Options for Exit/Stair Widths without EVACS?

11/3/2022

We have a building that was designed with exit width and stair width per occupant using the exception CBC 1005.3.1 for a sprinklered building with EVACS (emergency voice/alarm communication system), however, the fire alarm design drawings show horns/strobes.

Found out through the fire alarm deferred submittal corrections.

Changing the width of stairs and exit doors is not an option as the shell is already built.

The EVACS option will cause delays, cost impacts, and material procurement challenges and not advised by FD because building has inherent ambient noise associated with building operations.

What options do we have?

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2 Comments

Alex

11/3/2022 08:18:07 am

Hi,

I'm guessing you have already recalculated your occupant load with horn/strobes, correct? If you are over your allowed occupant load:
- I never work in Canada but would the AHJ allow for posted occupant loads?
- Exterior exit stair (costly)
- Horizontal exit?

Thanks,
Alex

Todd E Wyatt

11/3/2022 09:04:40 am

Does the reference to “CBC 1005.3.1” references the “California Building Code 1005.3.1” and not the National Building Code of Canada?

Assuming it does, Exception 1 permits the MOE capacity factor to be reduced from 0.3 inch/occupant to 0.2 inch/occupant IF the building is protected by an automatic sprinkler system (ASPS) OR if it includes an emergency voice/alarm communication system (EVACS). I am assuming the building does not have an ASPS so this is why the EVACS was selected.

The previous recommendations of limiting the Occupant Load (OL) with signage on the stories above the Level of Discharge is worth checking with the AHJ. The Horizontal Exit (HE) recommendation will only permit the OL to be “temporarily” relocated to an adjacent Fire Area which would still require an Interior Exit Stairway (IES) sized using 0.2 vs 0.3 so this will not affect that issue.

It has been my experience that Design Professionals incorrectly attribute the Occupancy Classification (OC) such as Business, Storage, or Assembly to determine the OL instead of correctly attributing the actual “Function of Space” per CBC Table 1004.5 Maximum Floor Area Allowances Per Occupant to each room, area, or space to calculate the OL. I recommend you request the Design Professional to redetermine the OL using this process vs the OC “estimation”.

Lastly, the requirements of the EVACS per 907.5.2.2 includes prescriptive requirements to address situations like this, including visible alarms so even though the FD does not “recommend” their inclusion, if the system meets the Code requirements, the AHJ should permit it.

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Options for Exit/Stair Widths without EVACS?

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