric lighting is almost always provided.  Where electric lighting is provided instead of natural lighting, the Code Official must rely on a light meter to assess whether the illumination provided meets the criteria in the referenced Building Code.


          All habitable spaces must have at least one or more windows and the total glazed area must equal at least 8 percent of the floor area of the room they serve [see Figure 402.1(1)].


          Windows must face directly to the outdoors or to a court.  Any window that faces a wall or other obstruction that is less than 3 feet (914 mm) from the window and higher than the ceiling of the room cannot be included in calculating the minimum total window area needed for the room it serves [see Figure 402.1(2)].


          The exception addresses a case where a space (or room) has no glazed area open to the required courts or yards but is adjacent to one that does.  The internal room may "borrow" natural lighting from the adjacent space if the opening in the wall between the two spaces is at least 8 percent of the floor area of the interior room but not less than 25 square feet.  The required glazed area facing the required court or yard is to be based on the total floor area of all rooms served [see Figure 402.1(3)].


          In Figure 402.1(3), the glazed area opening onto a court or yard in the space provided with the openings must be greater than 8 percent of the total floor areas served; therefore, in Figure 402.1(3), the glazed area in Space B is required to be equal to or greater than 0.08 (floor area of Space A = floor area of Space B).


          The next step is to require the opening between the adjacent spaces to be a minimum of 25 square feet, but not less than 0.08 multiplied by the floor area of Space A.


          402.2 COMMON HALLS AND STAIRWAYS.  Every common hall and stairway in residential occupancies, other than in one- and two-family dwellings, shall be lighted at all times with at least a 60-watt standard incandescent light bulb for each 200 square feet of floor area or equivalent illumination, provided that the spacing between lights shall not be greater than 30 feet.  In other than residential occupancies, means of egress, including exterior means of egress, stairways shall be illuminated at all times the building space served by the means of egress is occupied with a minimum of 1 foot candle (11 lux) at floors, landings and treads.


          The intent of this section is to establish a minimum level of lighting in common halls and stairs of residential occupancies, such as apartment buildings. Adequate lighting in hallways and stairs is essential for safe exiting in a fire emergency, reduces the chance of injury due to falls during normal use and helps deter crime.

          This section contains a prescriptive requirement [60-watt light bulbs for every 200 square fee] for ease of application and enforcement (see Figure 402.2).  It assumes a typical ceiling height of no more than 10 feet (3048 mm).  Equivalent illumination by means other than 60-watt incandescent bulbs is explicitly permitted, and the Code Official would establish equivalency by judgment or by actually measuring with a light meter.  This lighting is required to be provided at all times, since residential buildings are typically occupied at all times.


          In all occupancy groups other than residential, a lower, minimum level of lighting [1 foot candle (11 lux)] threshold is consistent with the International Fire Code (IFC) and the International Building Code (IBC) for  acceptable lighting in means of egress components.


          402.3  OTHER SPACES.  All other spaces shall be provided with natural or artificial light sufficient to permit the maintenance of sanitary conditions, and the safe occupancy of the space and utilization of the appliances, equipment and fixtures.


          No specific criteria for minimum light and ventilation are established for other spaces, such as storage and utility rooms, closets and mud rooms.  All spaces, however, must have enough light to maintain their cleanliness and to allow for the safe use of appliances, equipment and fixtures located within them.



















          403.1  HABITABLE SPACES.  Every habitable space shall have at least one openable window.  The total openable area of the window in every room shall be equal to at least 45 percent of the minimum glazed area required in Section 402.1.




          As stated in Section 401.3, mechanical ventilation is an acceptable alternative to the natural ventilation requirements in this section.  Most detached single-family dwellings utilize natural ventilation.  Every habitable room (see the definition of "habitable space" in Chapter 2) must have one window that can be easily opened to provide natural ventilation.  In order to supply adequate natural ventilation, workable windows must be capable of opening to at least 45 percent of the minimum glazed area required for natural light, as established in Section 402.1 (see the definition of "openable area" in Chapter 2).  The openable area should be measured when the window or door is in its full, open position.  When determining openable area, only the space between stops or between stops and sashes is to be measured.  The areas of sashes, meeting rails, mullions, and muntins is to be deducted (see Figure 403.1).


          The exception allows for rooms to "share" required ventilation openings, as long as there are substantial interior openings between the rooms.  The example given in the commentary to Section 402.1 is applicable here (see commentary, Section 402.1).





          403.2  BATHROOMS AND TOILET ROOMS.  Every bathroom and toilet room shall comply with the ventilation requirements for habitable spaces as required by Section 403.1, except that a window shall not be required in such spaces equipped with a mechanical ventilation system.  Air exhausted by a mechanical ventilation system from a bathroom or toilet room shall discharge to the outdoors and shall not be recirculated.


