Okay, this is a common and critical question, and it hinges on a precise understanding of the applicable codes, particularly the IBC (International Building Code) and NFPA 72 (National Fire Alarm and Signaling Code). Since you mentioned "R-4 Residential" I'll assume that's what you're using, and NOT something like an "Apartment Hotel" classification.Here's a breakdown to help you determine the best approach

1. Determining if it's a Dwelling Unit or not:
Your Architect's Point

Your architect raises a valid concern. The presence of a shared kitchen and living room significantly strengthens the argument that the entire R-4 space constitutes a single "dwelling unit" for code purposes.

Code Definition

Refer to your adopted IBC code, Section 202 (Definitions). Look for the definition of "Dwelling Unit" or similar terms like "Family" or "Household". The key is whether the occupants share common living areas and cooking facilities.

Authority Having Jurisdiction (AHJ)



This is critical. The only definitive answer comes from your local building official (AHJ). Contact them before finalizing the design. Explain the situation clearly and get their interpretation of the code. Document their response in writing. Their interpretation always supersedes other interpretations. If it's a Dwelling Unit

If deemed a dwelling unit, the entire R-4 space needs to be treated as a single unit for fire alarm purposes, with interconnected smoke detectors.

2. Scenarios and Recommended Programming based on Dwelling Unit vs. NOT a Dwelling Unit



Scenario A: The R-4 Space is NOT a Dwelling Unit (e.g., a boarding house). This is very rare and usually requires an individual lease and not an overall lease. This would mean each sleeping room is its own sleeping unit. Sleeping Room Device Activation

Option 1: Alarm just the affected sleeping room (as you initially planned). This would require verification by the AHJ and a good argument. It is very common to have the other spaces in that area alarm. Option 2: Alarm the entire R-4 space.

This is the safer and generally recommended approach for non-dwelling-unit scenarios. It provides early warning to all occupants in the R-4 area. Either Option: Send a supervisory signal to the fire alarm control panel (FACP). Common Area Device Activation (Corridor/Kitchen/Living Room)

Alarm the entire R-4 space. This is crucial. Fire in a common area poses a risk to all sleeping rooms. Send a signal to the entire building. This may be necessary to fulfill code compliance. Send a signal to the FACP.

Scenario B: The R-4 Space IS a Dwelling Unit



Sleeping Room Device Activation



Alarm the ENTIRE R-4 space (all sleeping rooms, corridor, kitchen, and living room). Interconnected smoke detectors are required within the dwelling unit. Send a signal to the entire building. This may be necessary to fulfill code compliance. Send a signal to the FACP. Common Area Device Activation (Corridor/Kitchen/Living Room)

Alarm the ENTIRE R-4 space. Send a signal to the entire building. This may be necessary to fulfill code compliance. Send a signal to the FACP.

3. Alarming the Entire Building vs. Just the R-4 Area



Considerations



Code Requirements

The IBC and NFPA 72 dictate when the entire building must be alarmed. Look for sections on R-4 occupancies, fire alarm systems, and notification appliances.

Building Height and Size

Taller and larger buildings are more likely to require full building alarm on any initiation.

Occupancy Type

Other occupancies in the building (business, etc.) may influence the alarming requirements.

Fire Resistance

Is the R-4 area separated from the business area by fire-rated walls and doors? This can affect the need for full building alarm.

Voice Evacuation System

If the building has a voice evacuation system, you'll likely need to integrate the R-4 alarm into the system for clear instructions.

General Recommendation

Err on the side of caution. It's often best practice to alarm the entire building on any initiation within the R-4 area, especially if it's a dwelling unit. A fire in a residential space can quickly spread. It also becomes especially important if the R-4 is above the business in the building.

4. Supervisory vs. Alarm Signal



Sleeping Room Initiation (if NOT a dwelling unit)

Initially, sending a supervisory signal was OK only if you alarmed the sleeping room. The key is to alert occupants in the immediate area and notify the FACP for response. This will be extremely difficult to obtain as code typically required ALL spaces in the R-4 area to be alarmed.

Dwelling Unit or Common Area Initiation

Alarm signal to the entire R-4 and the FACP.

5. Specific Code References (Consult your adopted codes)



IBC

Section 907: Fire Alarm and Detection Systems (General Requirements) Section 907.2.9: Group R-4 (Specific Requirements) Section 202: Definitions (Dwelling Unit, Fire Area, etc.)

NFPA 72

Chapter 29: Single- and Multiple-Station Alarms and Household Fire Alarm Systems (for dwelling units) Chapter 17: Initiating Device Circuits Chapter 18: Notification Appliance Circuits

Action Steps


Contact the AHJ IMMEDIATELY. Document their decision.2. Review your local codes THOROUGHLY.3. Consult with a qualified fire alarm engineer. They can perform a code analysis and design a system that meets all requirements.4. Update your fire alarm system design documents based on the AHJ's interpretation and the code requirements.5. Clearly document the alarm programming in the system documentation.Key Takeaways: The "dwelling unit" determination is paramount. The AHJ's interpretation is the final word. Prioritize life safety. Err on the side of a more comprehensive alarm response.* Document everything.By following these steps, you'll be able to design a fire alarm system that is code-compliant and provides the highest level of safety for the building occupants. Good luck! Flag for review