Smoke and CO Alarm Requirements for Remodels
Applies to one- and two-family dwellings. The model code is a baseline; your state or city may adopt a different edition or add rules, so confirm with your building department before you rely on any single number here.
If your remodel needs a permit, the building code can require you to add smoke and carbon monoxide alarms to the whole house, not just the room you are working in. Under the 2024 International Residential Code, any permitted alteration, repair, or addition requires the dwelling unit to have alarms placed as they would be in a new home. That surprises people who only open up a kitchen or finish a basement.
The rule has real exceptions, and they are not symmetrical. Exterior work such as roofing, siding, windows, doors, a porch, or a deck is exempt for both kinds of alarm. Plumbing work is exempt for both. Mechanical work is exempt from the smoke alarm trigger, but for carbon monoxide the 2024 code exempts only mechanical systems that are not fuel fired, so replacing a furnace or gas water heater under permit does not get you out of the CO alarm requirement.
The code also makes retrofits easier than new construction: alarms installed under the alteration trigger may be battery powered, and listed wireless alarms satisfy the interconnection rule. States then layer their own rules on top, including resale certificates, sealed 10-year batteries, and seller duties. This page covers the model-code rules in detail and the states we have been able to verify against state sources.
Finishing a basement is a permitted alteration, so it triggers whole-house smoke and CO alarms; plan for them when you scope the project. Free, no signup.
What Triggers Alarms in a Remodel (2024 IRC R310.2.2 and R311.2.2)
Both sections open with the same sentence: where alterations, repairs, or additions requiring a permit occur, the individual dwelling unit shall be equipped with alarms located as required for new dwellings. The difference is in the exceptions. Smoke alarms exempt exterior work and all plumbing or mechanical work. Carbon monoxide alarms exempt exterior work, plumbing work, and only mechanical work that is not fuel fired. In practice, a permitted gas furnace, boiler, or water heater replacement triggers CO alarms under the 2024 text but does not trigger smoke alarms.
| Work under permit | Smoke alarms (R310.2.2) | CO alarms (R311.2.2) |
|---|---|---|
| Kitchen, bath, basement finish, addition, or other interior alteration | Required | Required |
| Roofing, siding, window or door replacement, porch or deck | Exempt | Exempt |
| Plumbing installation, alteration, or repair | Exempt | Exempt |
| Mechanical work that is not fuel fired (e.g. electric heat pump, ductwork) | Exempt | Exempt |
| Fuel-fired mechanical work (gas furnace, boiler, gas water heater) | Exempt | Required |
Check Your Edition: R314/R315 vs. R310/R311
The sections were renumbered in the 2024 IRC. In the 2018 and 2021 editions, smoke alarms are in R314 and carbon monoxide alarms are in R315, and the alteration trigger sits at R314.2.2 and R315.2.2. Many jurisdictions still enforce the 2018 or 2021 edition, and a state can amend the text, so the exact exception wording for fuel-fired mechanical work can differ from what is shown above. Ask which edition and amendments apply to your permit date.
Where the Alarms Go (2024 IRC R310.3 and R311.3)
Smoke alarms go in each sleeping room, outside each separate sleeping area in the immediate vicinity of the bedrooms, and on each additional story including basements and habitable attics (crawl spaces and uninhabitable attics do not count). Two placement rules catch people out: alarms must be at least 3 feet horizontally from the door or opening of a bathroom with a tub or shower, unless that would block a required location, and at least 10 feet horizontally from a permanently installed cooking appliance, reduced to 6 feet only where needed to satisfy the other location rules. A room open to a bedroom hallway whose ceiling is 24 inches or more higher than the hallway ceiling also needs an alarm in the hallway and in that room. CO alarms go outside each separate sleeping area near the bedrooms, and inside the bedroom if a fuel-burning appliance is in the bedroom or its attached bathroom.
| Location rule | Smoke alarm | CO alarm |
|---|---|---|
| Each sleeping room | Required | Only if a fuel-burning appliance is in the bedroom or its bath |
| Outside each sleeping area, near the bedrooms | Required | Required |
| Each additional story, incl. basements and habitable attics | Required | Not specified by section; located per R311.3 |
| Distance from bathroom with tub or shower | At least 3 ft horizontally | Not specified |
| Distance from a permanent cooking appliance | At least 10 ft (6 ft where needed for required locations) | Not specified |
Power and Interconnection: What a Retrofit Can Get Away With
New construction needs alarms powered from the house wiring with battery backup. Alarms installed under the alteration trigger are allowed to be battery powered (R310.6 Exception 2 and R311.6 Exception 2). When more than one alarm is required, they must be interconnected so one alarm sounds all of them, but physical wiring is not required when listed wireless alarms are used and all alarms sound together. For CO alarms there is a further relief: interconnection is not required in existing areas where the work does not remove interior wall or ceiling finishes and expose the structure, unless an attic, crawl space, or basement gives access for the wiring without tearing finishes out. The 2024 smoke alarm section has no matching exception, so smoke alarms rely on the wireless option.
