In short
- A barndominium smoke and CO alarm calculator counts three smoke locations under model-code IRC R314.3: every sleeping room, outside each separate sleeping area, and each additional story (basements and habitable attics count).
- Carbon monoxide alarms (R315) are needed only if the home has a fuel-fired appliance or an attached garage or shop that opens into it. They go outside each sleeping area, plus inside a bedroom that holds a fuel-burning appliance.
- More than one alarm of either type must be interconnected; listed wireless alarms qualify.
- A 4-bedroom, one-story plan with 2 sleeping areas, a gas furnace and an attached shop needs at least 6 smoke and 2 CO alarms.
This barndominium smoke and CO alarm calculator is for Tyler and Smith County owners who want to know how many alarms their floor plan needs before the electrical rough-in. Enter the stories, bedrooms and sleeping areas, then say whether there is a fuel-fired appliance or an attached garage or shop. It gives the model-code minimum counts and the interconnection rule. Shops that share a wall with the living space are covered in our shop planning guide; bedroom escape windows have their own egress window checker.
En español: calculadora de alarmas de humo y monóxido de carbono
| Sleeping areas | Smoke | CO |
|---|
Example: 1 story, 4 bedrooms, 2 sleeping areas, gas furnace outside the bedrooms, attached shop.
How the numbers are worked out
- Smoke: sleeping rooms.
One alarm in each bedroom: 4.
- Smoke: outside sleeping areas.
One in the immediate vicinity of each separate sleeping area: 2.
- Smoke: extra stories.
One on each additional story, basement or habitable attic. One floor and no basement: 0. Total smoke: 4 + 2 + 0 = 6.
- Carbon monoxide: is it required?
Yes, there is a gas furnace and an attached shop with an opening. Each sleeping area gets one outside: 2. No fuel appliance in a bedroom: 0. Total CO: 2.
- Interconnection.
More than one alarm of each type is required, so all of them must sound when any one does. Listed wireless alarms are accepted.
How the count changes with the plan
| Sleeping areas | Smoke | CO |
|---|---|---|
| 1 | 5 | 1 |
| 2 | 6 | 2 |
| 3 | 7 | 3 |
Same plan as the example (1 story, 4 bedrooms, gas furnace, attached shop) with more separate sleeping areas. Each extra sleeping area adds one smoke and one CO alarm.
What the model code requires
- Smoke, R314.3. Every sleeping room; outside each separate sleeping area near the bedrooms; each additional story including basements and habitable attics, not crawl spaces or uninhabitable attics.
- Split levels. With no door between levels and a lower level less than one full story down, an alarm on the upper level can serve the lower one.
- CO, R315.2.1 and R315.3. Needed with a fuel-fired appliance or an attached garage with an opening to the home. Outside each separate sleeping area; inside a bedroom that holds a fuel-burning appliance (or one in its attached bathroom).
- Combination alarms. Allowed in place of either type (R314.5, R315.4).
- Interconnection. Required for both when more than one alarm is needed (R314.4, R315.5).
Minimum counts, not placement. The code also sets placement limits this tool does not count: smoke alarms at least 3 ft from a bathroom door with a tub or shower, distance rules from cooking appliances, and extra alarms where a room has a much higher ceiling than the hallway. Many builders add alarms beyond the minimum, and all-electric homes often get CO alarms anyway. Which edition applies, and whether anyone inspects it, depends on your location. Tyler and other cities adopt their own codes; much of unincorporated Smith County does not enforce a residential building code (see the Smith County permits guide).
Where alarm counts go wrong
- Forgetting the shop. A shop with a door into the house triggers CO alarms even in an otherwise all-electric home.
- Counting one hall for two wings. A split plan has two sleeping areas, so two outside-the-bedroom alarms.
- Skipping the loft or basement. A habitable loft or basement is another story and needs its own smoke alarm.
- Mixing brands that do not link. Wired alarms from different makers often will not talk. Ask for a listed system, wired or wireless, that sounds every alarm.
What to ask your builder
- Where is each smoke and CO alarm on the plan? Ask for them drawn on the electrical plan.
- Wired and linked, or wireless? Wired alarms need a circuit and cable run before the walls close.
- Which code edition is the plan built to? Even where it is not enforced, many builders follow one.
- Do the shop and the house have separate alarms? See the shop planning guide.
Next step: get a written quote
This tool counts alarms, not the building or the price. We are a referral service, not a contractor; we connect visitors with independent local providers. Use the form below to ask independent barndominium builders near Tyler for a written quote that shows alarm locations and type on the electrical plan, and read how to choose a barndominium builder first.
Sources
- Chapter 3 Building Planning, 2021 IRC (UpCodes), R314 smoke alarms and R315 carbon monoxide alarms: locations, combination alarms and interconnection.
- 2021 International Residential Code, Chapter 3 (ICC), Original ICC publication of the same chapter.
Frequently asked questions
How many smoke alarms does a barndominium need?
The model code (IRC 2021 R314.3) asks for one alarm in each sleeping room, one outside each separate sleeping area near the bedrooms, and one on each additional story, including basements and habitable attics. A one-story, 3-bedroom home with one bedroom hall needs at least 4. More than one alarm must be interconnected so that one sounds all of them (R314.4).
Does a barndominium need carbon monoxide alarms?
Under the model code (R315.2.1), new homes need them if the home has a fuel-fired appliance or an attached garage with an opening into the living space. That covers gas or propane furnaces, water heaters, stoves and fireplaces, and a shop that connects to the house by a door. An all-electric home with no attached garage or shop does not trigger the rule, though a lender, insurer or builder may still ask for them.
Where do carbon monoxide alarms go?
Outside each separate sleeping area, in the immediate vicinity of the bedrooms (R315.3). If a fuel-burning appliance sits inside a bedroom or its attached bathroom, one more goes inside that bedroom. Unlike smoke alarms, the model code does not ask for one on every story.
Can I use combination smoke and CO alarms?
Yes. R314.5 and R315.4 allow combination units in place of either type. Since every CO location is also a smoke alarm location, combination units at those spots mean the smoke count is also your total device count.
Do the alarms have to be wired together?
Yes where more than one is required: one alarm sounding must sound all of them, for smoke (R314.4) and CO (R315.5). Listed wireless alarms satisfy this without running a wire between them. Smoke alarms also need building power with a battery backup (R314.6), except in buildings without commercial power.