So where would you think smoke alarms would work best in your home? You could start guessing and as long as you guess every room except bathrooms with showers you would only have to move one smoke alarm in the kitchen. Sounds easy enough, but, maybe your builder doesn't want to load up your home with smoke alarms or simply doesn't want to have to install them. 

Here's what I have researched that should make your life designing your smoke alarm system easier. 

Resources: 

• NFPA 72
• IRC
• ICC discussions
• Installation and user manual of your favorite smoke alarm

First part in adding smoke alarms to your design is very easy reading Section No. 29.11.3.4 Specific Location Requirements.

I'll be using our home design which is a very good example because of the required 12 smoke alarms interconnected. 

Example Residential home: 

• 6 bedrooms
• 4 bathrooms (location of door to showers are important here.)
• 2 12 foot hallways with 3 feet of the ceiling air return register and bathroom door within 36" of bedroom doors.
• Habitable storage attic within thermal envelope with unvented roof and fixed staircase open to attic.

With the 6 bedrooms and hallway we know that we will need one smoke alarm for each bedroom and one smoke alarm in each hallway centered to the bedroom doors. 

• That makes 8 smoke alarms so far that have to be interconnected. 

Next we have a narrow open kitchen connected to family room and another room the same size with kitchenette and entertainment room. Both rooms measure 15' x 35' which when using the Point 7 Rule (70% of a 21' radius circle covered) we cover that area with a single smoke detector near center of the room. 

• That makes a total of 10 smoke alarms to this point. 

Next we have fixed stairs leading to an attic used for storage and built to code following Habitable Attic (by IRC definition) building codes. The attic is 37' x 36' but not used for living so it requires only one smoke detector by code above the open stair opening and below the peak (ridge beam) by 3 feet. The design is a split attic with 2 staircases which means we need 2 smoke detectors one for each top of staircase location.  

• That makes a total of 12 smoke alarms to this point and final for most residential homes that are required to interconnect their alarms. 

We also have an entrance gallery (foyer) which has two open 40" doors with a ceiling rafter assembly that is not part of the conditioned space. It also acts as a transitional room such as a mudroom. This room will have a heat and smoke alarm not interconnected to the other alarms due to manufacturers restrictions of 12 smoke alarms per circuit interconnect. 

Here is the list of codes that I used to identify the required interconnected alarms for a large home. Keep in mind that this is our design and we had to establish room types per IRC and ICC before we consulted the NEC and NFPA.

IRC-2015 [RB] ATTIC, HABITABLE. A finished or unfinished area, not considered a story, complying with all of the following requirements:

1. The occupiable floor area is not less than 70 square feet (17 m2), in accordance with Section R304.
2. The occupiable floor area has a ceiling height in accordance with Section R305.
3. The occupiable space is enclosed by the roof assembly above, knee walls (if applicable) on the sides and the floor-ceiling assembly below.

IRC-2015 Section R314

R314.3 Location. Smoke alarms shall be installed in the following locations:

1. In each sleeping room.
2. Outside each separate sleeping area in the immediate vicinity of the bedrooms.
3. On each additional story of the dwelling, including basements and habitable attics and not including crawl spaces and uninhabitable attics. In dwellings or dwelling units with split levels and without an intervening door between the adjacent levels, a smoke alarm installed on the upper level shall suffice for the adjacent lower level provided that the lower level is less than one full story below the upper level.
4. Smoke alarms shall be installed not less than 3 feet (914 mm) horizontally from the door or opening of a bathroom that contains a bathtub or shower unless this would prevent placement of a smoke alarm required by Section R314.3.

R314.3.1 Installation near cooking appliances. Smoke alarms shall not be installed in the following locations unless this would prevent placement of a smoke alarm in a location required by Section R314.3.

1. Ionization smoke alarms shall not be installed less than 20 feet (6096 mm) horizontally from a permanently installed cooking appliance.
2. Ionization smoke alarms with an alarm-silencing switch shall not be installed less than 10 feet (3048 mm) horizontally from a permanently installed cooking appliance.
3. Photoelectric smoke alarms shall not be installed less than 6 feet (1828 mm) horizontally from a permanently installed cooking appliance.