When CO Alarms Are Required at All
In new construction, a dwelling unit needs CO alarms if it contains a fuel-fired appliance or has an attached garage with an opening that communicates with the dwelling. An all-electric house with a detached garage does not trigger the new-construction rule. The remodel trigger above is separate: once you do permitted interior work (or fuel-fired mechanical work), the CO rule applies as for new dwellings. Combination smoke and CO alarms are allowed in place of either type. Listings are UL 217 for smoke alarms and UL 2034 for CO alarms, and both must be installed per the listing and the manufacturer instructions.
States With Their Own Rules (Statutes Cited)
These states add something to the model code: a resale certificate, a battery requirement, a rule for remodels, or a CO statute that reaches existing homes. Each row cites the state statute, rule, or agency source it came from; some state sites block automated checks, so confirm the current text. Many other states follow the model code as adopted locally, but we have not verified them, so they are not listed. Statutes change, so confirm with your fire marshal or building department.
| State | What is different | Source |
|---|---|---|
| California | Smoke alarms required in existing dwellings and installed per manufacturer instructions; CO alarms required in existing homes with a fossil-fuel appliance, fireplace, or attached garage; battery-only alarms must have a 10-year battery | Health & Safety Code §13113.7, §17926; SB 1394 (2012) |
| Colorado | CO alarm within 15 ft of each sleeping-room entrance on sale or transfer, and when permitted alterations or fuel-fired appliance replacement occur, in homes with a fuel-fired appliance, fireplace, or attached garage | C.R.S. 38-45-101 et seq. (HB 09-1091) |
| Florida | For repairs and level 1 alterations, 10-year sealed-battery alarms may be used instead of hardwiring; a battery alarm newly installed in a level 1 alteration must have a 10-year non-removable battery | F.S. §553.883 |
| Illinois | Alarm within 15 ft of every sleeping room and CO alarm within 15 ft of every sleeping room; new battery alarms must be 10-year sealed since 1/1/2023, while older alarms may stay until 10 years old or failure | 425 ILCS 60; 430 ILCS 135 |
| Maryland | Existing one- and two-family homes: alarms over 10 years old or failing must be replaced, and at a change of tenant; where battery alarms are allowed they must be sealed, tamper resistant, with a hush button | Public Safety §9-104 |
| Massachusetts | Fire department Certificate of Compliance for smoke and CO alarms at sale or transfer; certificate expires 60 days after issue | M.G.L. c.148 §26F, §26F½; 527 CMR 1.00 |
| New Jersey | Smoke, CO, and fire extinguisher certificate before sale, lease, or change of occupancy, valid six months; single-station battery smoke alarms must be 10-year sealed since 1/1/2019 | N.J.A.C. 5:70-2.3; N.J.S.A. 52:27D-133.3 |
| New York | Amanda's Law requires CO alarms in one- and two-family homes with a fuel-burning appliance or attached garage; new and replacement smoke alarms sold in the state must be hardwired or 10-year sealed battery (a retail sale rule) | Executive Law §378(5-a); Dept. of State consumer notice (2019) |
| Pennsylvania | For one- and two-family alterations, repairs, and additions, interconnection does not apply and non-interconnected battery alarms are installed; CO alarms at sale are a seller disclosure, not an install mandate | 34 Pa. Code §403.21(a)(7); Act 121 of 2013 |
| Texas | No statewide residential alarm rule found for owner-occupied homes; the city or county code governs. Landlords have separate duties | Property Code §92.255 (rentals) |
| Washington | CO alarms required; pre-2009 owner-occupied homes were exempt until sale, when the seller must install them before the buyer occupies | RCW 19.27.530 |
Common Misconceptions About State Rules
Several widely repeated claims overstate the law. Illinois does not require every home to have 10-year sealed alarms: the state fire marshal says the requirement is for newly installed battery alarms, and older alarms can stay until they are 10 years old or fail. Florida ties its sealed-battery requirement to level 1 alterations, not every replacement. Maryland's statute requires sealed units only where battery alarms are permitted, not in every home. Pennsylvania does not require CO alarms in every single-family home; the 2013 act requires the seller to disclose whether they are installed. New York's 10-year rule governs what can be sold, and existing alarms do not have to be removed. If a page tells you your state requires something in every home, check it against the statute.
