How to Mark Up a Floor Plan for Required Alarm Locations

Why this matters

When a job triggers alarm work, the quote either names every alarm the house needs or it does not, and the gap shows up at final inspection as a return trip nobody priced. The same sketch, used at the end of the job, is the fastest way to confirm that every alarm that was on the ceiling when you arrived is back, working, and in a place the code allows. Ten minutes with a pencil prevents both failures, and it gives the office a document it can attach to the estimate and the homeowner a picture of why the number is what it is.

This card is the method. Which work triggers the alarm requirements on an existing house is in 'Smoke and CO Alarm Requirements Your Permit Triggers'; the sensing types and the exact cooking distances belong to their own sibling cards. The rule locations below are from the 2021 IRC, R314 and R315, as adopted by your jurisdiction; local amendments can add locations.

The steps

1. Sketch the house with every door and the use of every room. It does not need to be to scale, but it needs every wall, every door, every stair and the use of each room written in it. Alarm rules are written around rooms and the doors between them: "each sleeping room", "outside each separate sleeping area", "from the door of a bathroom." A sketch without doors cannot answer any of those. Skip it and you will mark an alarm in a hallway without noticing that a bathroom door opens right under it.

2. Mark every sleeping room, by how it is used. A sleeping room is any room used for sleeping, not just the rooms the listing called bedrooms. Ask the homeowner which rooms people sleep in, including an office with a pullout couch or a finished basement room a teenager uses. Each one gets a smoke alarm inside it under R314.3. Miss one and the quote is short an alarm and a run of interconnect wire, and the inspector who sees a bed in that room will say so.

3. Group the sleeping rooms into sleeping areas and mark one alarm outside each. R314.3 requires a smoke alarm outside each separate sleeping area, in the immediate vicinity of the bedrooms. A sleeping area is a group of bedrooms that share a hallway or common space. Three bedrooms off one hall make one area; a primary suite on the far side of the living room is a second area. The alarm goes in the hall or space the bedroom doors open onto, where smoke from the rest of the house would pass before it reached them. The common error is one hall alarm for a house that has two sleeping areas, which leaves the separate suite with only its own bedroom alarm.

4. Mark at least one alarm on every story, including the basement and any habitable attic. R314.3 requires one on each additional story, including basements and habitable attics, but not crawl spaces or uninhabitable attics. A basement alarm is commonly placed near the foot of the stair, where smoke from below reaches first on its way up. A story with no bedrooms still needs one. Skip this and the basement, which is where the furnace, the water heater, the dryer and the electrical panel usually are, is the one floor with no warning.

5. Decide whether CO alarms are triggered, then mark them. Under R315, carbon monoxide alarms are required where the house has a fuel-burning appliance or an attached garage with an opening into the dwelling, subject to the exceptions in that section. Where triggered, mark one outside each separate sleeping area in the immediate vicinity of the bedrooms, and one inside any bedroom that has a fuel-burning appliance in it or in its attached bathroom. Write the trigger on the sketch ("gas furnace and water heater in basement"), because the trigger is what a reviewer will ask about. Where you mark a location the code does not require but the alarm manufacturer or the local fire department recommends, label it "recommended" so the quote does not present it as mandatory. Exact CO locations and their exceptions are in 'Where a House Needs CO Alarms Under the 2021 IRC'.

6. Run the clearance checks on every mark. Three checks, each of which can move a mark you have already drawn:

• Bathrooms. R314.3 keeps a smoke alarm at least 3 ft horizontally from the door or opening of a bathroom that contains a bathtub or shower, unless that would prevent placing a required alarm. Steam sets off smoke alarms; this rule exists for that. A powder room with no tub or shower is not covered by it.
• Cooking appliances. R314.3.1 sets minimum horizontal distances from a permanently installed cooking appliance that depend on the alarm's sensing type. Measure from the range to every nearby mark and write the distance on the sketch; which type is allowed at that distance is in 'Smoke Alarm Distances From Cooking Appliances and Bathrooms'.
• Air movement and the manufacturer. Supply registers, return grilles and ceiling fans can blow smoke away from an alarm, and the alarm's installation instructions set distances from them and from ceiling peaks and wall corners. Note any mark that sits near one.

Skip this step and you install an alarm in a spot the clearance rules or the instructions do not allow, and it will either fail inspection or nuisance-alarm until someone takes it down.

7. Count the marks and note interconnection and power. Under R314.4, where more than one smoke alarm is required, they must be interconnected so that one sounding sets off all of them; R315 has a matching rule for CO alarms. Write the total of smoke marks and CO marks, whether existing alarms are hardwired, battery or sealed long-life, and which rooms have a ceiling or attic the interconnect wiring can reach. Power and interconnect requirements on an existing house depend on what the work exposes, which is the permit card's subject. The count is what the office prices, and what the end-of-job check compares against.

