Residential Remodeling (B-2) · Lesson 3 of 5

Smoke and CO Alarm Upgrades Triggered by a Remodel

"Smoke and CO Alarm Upgrades Triggered by a Remodel" is lesson 3 of 5 in the Residential Remodeling (B-2) Learning Hub. It opens with "A Permit Pulls the Whole House Up to New-Dwelling Smoke Alarm Rules" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. A Permit Pulls the Whole House Up to New-Dwelling Smoke Alarm Rules
  2. Where Smoke Alarms Go (R310.3)
  3. Interconnection and Power (R310.4, R310.6)
  4. Where CO Alarms Go (R311.3)
  5. Count Level by Level

The worked example in the course applies this lesson to a realistic job in 7 steps, from "Check the trigger" through "Combine where locations match".

What you'll be able to do

  • Explain the main idea of "Smoke and CO Alarm Upgrades Triggered by a Remodel" in plain language you can use on the exam.
  • Apply this step with confidence: "Interconnection and Power (R310.4, R310.6)".
  • Apply this step with confidence: "Where CO Alarms Go (R311.3)".
  • Apply this step with confidence: "Count Level by Level".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Remodel Alarm Count, Level by Level UPPER LEVEL BEDROOM 1BEDROOM 2BEDROOM 3 HALL SSSS+CO MAIN LEVEL (no bedrooms) LIVING / KITCHEN S+CO BASEMENT (new bedroom, gas furnace) NEW BEDROOM FURNACE ROOM HALL SS+CO ALARM COUNT smoke alarm (S) S+CO combo SMOKE (R310.3) Bedrooms: 3 + 1 = 4 Outside sleeping areas: 2 halls = 2 Other level without one: main = 1 Smoke total = 4 + 2 + 1 = 7 CO (R311.3) Outside sleeping areas: 2 halls = 2 Other occupiable level: main = 1 CO total = 2 + 1 = 3 3 spots need both, so use combos: 4 smoke + 3 combos = 7 devices 7 DEVICES: 4 BEDROOM SMOKE ALARMS + 3 SMOKE/CO COMBINATION ALARMS Smoke alarms interconnected (R310.4); CO alarms outside each sleeping area and on every level (R311.3) Source: 2025 California Residential Code R310.2-R310.4 (smoke alarms) and R311.2-R311.3 (carbon monoxide alarms) CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: A Permit Pulls the Whole House Up to New-Dwelling Smoke Alarm Rules

Under 2025 California Residential Code (CRC) R310.2.2, where alterations, repairs or additions requiring a permit occur, the individual dwelling unit must be equipped with smoke alarms located as required for new dwellings. Carbon monoxide alarms have their own triggers: R311.2.1 requires them in dwelling units that contain a fuel-fired appliance or fireplace, or have an attached garage with an opening into the dwelling, and R311.2.2 requires new CO alarms when an addition is made or a fuel-burning heater, appliance or fireplace is added. Exterior-surface work (roofing, siding, windows and doors, a porch or deck) and plumbing work are exceptions in R311.2.2 (and in the interconnection and power rules). Plan the alarms in the estimate, because the inspector will count them.

Step 2: Where Smoke Alarms Go (R310.3)

R310.3 requires smoke alarms in each sleeping room, outside each separate sleeping area in the immediate vicinity of the bedrooms, and on each additional story of the dwelling unit, including basements and habitable attics but not crawl spaces or uninhabitable attics. R310.3 also keeps alarms at least 3 feet horizontally from the door of a bathroom with a tub or shower unless that would prevent placing a required alarm. A hall alarm on a level counts as that level's alarm, so you only add a separate alarm on a story that has neither a bedroom nor a sleeping-area hall.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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