          All bathrooms and toilet rooms must have windows that conform to the requirements of Section 402.1 for natural light and Section 403.1 for natural ventilation.  If a window is not provided or not large enough to comply with the light and ventilation requirements of these two sections, then an approved mechanical vent may be used.


          Mechanical ventilation in dwelling unit bathrooms and toilet rooms must exhaust all of the moisture-laden air to the exterior.  The vent must not terminate in any attic or other closed space (see Figure 403.2), which would allow moisture to condense on the building structure and lead to deterioration of the structure.


403.3  COOKING FACILITIES.  Unless approved through the certificate of occupancy, cooking shall not be permitted in any rooming unit or dormitory unit, and a cooking facility or appliance shall not be permitted to be present in the room unit or dormitory unit.






          Unless approval has been granted through a certificate of occupancy, cooking is prohibited in dormitory or rooming units (see the definition of "Rooming unit" in Chapter 2).  Cooking equipment is prohibited in these types of rooms, since cooking in sleeping areas may create fire and health hazards, as well as odor and moisture problems.





          Exception 1 provides for the allowance of cooking in a rooming unit or a dormitory unit based on written approval as granted by the Code Official.  Such an allowance should take into consideration the types of food to be cooked and the heat source and conditions under which the cooking will be done.  Requiring approval in writing verifies that there will be a traceable, verifiable record of the conditions of approval.  Such a record is useful in enforcing the conditions of the approval.  Exception 2 allows the use of coffee pots and microwave ovens in rooming units and dormitory units.  These types of appliances are typically used for short period of time and are currently used in hotel and motel units without significant problems.


          403.4  PROCESS VENTILATION.  Where injurious, toxic, irritating or noxious fumes, gases, dusts or mists are generated, a local exhaust ventilation system shall be provided to remove the contaminating agent at the source.  Air shall be exhausted to the exterior and not be re-circulated to any space.


          A mechanical vent, hood or cabinet is required when any process creates potentially hazardous fumes, gases or dust.  The ventilation has to be located at the source of the contamination and must exhaust directly to the exterior.  The criteria for new exhaust systems are found in the International Mechanical Code (IMC).  If the exhausted air contains dust, dirt, chemicals or other contaminants, the exhaust may require additional treatment to prevent contamination of the exterior air (see Figure 403.3).


          403.5  CLOTHES DRYER EXHAUST.  Clothes dryer exhaust systems shall be independent of all other systems and shall be exhausted in accordance with the manufacturer's instructions.


          Clothes dryers are prohibited from exhausting into other ventilation or exhaust systems.  Clothes dyers create large volumes of lint, dust and moisture that will clog or corrode any system not designed for this type of exhaust.  Additionally, the exhaust gases are hot and may contain combustion products.  Improper or inadequate provisions for exhaust may create a fire and health hazard.

          Manufacturers' installation instructions must be followed when exhausting clothes dryers.





          404.1 PRIVACY.  Dwelling units, hotel units, housekeeping units, rooming units and dormitory units shall be arranged to provide privacy and be separate from other adjoining spaces.


          Privacy is a fundamental psychological need.  Every person needs a space to relax, sleep and dress that is separate from public or common rooms.  Walls, corridors and doors should be arranged to offer the occupants their own private space.


          404.2  MINIMUM ROOM WIDTHS.  A habitable room, other than a kitchen, shall not be less than 7 feet (2134 mm) in any plan dimension.  Kitchens shall have a clear passageway of not less then 3 feet (914 mm) between countertrends and appliances or counter fronts and walls.


          To prevent the use of inadequately sized rooms for living space, the code establishes a minimum dimension of 7 feet (2134 mm) at the narrowest width of all habitable rooms, except kitchens.  Narrow rooms do not allow for the installation of furniture without unduly obstructing passageways through the rooms.  


                Kitchens require only 3 feet (914 mm) of clearance between countertops and appliances or countertops and walls.  Kitchens are not expected to be occupied for long periods of time, nor is it expected that kitchens will be occupied by a large number of persons at any one time.


          404.3  MINIMUM CEILING HEIGHTS.  Habitable spaces, hallways, corridors, laundry areas, bathrooms, toilet rooms and habitable basement areas shall have a clear ceiling height of not less than 7 feet (2134 mm).









           1.  In one and two-family dwellings, beams or girders spaced not less than 4 feet (1219 mm) on center and projecting not more than 6 inches (152 mm) below the required ceiling height.