R314.4 Interconnection. Where more than one smoke alarm is required to be installed within an individual dwelling unit in accordance with Section R314.3, the alarm devices shall be interconnected in such a manner that the actuation of one alarm will activate all of the alarms in the individual dwelling unit. Physical interconnection of smoke alarms shall not be required where listed wireless alarms are installed and all alarms sound upon activation of one alarm.

Exception: Interconnection of smoke alarms in existing areas shall not be required where alterations or repairs do not result in removal of interior wall or ceiling finishes exposing the structure, unless there is an attic, crawl space or basement available that could provide access for inter connection without the removal of interior finishes.

IRC-2015 Sections R304 and R305

SECTION R304 MINIMUM ROOM AREAS
R304.1 Minimum area. Habitable rooms shall have a floor area of not less than 70 square feet (6.5 m2).
Exception: Kitchens.
R304.2 Minimum dimensions. Habitable rooms shall be not less than 7 feet (2134 mm) in any horizontal dimension.
Exception: Kitchens.
R304.3 Height effect on room area. Portions of a room with a sloping ceiling measuring less than 5 feet (1524 mm) or a furred ceiling measuring less than 7 feet (2134 mm) from the finished floor to the finished ceiling shall not be considered as contributing to the minimum required habitable area for that room.

SECTION R305 CEILING HEIGHT
R305.1 Minimum height. Habitable space, hallways and portions of basements containing these spaces shall have a ceiling height of not less than 7 feet (2134 mm). Bathrooms, toilet rooms and laundry rooms shall have a ceiling height of not less than 6 feet 8 inches (2032 mm).
Exceptions:

1. For rooms with sloped ceilings, the required floor area of the room shall have a ceiling height of not less than 5 feet (1524 mm) and not less than 50 percent of the required floor area shall have a ceiling height of not less than 7 feet (2134 mm).
2. The ceiling height above bathroom and toilet room fixtures shall be such that the fixture is capable of being used for its intended purpose. A shower or tub equipped with a shower head shall have a ceiling height of not less than 6 feet 8 inches (2032 mm) above an area of not less than 30 inches (762 mm) by 30 inches (762 mm) at the shower head.
3. Beams, girders, ducts or other obstructions in basements containing habitable space shall be permitted to project to within 6 feet 4 inches (1931 mm) of the finished floor.

R305.1.1 Basements. Portions of basements that do not contain habitable space or hallways shall have a ceiling height of not less than 6 feet 8 inches (2032 mm).
Exception: At beams, girders, ducts or other obstructions, the ceiling height shall be not less than 6 feet 4 inches (1931 mm) from the finished floor.

IRC-2015 APPENDIX M SECTION AM104 SMOKE DETECTION

AM104.3 Location.

A detector shall be located in each bedroom and any room that is to be used as a sleeping room, and centrally located in the corridor, hallway or area giving access to each separate sleeping area. When the dwelling unit has more than one story, and in dwellings with basements, a detector shall be installed on each story and in the basement. In dwelling units where a story or basement is split into two or more levels, the smoke detector shall be installed on the upper level, except that when the lower level contains a sleeping area, a detector shall be installed on each level. When sleeping rooms are on the upper level, the detector shall be placed at the ceiling of the upper level in close proximity to the stairway. In dwelling units where the ceiling height of a room open to the hallway serving the bedrooms or sleeping areas exceeds that of the hallway by 24 inches (610 mm) or more, smoke detectors shall be installed in the hallway and the adjacent room. Detectors shall sound an alarm audible in all sleeping areas of the dwelling unit in which they are located.

NFPA 72 
Section No. 29.11.3.4 Specific Location Requirements.
The installation of smoke alarms and smoke detectors shall comply with the following requirements.

This is the end of my references. You can find your specific code books online and I will link them in the research resources index. 

Their are other important items like were on your ceilings you should mount your alarms. I'll use an example we used with our building authority. 

