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Architecture/Fire rated corridor


QUESTION: I am working on a project in Florida designing a medical office, the florida building code says you need a fire rated corridor when the occupant load served by the corridor is more than 30 people, What does that mean? If the occupant load is 40 persons, if this the occupant load served by the corridor?


ANSWER: The 2010 Florida Building Code is patterned after the 2009 International Building Code.

The type of occupancy for a medical office (outpatient) would be Business "B".

Table 1004.1.1 of the Florida Building Code dictates that an occupant load of 1 person for every 100 square feet (gross) of building area would calculate to be 40 occupants for a building that consists of 4,000 S.F. medical office.  The corridor and corridor doors and any stairways within that building would then need to accommodate an occupant load of 40 people.  

Table 715.4 of the Florida Building Code dictates that the walls (and ceiling) of the corridor be constructed as a one-hour fire-rated partition.  Doors within the corridor walls need to be 20 minute fire-rated doors with automatic closers.  These doors are typically solid wood doors with spring hinges.  The doors need to have lever handles that latch when closed.

There are two exceptions to this basic rule:

1) If the building is equipped with an automatic fire sprinkler system, then the corridor does not need to be fire-rated.

2) If the occupant load being served by the corridor is less than 30 occupants (essentially a 2,999 S.F. office/medical building - or smaller), then the corridor walls do not need to be fire-rated.

There are different ways to calculate the occupant load.  You could take the overall square feet of the building divided by an occupant load factor of 100.  Or you could take the square feet area of each room divided by the occupant load for that particular room (see again Table 1004.1.1.) and then round up to the nearest whole number.  For example, every exam room measuring 150 square feet would be assigned an occupant load of 2 people.  All rooms would be added together for the entire building to achieve the total number.  Restrooms, mechanical equipment rooms and corridors would be considered accessory spaces and assigned an occupant load of zero.  Storage rooms would have an occupant load of one person for every 300 square feet.

Although this is elementary math, you should show your work for the sake of discussion.  It also makes the job of the building official much easier while reviewing your design.

I hope all of that makes sense.  Send me a floor plan when you get a chance.

Richard Burton, AIA
Registered Architect (but not licensed in Florida)
ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner

---------- FOLLOW-UP ----------

QUESTION: Does the corridor capacity changes if I have 2  or more exits? The building does not have sprinklers but it has fire alarm system.

Good question.  It took me six years to figure out the answer for myself.
No, the corridor capacity (40) remains the same throughout the building.
Therefore, the corridors need to be fire rated even if you could otherwise argue that four short corridors leading to four exits would each have an occupant load of only 10 each.  (40 / 4 = 10).

Richard Burton, AIA
Registered Architect (but not licensed in Florida)
ICC Certified Plan Reviewer
NFPA Certified Fire Plan Examiner


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Richard Burton AIA


A combined total of 25 years experience with construction, architecture, and building code enforcement. Ask me about residential and commercial design. Ask me about design aesthetics, structural methods, and building something that will withstand severe weather conditions. Ask me my opinion about YOUR design ideas and I will tell you the merits of good design and challenge your thinking about practical issues. Ask me how to best find and work with your local architect and approach general contractors to get the most value for the least amount of headaches. You can ask me about improving your energy efficiency and things that are both green and practical. But don't ask me about solar panels and wind turbines unless you are currently paying your utility company 35 cents per Kilowatt. Otherwise the math does not justify the initial cost and return on investment. Ask me any building code question and how to get a building permit from the most difficult enforcement agencies.


Here in the midwest, we design and build "green" in ways that make sense. My construction methods prioritize weather resistance, ease of maintenance and durability. While a graduate student in San Diego, I taught drafting and history of architecture. After working ten years for other architecture firms, I have started my firm Arrow Architecture in 2008. More than half of my work involves commercial office buildings. But my portfolio of work also includes custom homes, residential additions, home remodels, and second story additions.

President-Elect of American Institute of Architects - Lincoln, NE

B.S. Architecture - (Interior Design) University of Nebraska Lincoln 1997 Master of Architecture - (Urban Design and Professional Practice) NewSchool of Architecture - San Diego 2004 Graduated Summa Cum Laude ICC Certified Building Plans Examiner

Awards and Honors
AIA Henry Adams Medal and Certificate

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