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Does a remodel require you to add smoke and carbon monoxide alarms?

It can, if the work needs a permit. In our reading of Sections R314.2.2 and R315.2.2 of the 2021 International Residential Code, a permitted remodel can require smoke and carbon monoxide alarms placed as in a new home, unless a listed exception applies. Both sections are quoted below in their own words.

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

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By InstaBids editorial team with AI research agents. Sources read: 22 October 2026 Updated 2026-10-22

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Key facts

What does the model code say about smoke alarms in a remodel?

Yes, where the work requires a permit and is not in one of two listed exceptions. Section R314.2.2 of the 2021 International Residential Code is quoted below in its own words, with both exceptions and the list of alarm locations it points to.

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

2021 International Residential Code, Section R314.2.2 (Alterations, repairs and additions), read 22 October 2026: "Where alterations, repairs or additions requiring a permit occur, the individual dwelling unit shall be equipped with smoke alarms located as required for new dwellings."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

The two exceptions of Section R314.2.2, read 22 October 2026: "Work involving the exterior surfaces of dwellings, such as the replacement of roofing or siding, the addition or replacement of windows or doors, or the addition of a porch or deck." "Installation, alteration or repairs of plumbing or mechanical systems."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

Section R314.3, read 22 October 2026, lists where the alarms go. Its first three items: "Smoke alarms shall be installed in the following locations:" "In each sleeping room." "Outside each separate sleeping area in the immediate vicinity of the bedrooms." "On each additional story of the dwelling, including basements and habitable attics and not including crawl spaces and uninhabitable attics."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

In our reading, a permitted kitchen or bathroom remodel that goes beyond plumbing or mechanical work is in neither exception, while replacing roofing or siding, or adding or replacing windows or doors, is in the first.

When does a remodel bring in carbon monoxide alarms too?

When the work requires a permit, is not in one of three listed exceptions, and the home meets a new-construction condition. Section R315.2.2 uses the same permit wording as the smoke alarm section, and Section R315.2.1 names two conditions for new construction; both are quoted below, with all three exceptions.

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

2021 International Residential Code, Section R315.2.2, read 22 October 2026: "Where alterations, repairs or additions requiring a permit occur, the individual dwelling unit shall be equipped with carbon monoxide alarms located as required for new dwellings."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

The three exceptions of Section R315.2.2, read 22 October 2026: "Work involving the exterior surfaces of dwellings, such as the replacement of roofing or siding, or the addition or replacement of windows or doors, or the addition of a porch or deck." "Installation, alteration or repairs of plumbing systems." "Installation, alteration or repairs of mechanical systems that are not fuel fired."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

Section R315.2.1, for new construction, read 22 October 2026: "For new construction, carbon monoxide alarms shall be provided in dwelling units where either or both of the following conditions exist." "The dwelling unit contains a fuel-fired appliance." "The dwelling unit has an attached garage with an opening that communicates with the dwelling unit."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

Section R315.3, read 22 October 2026, on where they go: "Carbon monoxide alarms in dwelling units shall be installed outside of each separate sleeping area in the immediate vicinity of the bedrooms. Where a fuel-burning appliance is located within a bedroom or its attached bathroom, a carbon monoxide alarm shall be installed within the bedroom."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

In our reading, the smoke alarm exceptions leave out all mechanical work, but the carbon monoxide exceptions leave out only mechanical work that is not fuel fired, so a permitted gas furnace or gas water heater swap can bring in carbon monoxide alarms without bringing in smoke alarms.

Do the alarms have to be hardwired and linked together?

Not always. The power source sections of R314 and R315 each allow battery power for alarms added under the remodel sections, and R315.5 has an exception on linking carbon monoxide alarms in existing areas; the texts are quoted below, with the CPSC's safety advice on the same points.

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).
Source: U.S. Consumer Product Safety Commission, Carbon Monoxide Information Center, read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

Exception 2 of Section R314.6 and Exception 2 of Section R315.6, read 22 October 2026: "Smoke alarms installed in accordance with Section R314.2.2 shall be permitted to be battery powered." "Carbon monoxide alarms installed in accordance with Section R315.2.2 shall be permitted to be battery powered."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

The exception in Section R315.5, read 22 October 2026: "Interconnection of carbon monoxide 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 interconnection without the removal of interior finishes."