How Long Alarms Last
Smoke alarms wear out. The standard guidance, reflected in NFPA 72 for one- and two-family dwellings, is to replace a smoke alarm when it fails testing or after 10 years from the date of manufacture, unless the manufacturer says otherwise. CO alarms have their own end-of-life signal and date, and combination alarms follow whichever comes first. Maryland and Illinois write 10-year replacement into law for existing alarms; elsewhere it is manufacturer guidance and an inspector or insurer question. Check the manufacture date printed on the back of every alarm before an inspection.
Standards & Citations
| Standard | Code / Section | Requirement |
|---|---|---|
| Smoke Alarms, Alterations, Repairs and Additions | 2024 IRC R310.2.2 | A permitted alteration, repair, or addition requires smoke alarms located as for new dwellings; exterior work and plumbing or mechanical work are exempt. |
| CO Alarms, Alterations, Repairs and Additions | 2024 IRC R311.2.2 | Same trigger for CO alarms; exempts exterior work, plumbing, and mechanical systems that are not fuel fired. |
| Smoke Alarm Location and Power | 2024 IRC R310.3, R310.4, R310.6 | Sleeping rooms, outside sleeping areas, each story; 3 ft from bathroom doors and 10 ft from cooking appliances; interconnected or listed wireless; battery power allowed for alteration retrofits. |
| CO Alarm Location, Interconnection and Power | 2024 IRC R311.3, R311.5, R311.6 | Outside each sleeping area; interconnection relief in existing areas where finishes are not opened; battery power allowed for alteration retrofits. |
Apply These Requirements
Open a calculator to run this guide’s requirements against your own project.
Basement Remodel Calculator
Finishing a basement is a permitted alteration, so it triggers whole-house smoke and CO alarms; plan for them when you scope the project.
Kitchen Remodel Calculator
A permitted kitchen remodel triggers alarms, and the 10-foot cooking-appliance distance affects where the smoke alarm can go.
Home Addition Cost Calculator
An addition is an alteration under the code and needs alarms located as for new dwellings.
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Frequently Asked Questions
Do I need to add smoke detectors if I remodel?
If the work requires a permit, yes. Under the 2024 IRC, a permitted alteration, repair, or addition requires the dwelling unit to have smoke alarms located as required for new dwellings. Exterior work such as roofing, siding, windows, doors, a porch, or a deck is exempt, as is plumbing or mechanical work. Unpermitted work does not trigger the code rule, but it can cause problems at resale and with insurers.
Does replacing a furnace or water heater require CO alarms?
Under the 2024 IRC, probably yes if the equipment is fuel fired. The CO alarm exception covers plumbing and mechanical systems that are not fuel fired, so a permitted gas furnace, boiler, or gas water heater replacement is not exempt. The smoke alarm section exempts all plumbing and mechanical work. Older editions (R315.2.2) and some states are worded differently, so confirm your local edition.
Can I use battery-powered alarms in a remodel?
The model code allows it. Alarms installed under the alteration trigger may be battery powered, and listed wireless alarms satisfy the interconnection rule if all alarms sound together. Some states are stricter or looser: Pennsylvania, for example, requires non-interconnected battery alarms in one- and two-family alterations. Always check with your building department.
Where can I not put a smoke alarm?
The 2024 IRC requires smoke alarms at least 3 feet horizontally from the door or opening of a bathroom with a tub or shower, and at least 10 feet horizontally from a permanently installed cooking appliance. The cooking distance can be reduced to 6 feet only where necessary to place an alarm in a required location. Always follow the manufacturer instructions too.
Do I need a certificate to sell my house?
In some states, yes. Massachusetts requires a fire department Certificate of Compliance at sale or transfer (it expires 60 days after issue), and New Jersey requires a smoke, CO, and fire extinguisher certificate before sale, lease, or change of occupancy (valid six months). Washington requires sellers to install CO alarms before a buyer occupies. Most other states are not covered on this page, so ask your local fire department.
Do all states require 10-year sealed battery alarms?
No. Several states have rules, but they are narrower than many summaries say. Illinois requires them for newly installed battery alarms, Florida ties the requirement to level 1 alterations, and New York's 2019 rule governs alarms sold in the state. Maryland requires sealed units where battery alarms are allowed. Check the statute for your state.
Where do these requirements come from?
The 2024 IRC sections were read directly from the International Code Council's digital code site. State rows are limited to claims tied to a state statute, rule, or agency page, and we list the section for each one. States not listed here have not been verified against state sources.
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