     2.  Basement rooms in one and two-family dwellings occupied exclusively for laundry, study or recreation purposes, having a ceiling height of not less than 6 feet 8 inches (2033 mm) with not less than 6 feet 4 inches (1932 mm) of clear height under beams, girders, ducts and similar obstructions.


     3.  Rooms occupied exclusively for sleeping, study or similar purposes and having a sloped ceiling over all or part of the room, with a clear ceiling height of at least 7 feet (2134 mm) over not less than one-third of the required minimum floor area.  In calculating the floor area of such rooms, only those portions of the floor area with a clear ceiling height of 5 feet (1524 mm) or more shall be included.


          Sufficient ceiling heights are necessary to provide an adequate volume of air for occupants in closed spaces and to provide for their psychological well-being.  The height requirements are established by this section.


          To accommodate various conditions, the code establishes exceptions that permit a reduction in ceiling height within limited conditions.  These exceptions include the following:


          Exception 1 makes provisions for beams and girders to extend into the required minimum height.  This is consistent with the IBC and the International Residential Code (IRC) requirements, which allow this type of projection to accommodate structural members.


          Exception 2 is included to permit the use of existing basements with low headroom.  It is anticipated that these rooms will be used only occasionally and will not adversely affect the occupants' health or safety.


          Exception 3 is included to accommodate the many one and one-half story houses that have the sloped attic area finished into bedrooms and similar uses.

          Similar to the previous exception, the 7-foot high (2134 mm) ceiling must extend over one-third of the required area established in Section 404.4.1.  Thus, if a room is larger than the minimum required size for its use, the 7-foot-high (2134 mm)) portion may be less than one-third of the room's actual floor area.


EXAMPLE:  A bedroom of 175 square feet would be required to have a 7-foot-high (2134 mm) ceiling over no less than 23.3 square feet of the room area.  The minimum required area of a bedroom is 70 square feet (see Section 404.4.1); one-third of the required 70 square feet is 23.3 square feet.


          404.4  BEDROOM AND LIVING ROOM REQUIREMENTS.  Every bedroom shall comply with the requirements of Sections 404.4.1 through 404.4.5.


          The size of bedrooms and living rooms in a dwelling unit are a determining factor in the comfort and safety of occupants.  As such, the Code establishes minimum sizes and restricts certain configurations in regard to bathrooms, means of egress and other habitable rooms.


          404.4.1 ROOM AREA.  Every living room shall contain at least 120 square feet and every bedroom shall contain at least 70 square feet.


          The smallest bedroom allowed is 70 square feet.  This is barely enough space for a regular-sized bed and dresser.  The smallest living room allowed is 120 square feet.  Utilizing the minimum room width of 7 feet (2134 mm) would result in a living room size of approximately 7 feet by  17 feet (2134 mm by 5182 mm).  A more functional room size would perhaps be 10 feet by 12 feet (3048 mm by 3658 mm).


          404.4.2 ACCESS FROM BEDROOMS.  Bedrooms shall not constitute the only means of access to other bedrooms or habitable spaces and shall not serve as the only means of egress from other habitable spaces.






Every occupant must be provided with privacy in his or her sleeping room.  The need for privacy may lead occupants to lock or barricade doors in certain situations; therefore, if the only access to other habitable spaces or the means of egress is through a bedroom, there is a possibility that the only way out of a dwelling unit may be blocked in an emergency situation.  Even without an emergency, occupants may be seriously inconvenienced in their movement about the dwelling unit.  Bedrooms, therefore, must be arranged so that other occupants and guests do not have to pass through one bedroom to get to another bedroom or other habitable spaces (see Figure 404.4.2).  In addition, dwelling units must be configured such that occupants can egress from any habitable room in the dwelling unit without passing through a bedroom (see the commentary of Section 404.5 for examples of the application of this section).  The exception would permit a dwelling unit with only one bedroom to have an arrangement where the only access to habitable rooms or the means of egress is through the bedroom.  It is assumed in this case that only the occupants of this bedroom will require access to other rooms or the means of egress.


          404.4.3  WATER CLOSET ACCESSIBILITY.  Every bedroom shall have access to at least one water closet and one lavatory without passing through another bedroom.  Every bedroom in a dwelling unit shall have access to at least one water closet and lavatory located in the same story as the bedroom or an adjacent story.


Every occupant of a bedroom must have access to a water closet without having to pass through another room used as a bedroom.  Readily accessible water closets are important for privacy.  Occupants should be able to use bathroom facilities without compromising their modesty or the privacy of the occupants in a bedroom.  The requirement that every bedroom be served by a water closet and lavatory on the same floor level or on an adjacent level is considered an acceptable minimum  standard for the convenience of occupants.