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

CPSC, Carbon Monoxide Information Center, read 22 October 2026: "Install battery-operated CO alarms or CO alarms with battery backup on every level of the home and outside sleeping areas. Interconnected CO alarms are best; when one sounds, they all sound."

Source: U.S. Consumer Product Safety Commission, Carbon Monoxide Information Center, read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

The U.S. Consumer Product Safety Commission's page quoted above is safety advice, not a building rule. In our reading, open walls and ceilings during a remodel are the moment your local building department may expect wiring and linking, so ask before the drywall goes back up.

Which remodels and jurisdictions use these alarm rules?

In our reading, not under the model code by itself. Both alarm sections quoted above turn on whether the work requires a permit, and Section R105.2 lists finish work that needs no permit; its words are quoted below.

Source: International Code Council, 2021 International Residential Code, Chapter 3 Building Planning (Sections R314 and R315), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).
Source: International Code Council, 2021 International Residential Code, Chapter 1 Scope and Administration (Sections R101.1 and R105.2), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

2021 International Residential Code, Section R105.2 (Work exempt from permit), read 22 October 2026: "Permits shall not be required for the following:" Item 6 of its building list: "Painting, papering, tiling, carpeting, cabinets, counter tops and similar finish work."

Source: International Code Council, 2021 International Residential Code, Chapter 1 Scope and Administration (Sections R101.1 and R105.2), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

In our reading, new cabinets and counter tops alone do not reach the alarm sections under the model code, but the same kitchen job with new wiring, moved plumbing or walls taken out may need a permit, and then it does. Your local code decides.

Only your local code answers that. Section R101.1 of the IRC leaves a blank for the name of the place that adopts it, and a state can set alarm rules for every home, remodel or not; Minnesota is quoted below as one example.

Source: International Code Council, 2021 International Residential Code, Chapter 1 Scope and Administration (Sections R101.1 and R105.2), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).
Source: Minnesota Statutes 299F.51, Requirements for carbon monoxide alarms, Office of the Revisor of Statutes, read 22 October 2026.
Source: Minnesota Statutes 299F.362, Smoke alarms, Office of the Revisor of Statutes, read 22 October 2026.

2021 International Residential Code, Section R101.1 (Title), read 22 October 2026: "These provisions shall be known as the Residential Code for One- and Two-family Dwellings of [NAME OF JURISDICTION], and shall be cited as such" The chapter's user note adds: "The one- and two-family dwelling code is intended to be adopted as a legally enforceable document, and it cannot be effective without adequate provisions for its administration and enforcement."

Source: International Code Council, 2021 International Residential Code, Chapter 1 Scope and Administration (Sections R101.1 and R105.2), read 22 October 2026 (our saved browser copy, as read on 2026-10-22).

Minnesota Statutes 299F.51, subdivision 1, read 22 October 2026: "(a) Every single-family dwelling and every dwelling unit in a multifamily dwelling must have an approved and operational carbon monoxide alarm installed within ten feet of each room lawfully used for sleeping purposes."

Source: Minnesota Statutes 299F.51, Requirements for carbon monoxide alarms, Office of the Revisor of Statutes, read 22 October 2026.

Minnesota Statutes 299F.362, subdivision 3, read 22 October 2026: "Every dwelling unit within a dwelling must be provided with a smoke alarm meeting the requirements of the State Fire Code."

Source: Minnesota Statutes 299F.362, Smoke alarms, Office of the Revisor of Statutes, read 22 October 2026.

Other states and cities adopt different code editions, add their own amendments or have their own alarm laws, which this page does not quote.

How do you plan alarms into your remodel bids?

Find out what your building department expects before you collect bids, then make every bid price the same alarm work. This is practical reasoning, not legal advice and not a finding from any agency.

  1. Ask your city or county building department which residential code edition it enforces, and whether it amended the smoke and carbon monoxide alarm sections.
  2. Ask whether your project needs a permit at all, and note which parts of the job (wiring, gas lines, walls coming out) are the reason.
  3. List each bedroom, the hallway outside the bedrooms, each floor and the basement, and mark where alarms are now.
  4. Note every gas, oil or wood burning appliance and whether the garage is attached, since the new-construction conditions quoted above name both.
  5. Write into your request that each bid must say how many smoke and carbon monoxide alarms it adds, where they go, and whether they are hardwired, battery powered or linked.
  6. Keep the final inspection record with your house papers.

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Source: InstaBids process and privacy, live-page excerpts, read 22 October 2026.

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