NFPA 72
Section No. 29.11.3.4 Specific Location Requirements.
The installation of smoke alarms and smoke detectors shall comply with the following requirements.

(7) or (8) depending on what version you own.

(8) Smoke alarms and smoke detectors shall not be installed within a 36 in. (910 mm) horizontal path from the supply registers of a forced air heating or cooling system and shall be installed outside of the direct airflow from those registers.

The location came up because we placed one smoke detector within 36" of an air return duct. I researched this and found a NFPA discussion back in 1996 that referenced this location restriction. But I have not seen the same working in any NFPA 72 since 1996. I concluded it was a builders and inspectors rule of thumb but never actually part of the NFPA 72 specific location requirements. 

To appease your local building code enforcement people we opted to move horizontally the 2 smoke detectors 4 feet to cover all out bases. It works out that our 7 Point Rule works even better with the new location. So be flexible when you are looking to cover a large residential home with a large split storage attic that was built using IRC 2015 and 2021 codes. 

More details for locations: NFPA 72

29.8.3 * Smoke Alarms and Smoke Detectors.

Smoke alarms, smoke detectors, devices, combination of devices, and equipment shall be installed in accordance with the manufacturer’s listing and published instructions, and, unless specifically listed for the application, shall comply with requirements in 29.8.3.1 through 29.8.3.4.

29.8.3.1 * Peaked Ceilings.

Smoke alarms or smoke detectors mounted on a peaked ceiling shall be located within 36 in. (910 mm) horizontally of the peak, but not closer than 4 in. (100 mm) vertically to the peak.

29.8.3.2 * Sloped Ceilings.

Smoke alarms or smoke detectors mounted on a sloped ceiling having a rise greater than 1 ft in 8 ft (1 m in 8 m) horizontally shall be located within 36 in. (910 mm) of the high side of the ceiling, but not closer than 4 in. (100 mm) from the adjoining wall surface.

29.8.3.3 * Wall Mounting.

Smoke alarms or smoke detectors mounted on walls shall be located not farther than 12 in. (300 mm) from the adjoining ceiling surface.

29.8.3.4 Specific Location Requirements.

The installation of smoke alarms and smoke detectors shall comply with the following requirements:

1. Smoke alarms and smoke detectors shall not be located where ambient conditions, including humidity and temperature, are outside the limits specified by the manufacturer's published instructions.
2. Smoke alarms and smoke detectors shall not be located within unfinished attics or garages or in other spaces where temperatures can fall below 40ºF (4ºC) or exceed 100ºF (38ºC).
3. Where the mounting surface could become considerably warmer or cooler than the room, such as a poorly insulated ceiling below an unfinished attic or an exterior wall, smoke alarms and smoke detectors shall be mounted on an inside wall.
4. Smoke alarms and smoke detectors shall not be installed within an area of exclusion determined by a 10 ft (3.0 m) radial distance along a horizontal flow path from a stationary or fixed cooking appliance, unless listed for installation in close proximity to cooking appliances. Smoke alarms and smoke detectors installed between 10 ft (3.0 m) and 20 ft (6.1 m) along a horizontal flow path from a stationary or fixed cooking appliance shall be equipped with an alarm-silencing means or use photoelectric detection.
   Exception: Smoke alarms or smoke detectors that use photoelectric detection shall be permitted for installation at a radial distance greater than 6 ft (1.8 m) from any stationary or fixed cooking appliance when the following conditions are met:
   1. The kitchen or cooking area and adjacent spaces have no clear interior partitions or headers and
   2. The 10 ft (3.0 m) area of exclusion would prohibit the placement of a smoke alarm or smoke detector required by other sections of this code.
5. Effective January 1, 2016, smoke alarms and smoke detectors used in household fire alarm systems installed between 6 ft (1.8 m) and 20 ft (6.1 m) along a horizontal flow path from a stationary or fixed cooking appliance shall be listed for resistance to common nuisance sources from cooking.
6. Smoke alarms and smoke detectors shall not be installed within a 36 in. (910 mm) horizontal path from a door to a bathroom containing a shower or tub unless listed for installation in close proximity to such locations.
7. Smoke alarms and smoke detectors shall not be installed within a 36 in. (910 mm) horizontal path from the supply registers of a forced air heating or cooling system and shall be installed outside of the direct airflow from those registers.
8. Smoke alarms and smoke detectors shall not be installed within a 36 in. (910 mm) horizontal path from the tip of the blade of a ceiling-suspended (paddle) fan.
9. Where stairs lead to other occupiable levels, a smoke alarm or smoke detector shall be located so that smoke rising in the stairway cannot be prevented from reaching the smoke alarm or smoke detector by an intervening door or obstruction.
10. For stairways leading up from a basement, smoke alarms or smoke detectors shall be located on the basement ceiling near the entry to the stairs.
11. For tray-shaped ceilings (coffered ceilings), smoke alarms and smoke detectors shall be installed on the highest portion of the ceiling or on the sloped portion of the ceiling within 12 in. (300 mm) vertically down from the highest point.
12. Smoke alarms and detectors installed in rooms with joists or beams shall comply with the requirements of 17.7.3.2.4.
    • 17.7.3.2.4.1 Solid joists shall be considered equivalent to beams for smoke detector spacing guidelines.
13. Heat alarms and detectors installed in rooms with joists or beams shall comply with the requirements of 17.6.3.

