2021 IRC R314, R315, R308
Where Lesson 13 covered getting out of the house, this lesson covers what wakes someone up in time to get out, and what keeps ordinary glass from becoming a weapon when a person falls into it. Sections R314 and R315 set smoke and carbon monoxide alarm requirements, R308 sets where glazing must be the tempered or laminated safety type, and R302.9-R302.10 set limits on how fast interior finishes and insulation can carry a flame. None of these are structural in the way a footing or a header is, but they are consistently the numbers that determine whether occupants survive a fire or a fall that has already started.
R314.3 requires a smoke alarm in each sleeping room, outside each separate sleeping area in the immediate vicinity of the bedrooms, and on each additional story of the dwelling, including basements and habitable attics (crawl spaces and uninhabitable attics are excluded). A two-story house with a basement and three upstairs bedrooms needs at minimum six alarms under this rule: one in each of the three bedrooms, one in the upstairs hall outside the sleeping area, one on the main floor, and one in the basement. In a split-level dwelling with no door between the adjacent levels, an alarm on the upper level can serve a lower level that is less than one full story below it, but the basic pattern is the same everywhere: an alarm close enough to sleepers to wake them, on every level people occupy.
In new construction, smoke alarms must receive their primary power from the building wiring, with battery backup, and must be interconnected so that activating any one alarm sounds every alarm in the dwelling (R314.6, R314.4), and listed wireless alarms can meet the interconnection requirement. A fire starting in a basement has to be able to wake someone sleeping two floors up, which interconnection accomplishes and a standalone battery alarm on each floor does not. Placement is also restricted near features that cause nuisance alarms: an alarm may not be installed within 3 feet horizontally of the door or opening of a bathroom containing a tub or shower, because shower steam trips alarms and alarms that trip constantly get disabled by occupants. Section R314.3.1 keeps alarms away from permanently installed cooking appliances by a distance that depends on the alarm type: not less than 20 feet for ionization alarms, 10 feet for ionization alarms with a silencing switch, and 6 feet for photoelectric alarms or alarms marked as helping reduce cooking nuisance alarms, unless that would prevent placing an alarm that R314.3 requires.
For alterations, repairs, and additions that require a permit, Section R314.2.2 requires the dwelling unit to have smoke alarms located as required for new dwellings, and R314.6 (Exception 2) permits those alarms to be battery powered. Work limited to exterior surfaces (roofing, siding, windows, doors, a porch or deck) or to plumbing or mechanical systems is excepted. This keeps a modest repair from forcing a homeowner to tear open finished walls just to run alarm wiring.
R315.2.1 requires carbon monoxide alarms in new dwelling units that contain a fuel-fired appliance or have an attached garage with an opening into the dwelling, and R315.3 places them outside each separate sleeping area in the immediate vicinity of the bedrooms, on the same reasoning as smoke alarms: occupants are most vulnerable to CO while asleep. Where a fuel-burning appliance is located within a bedroom or its attached bathroom, such as a gas-fired wall furnace, an additional CO alarm is required inside the bedroom, because an alarm outside the door is too far away to protect the person sleeping next to the source. Section R315.2.2 extends the requirement to permitted alterations, repairs, and additions, except exterior-surface work, plumbing, and mechanical work that is not fuel fired.
R308.4 lists these hazardous locations, and the pattern behind them is consistent: any place where a person's own momentum, wet feet, or a slip near a door could put a body through ordinary glass gets the tempered or laminated safety-glazing requirement instead. The large-panel test is the one most often applied incorrectly in the field because it has four separate conditions that all must be met at once; a panel that is large enough but has its bottom edge well above 18 inches, for example, does not trigger the requirement, because that condition alone is missing.
Each pane of safety glazing must carry a manufacturer's designation stating who applied it, the type of glass, and the safety standard it meets, and the designation must be visible in the final installation (R308.1). It is acid etched, sandblasted, ceramic-fired, laser etched, embossed, or of a type that cannot be removed without being destroyed, and a label is permitted in lieu of it. The point is a mark an inspector can verify without breaking the pane.