Worked example: three bedrooms, two sleeping areas and a basement

A single-story house with a full unfinished basement is getting a kitchen remodel under permit, which in this jurisdiction triggers alarm upgrades throughout. Two bedrooms and a hall bath with a tub sit off a west hall. The primary bedroom, with an ensuite shower, opens off a short east hall on the far side of the living room; that hall also has a powder room with only a toilet and sink. The gas furnace and gas water heater are in the basement. There is no attached garage and no attic space anyone uses.

 MAIN FLOOR (one story)
 +----------+----------+----------+----------+
 | BR2      | BR3      | KITCHEN  | BR1      |
 | SMK      | SMK      | range    | SMK      |
 |          |          |          | ensuite  |
 +---door---+---door---+          | w/shower |
 | WEST HALL SMK + CO  | LIVING   +---door---+
 | hall bath (tub)     |          | EAST HALL|
 | bath door 4 ft away |          | SMK + CO |
 +---------------------+----------+ powder rm|
                                  +----------+
 BASEMENT (unfinished)
 +-------------------------------------------+
 | stair foot: SMK   furnace   water heater  |
 +-------------------------------------------+

Smoke alarms, step by step.

• Step 2, sleeping rooms: BR1, BR2 and BR3, one each. 3 alarms.
• Step 3, sleeping areas: the west hall serves BR2 and BR3; the east hall serves BR1. Two separate areas, one alarm outside each. 2 alarms.
• Step 4, stories: the main floor is already covered by the alarms above; the basement needs its own, at the foot of the stair. 1 alarm.
• Total: 3 + 2 + 1 = 6 smoke alarms.

CO alarms. Step 5: triggered, because there are fuel-burning appliances (the furnace and water heater). One outside each of the two sleeping areas: 2 CO alarms, sharing the west hall and east hall locations as combination units or as separate devices. No bedroom has a fuel appliance in it or its bath, so no bedroom CO alarm is required. The basement holds both fuel appliances but no sleeping room, so R315 does not require one there; the homeowner wants one anyway, and it goes on the sketch labeled "recommended, not required," placed at the distance from the appliances that the alarm's instructions give.

Clearance checks, step 6.

• West hall smoke alarm: first drawn at 2 ft from the hall bath door. The hall bath has a tub, so the 3 ft rule applies, and 2 ft fails. Moved down the hall to 4 ft from the door, which still sits outside both bedroom doors. Passes.
• BR1 smoke alarm: first drawn 2 ft from the ensuite door. The ensuite has a shower, so the rule applies again; moved to 4 ft, near the center of the bedroom ceiling. Passes.
• East hall smoke alarm: sits beside the powder room door, but the powder room has no tub or shower, so the 3 ft rule does not apply to it. Passes as drawn.
• Cooking: the range is measured at about 15 ft from the west hall alarm and about 12 ft from the east hall alarm, both written on the sketch so the alarm type for each can be checked against the cooking-distance card.

Two of the six smoke marks moved during step 6. That is normal, and it is why the clearance pass comes before anyone drills a hole.

Step 7, the count on the quote. 6 smoke alarm locations, 2 required CO locations and 1 recommended, interconnected, with the kitchen ceiling open during the remodel giving a path for the interconnect to both halls. The existing house had 3 smoke alarms (BR2, the west hall and the basement) and no CO alarms, so the quote covers 3 new smoke locations, 2 required CO, 1 recommended CO, and replacement or reconnection of the existing 3 as the permit card requires.

Using the same sketch at the end of the job

Before anyone leaves the final day, take the sketch through the house. At each mark, confirm there is an alarm, it is the type the quote named, its cover is off and its dust protection removed, and it responds to its test button; then, where they are interconnected, press test on each alarm in turn and confirm every other one sounds, because one unit passing proves only that it sends. If a mark has no alarm, or an alarm is still bagged, the job is not finished. Where a homeowner declined an alarm the quote included, write that on the sketch and on the work order. See 'The End-of-Job Life-Safety Check SOP' and 'How to Test a Home's Alarms Correctly'.

References

• 2021 International Residential Code, Sections R314 (smoke alarms) and R315 (carbon monoxide alarms), as adopted and amended by your jurisdiction.
• The alarm manufacturer's installation instructions, for distances from air movement, ceiling peaks, corners and fuel-burning appliances.
• See related: Smoke and CO Alarm Requirements Your Permit Triggers.
• See related: Smoke Detector Placement + Types Reference.
• See related: Where a House Needs CO Alarms Under the 2021 IRC.