          404.4.4  PROHIBITED OCCUPANCY.  Kitchens and non-habitable spaces shall not be used for sleeping purposes.


          The Code prohibits kitchens, interior public areas and non habitable spaces from being used as bedrooms.  These spaces provide neither privacy nor safety.  Such rooms may also lack adequate light, ventilation, fire exits and sufficient habitable space.


          This section provides the Code Official with another tool to control overcrowding problems.


          404.5  OVERCROWDING.  The number of persons occupying a dwelling unit shall not create conditions that, in the opinion of the Code Official, endanger the life, health, safety or welfare of the occupants.  


          Overcrowding is often a problem in rental properties and in small single-family dwellings.  Overcrowding can create serious problems; for example, disease spreads more easily, privacy is lost, mental health is affected and buildings are subject to more abuse and wear.  Overcrowding can have a destructive effect on a whole neighborhood if it takes place in several houses on the same block or in several units in the same apartment building.  Reducing overcrowding will reduce related health and safety hazards; therefore, this section gives the Code Official the authority to provide notice of a violation of overcrowding when in his or her opinion  an overcrowding condition exists.


          The code requires all types of dwelling units to comply with the minimum room area requirements. There is no exception for owner-occupied houses; however, overcrowding of owner-occupied, single-family residences requires the careful thought and judgment of the Code Official to determine an appropriate course of action.


          Proving that a building is overcrowded may be difficult.  Tenants may lie about the number of occupants in their unit to avoid eviction.  To determine the number of occupants, the Code Official may try to count beds or the names of mailboxes.  Neighbors may also provide information about the number of occupants and may be able to tell when the occupants are most likely to be home.  It may be necessary to conduct inspections during the evening hours in order to find an adult occupant at home.  School enrollment records can also provide information on the number of children occupying a residence.


          404.6  EFFICIENCY UNIT.  Nothing in this section shall prohibit an efficiency living unit from meeting the following requirements:


          1.  A unit occupied by not more than two occupants shall have a clear floor area of not less than 220 square feet.  A unit occupied by three occupants shall have a clear floor area of not less than 320 square feet.  These required areas shall be exclusive of the areas required by Items two (2) and three (3).


          2.  The unit shall be provided with a kitchen sink, cooking appliance, and refrigeration facilities, each having a clear working space of not less than 30 inches (762 mm) in front.  Light and ventilation conforming to the code shall be provided.


          3.  The unit shall be provided with a separate bathroom containing a water closet, lavatory and bathtub or shower.


          4.  The maximum number of occupants shall be three.


          Efficiency units are typically very small apartments consisting of one or two rooms and a bathroom.  Efficiency units that comply with this section are required to comply with the minimum area requirements for bedrooms in Section 404.4.  The total allowable number of occupants in the dwelling, however, is limited to two or three, depending on the area of the unit.  The purpose of efficiency units and this section is to provide for combined use of spaces in an economical or "efficient" manner without jeopardizing health or comfort.  This is possible because of the limit of total occupants to two or three persons.


          Item 1 establishes the minimum required area based on the number of occupants.  The item states that these areas are exclusive of the areas required by Items 2 and 3.  For example, Item 2 requires that the kitchen be provided with (as a minimum) a sink, cooking appliance and a refrigerator.  It further requires that each of these have a 30-inch (762 mm) clear working space in front of the fixture or appliance.  The space taken up by the appliance and the required clear working space of 30 inches (762 mm) in front of each appliance cannot be included in the minimum required floor space in Item 1.  Similarly, the floor area of the bathroom required in Item 3 is not included in the minimum required floor space in Item 1. Item 4 establishes the maximum occupant load as three.



          There are no minimum floor areas required in the kitchen or bathroom- there is enough space for the installation of the required fixtures or appliances in each room, and the specified working spaces for the kitchen.


          404.7  FOOD PREPARATION.  All spaces to be occupied for food preparation purposes shall contain suitable space and equipment to store, prepare and serve foods in a sanitary manner.  There shall be adequate facilities and services for the sanitary disposal of food wastes and refuse, including facilities for temporary storage.


          Kitchens must be provided with stoves, ovens, refrigerators, freezers, cabinets, countertops and drawers in sufficient quantity and in a condition that the occupants can store their food safely and at appropriate temperatures to protect the food.  All equipment must be constructed and maintained so that it can be cleaned.


          Food preparation areas must also be provided with garbage disposals or containers that permit the safe temporary storage of garbage and refuse.  Containers should be constructed and maintained to prevent insect and rate infestations.
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