29.11 Installation.

29.11.1 General.

29.11.1.1
All equipment shall be installed in accordance with the manufacturer’s published instructions and applicable electrical standards.

Enhanced Content
29.11.1.2
All devices shall be so located and mounted that accidental operation is not caused by jarring or vibration.

29.11.1.3
All equipment shall be mounted so as to be supported independently of its attachment to wires.

29.11.1.4
The supplier or installing contractor shall provide the system owner or other responsible parties with the following:

1. An instruction booklet illustrating typical installation layouts
2. Instruction charts describing the operation, method, and frequency of testing and maintenance of the warning equipment
3. Printed information for establishing an emergency evacuation plan
4. Printed information to inform system owners where they can obtain repair or replacement service, and where and how parts requiring regular replacement, such as batteries or bulbs, can be obtained within 2 weeks
5. Information noting both of the following:
   1. Unless otherwise recommended by the manufacturer's published instructions, smoke alarms shall be replaced when they fail to respond to tests.
   2. Smoke alarms shall not remain in service longer than 10 years from the date of manufacture unless otherwise provided by manufacturer's published instructions.
6. The instructions required in Section 29.14

29.11.2 Interconnection of Multiple-Station Alarms.

29.11.2.1*
The interconnection of alarms shall comply with the following:

1. Alarms shall not be interconnected in numbers that exceed the manufacturer’s published instructions.
2. In no case shall more than 18 initiating devices be interconnected (of which 12 can be smoke alarms) where the interconnecting means is not supervised.
3. In no case shall more than 64 initiating devices be interconnected (of which 42 can be smoke alarms) where the interconnecting means is supervised.
4. Alarms of different manufacturers shall not be interconnected unless listed as being compatible with the specific model.
5. When alarms of different types are interconnected, all interconnected alarms shall produce the appropriate audible response for the phenomena being detected or remain silent.

Enhanced Content

29.11.2.2
A single fault on the interconnecting means between multiple-station alarms shall not prevent single-station operation of any of the interconnected alarms.

29.11.2.3
Remote notification appliance circuits of multiple-station alarms shall be capable of being tested for integrity by activation of the test feature on any interconnected alarm.

Enhanced Content

29.11.2.4
Activation of the test feature shall result in the operation of all interconnected notification appliances.

29.11.3* Smoke Alarms and Smoke Detectors.

Smoke alarms, smoke detectors, devices, combination of devices, and equipment shall be installed in accordance with the manufacturer’s listing and published instructions, and, unless specifically listed for the application, shall comply with requirements in 29.11.3.1 through 29.11.3.4.

Enhanced Content

29.11.3.1* Peaked Ceilings.
Smoke alarms or smoke detectors mounted on a peaked ceiling shall be located within 36 in. (910 mm) horizontally of the peak, but not closer than 4 in. (100 mm) vertically to the peak.