R302.9 limits interior wall and ceiling finish materials to a flame spread index of not greater than 200 and a smoke-developed index of not greater than 450, tested to ASTM E84 or UL 723; trim such as baseboards and handrails, and doors and windows or their frames, are excepted from the flame spread limit. R302.10.1 sets a tighter limit for insulation in floor-ceiling, roof-ceiling, and wall assemblies, crawl spaces, and attics, including facings: a flame spread index of not greater than 25 and a smoke-developed index of not greater than 450, because insulation and its facings are normally concealed behind a finish surface and can spread fire very quickly if left exposed. A facing in a concealed space, installed in substantial contact with the unexposed surface of the finish, such as a kraft-faced batt stapled tight behind drywall, is excused from the limits by Exception 1; the same facing left exposed to a room or garage is not. Kraft-faced batts installed with the facing left exposed in a garage ceiling, a common finding in older additions, are a straightforward violation: the facing is not in a concealed space and does not meet the limit, so it must be covered by a finish with the facing in substantial contact with it. Exposed insulation on an attic floor must also have a critical radiant flux of at least 0.12 watt per square centimeter (R302.10.4).
In the field
A GCHS inspector reviewing a bedroom addition or a basement conversion has to confirm alarms and glazing at the same visit as everything from Lesson 13, because a sleeping room sits at the intersection of several chapters at once. A room can have perfect ceiling height, floor area, and an oversized egress window and still fail for sleeping use if it has no smoke alarm, or if a fixed glass panel next to the entry door sits at 30 inches above the floor with no safety marking. Any one of these failures, not just a combination of several, is enough to keep the room from being approved.
An addition has an entry door with a fixed glass sidelite mounted 10 inches from the door edge, bottom edge 8 inches above the floor, top edge 74 inches above the floor, panel area 14 square feet. Two separate hazardous-location tests can apply to the same panel, and either one alone is enough to require safety glazing. First, the door-proximity test: the sidelite is within 24 inches of the door and its bottom edge, at 8 inches, is well under 60 inches, so it is hazardous under that rule by itself. Second, the large-panel test: area is 14 square feet (over 9), bottom edge is 8 inches (under 18), top edge is 74 inches (over 36), and the panel sits at a walking surface within 36 inches of the door threshold, so all four large-panel conditions are also met. Either test would have required safety glazing here on its own; that the panel fails both is not unusual, since doors and their sidelites are exactly where these hazardous-location categories overlap most.
1. A new two-story house has a basement and three bedrooms upstairs. Which locations must ALL have a smoke alarm?
2. In new construction, what must be true about smoke alarm power and interconnection?
3. In a permitted alteration of an existing dwelling, how must smoke alarms be provided?
4. A smoke alarm may generally not be installed within 3 feet horizontally of what location, and why?
5. Carbon monoxide alarms are required in a dwelling that has:
6. A bedroom contains a gas-fired wall furnace. What additional carbon monoxide alarm requirement applies?
7. A fixed glass panel sits 12 inches from the edge of an entry door, bottom edge 30 inches above the floor. Is safety glazing required?
8. A 12-square-foot fixed glass panel has its bottom edge 12 inches above the floor and its top edge 8 feet above the floor, next to a hallway. Is safety glazing required under the large-panel test?
9. Glazing enclosing a bathtub or shower is a hazardous location when its bottom exposed edge is less than what height above the standing or walking surface?
10. Each pane of safety glazing in a hazardous location must carry a manufacturer's designation that is:
11. Interior wall and ceiling finish materials are limited under R302.9 to a flame spread index of not greater than:
12. Insulating materials installed in wall, ceiling, attic, and crawl-space assemblies, including their facings, are limited under R302.10.1 to a flame spread index of not greater than:
13. An inspector finds kraft-faced batt insulation in a garage ceiling with the facing left exposed to the garage space. What is the finding?
14. An entry door has a fixed sidelite 10 inches from the door edge, bottom edge 8 inches above the floor, top edge 74 inches above the floor, area 14 square feet. Which hazardous-location tests apply?