29.11.3.2* Sloped Ceilings.
Smoke alarms or smoke detectors mounted on a sloped ceiling having a rise greater than 1 ft in 8 ft (1 m in 8 m) horizontally shall be located within 36 in. (910 mm) of the high side of the ceiling, but not closer than 4 in. (100 mm) from the adjoining wall surface.

29.11.3.3* Wall Mounting.
Smoke alarms or smoke detectors mounted on walls shall be located not farther than 12 in. (300 mm) from the adjoining ceiling surface.

29.11.3.4 Specific Location Requirements.
The installation of smoke alarms and smoke detectors shall comply with the following requirements:

1. Smoke alarms and smoke detectors shall not be located where ambient conditions, including humidity and temperature, are outside the limits specified by the manufacturer's published instructions.
2. Smoke alarms and smoke detectors shall not be located within unfinished attics or garages or in other spaces where temperatures can fall below 40ºF (4.4ºC) or exceed 100ºF (38ºC).
3. Where the mounting surface could become considerably warmer or cooler than the room, such as a poorly insulated ceiling below an unfinished attic or an exterior wall, smoke alarms and smoke detectors shall be mounted on an inside wall.
4. Smoke alarms and smoke detectors shall not be installed between 10 ft (3.0 m) and 20 ft (6.1 m) along a horizontal flow path from a stationary or fixed cooking appliance unless the devices comply with the following:
   1. Prior to January 1, 2025, smoke alarms and smoke detectors shall be equipped with an alarm silencing means, use photoelectric detection, or be listed for resistance to common nuisance sources from cooking in accordance with the 8th edition of UL 217, Smoke Alarms, the 7th edition of UL 268, Smoke Detectors for Fire Alarm Systems, or subsequent editions.
   2. Effective January 1, 2025, smoke alarms and smoke detectors shall be listed for resistance to common nuisance sources from cooking in accordance with the 8th edition of UL 217, the 7th edition of UL 268, or subsequent editions.
5. Smoke alarms and smoke detectors shall not be installed within an area of exclusion determined by a 10 ft (3.0 m) radial distance along a horizontal flow path from a stationary or fixed cooking appliance. When the 10 ft (3.0 m) area of exclusion would prohibit the placement of a smoke alarm or smoke detector required by other sections of this Code, and when the kitchen or cooking area and adjacent spaces have no clear interior partitions or headers, smoke alarms or smoke detectors shall be permitted for installation at a radial distance between 6 ft (1.8 m) and 10 ft (3.0 m) from any stationary or fixed cooking appliance unless the devices comply with the following:
   1. Prior to January 1, 2025, the devices shall use photoelectric detection or be listed for resistance to common nuisance sources from cooking in accordance with the 8th edition of UL 217, the 7th edition of UL 268, or subsequent editions.
   2. Effective January 1, 2025, the devices shall be listed for resistance to common nuisance sources from cooking nuisance alarms in accordance with the 8th edition of UL 217, the 7th edition of UL 268, or subsequent editions.
6. Smoke alarms and smoke detectors shall not be installed within a 36 in. (910 mm) horizontal path from a door to a bathroom containing a shower or tub unless listed for installation in close proximity to such locations.
7. Smoke alarms and smoke detectors shall not be installed within a 36 in. (910 mm) horizontal path from the supply registers of a forced air heating or cooling system and shall be installed outside of the direct airflow from those registers.
8. Smoke alarms and smoke detectors shall not be installed within a 36 in. (910 mm) horizontal path from the tip of the blade of a ceiling-suspended (paddle) fan unless the room configuration restricts meeting this requirement.
9. Where stairs lead to other occupiable levels, a smoke alarm or smoke detector shall be located so that smoke rising in the stairway cannot be prevented from reaching the smoke alarm or smoke detector by an intervening door or obstruction.
10. For stairways leading up from a basement, smoke alarms or smoke detectors shall be located on the basement ceiling near the entry to the stairs.
11. For tray-shaped ceilings (coffered ceilings), smoke alarms and smoke detectors shall be installed on the highest portion of the ceiling or on the sloped portion of the ceiling within 12 in. (300 mm) vertically down from the highest point.
12. Smoke alarms and detectors installed in rooms with joists or beams shall comply with the requirements of 17.7.4.2.4.
13. Heat alarms and detectors installed in rooms with joists or beams shall comply with the requirements of 17.6.3.

Enhanced Content

29.11.4* Heat Detectors and Heat Alarms.

29.11.4.1*
On smooth ceilings, heat detectors and heat alarms shall be installed within the strict limitations of their listed spacing.

29.11.4.2*
For sloped ceilings having a rise greater than 1 ft in 8 ft (1 m in 8 m) horizontally, the detector or alarm shall be located within 36 in. (910 mm) of the peak.

29.11.4.3
The spacing of additional detectors or alarms, if any, shall be based on a horizontal distance measurement, not on a measurement along the slope of the ceiling.

29.11.4.4*
Heat detectors or alarms shall be mounted on the ceiling at least 4 in. (100 mm) from a wall or on a wall with the top of the detector or alarm not less than 4 in. (100 mm), nor more than 12 in. (300 mm), below the ceiling.

29.11.4.5
Where the mounting surface could become considerably warmer or cooler than the room, such as a poorly insulated ceiling below an unfinished attic or an exterior wall, the detectors or alarms shall be mounted on an inside wall.

29.11.4.6
In rooms with open joists or beams, all ceiling-mounted detectors or alarms shall be located on the bottom of such joists or beams.

29.11.4.7*
Detectors or alarms installed on an open-joisted ceiling shall have their smooth ceiling spacing reduced where this spacing is measured at right angles to solid joists in the case of heat detectors or heat alarms, this spacing shall not exceed one-half of the listed spacing.

29.11.5 Wiring and Equipment.

The installation of wiring and equipment shall be in accordance with the requirements of Article 760 of NFPA 70.

Enhanced Content

29.11.6 Installation and Inspection Record.
Where a form is required by the AHJ to document the installation and inspection of a household alarm system or single- or multiple-station alarms, 7.8.2(3) shall be used to document the record of completion and inspection.

Research Resource: 

• NOTE: You must use your states required code books. In Louisiana currently it's between IRC-2015 and IRC-2021 PLUS NFPA 72 2018 or newer and then consult your State Fire Marshals Office they can and will offer assistance to help you design a system based on state regulations.
• For Louisiana: Louisiana Administrative Code Chapter 55:V:303 
• This code ends the discussion of how to determine a storage attic. Code Notes: Attic and Smoke Alarms Habitable Attic Changed from IRC-2009 to IRC-2015
• Habitable Attic Egress Requirements: A pull down stair is not compliant with the habitable attic required egress, even if the space is intended to remain unfinished or is labeled as unfinished storage space.
• Section 704 Fire Prevention Systems only for a reading reference for better understanding.
• • Smoke Detector / Alarm located near HVAC Return Duct is your choice and not regulated by IRC, ICC or NFPA so don't follow discussions that say you "CAN NOT" unless they show you in the actual CODE. (Example discussion that is incorrect and not referencing any codes that have been related to the subject since 1996.)
• 2022 NFPA 72 National Fire Alarm and Signaling Code
• Parameter study conducted concerning smoke movement in response to HVAC induced airflows from slot diffusers, slot returns, &;;; rectangular returns.
• 29.11.3.4 Specific Location Requirements. Public Input No. 583-NFPA 72-2019 [ Section No. 29.11.3.4 ] Nov. 2019
• Buy your code book ICC / IRC
• Follow your local NEWS RELEASE OFFICE OF LOUISIANA STATE FIRE MARSHAL
• Codes, Rules &;;; Laws Enforced by The Louisiana State Fire Marshal 

Builders, Designers, Electricians, Homeowners and Handyman service providers.
Get it right the first time, you may not have a second chance.
NFPA+ICC+IRC+State Fire Marshal
Read your codes and go beyond.