Part 3 Bldg Classification & Construction, Superimposed Major Occupancies

[Steve French]

Hey Folks,

Curious to hear from others about their interpretation of 3.2.2.6. and 3.2.2.7 of the 2020 NBC, specifically how they relate to one another when considering building classification - here's a scenario:

• 4-storey building consisting of 50% A2 and 50% F3 on the ground floor with three full floors of apartments above.
• A2 is not subsidiary to the C occupancy.

3.2.2.6. would have a person think that the building should be constructed entirely as per 3.2.2.24. if it weren't for "Except as permitted by Articles 3.2.2.7...", which could lead to Sentence 1) of 3.2.2.7. being interpreted as a building would not have to be wholly constructed as per the most restrictive major occupancy in the building *if* major occupancies are superimposed and each major occupancy is constructed as per its own 3.2.2. classification as though the entire building were of that classification - e.g. the ground floor would be constructed in accordance with the requirements of 3.2.2.24. and the upper storeys of the building as per 3.2.2.52.

Thoughts?

 

[Wstubbs]

hey i like the name and profile pic. lol.. coming outta sunnyvale?

 

[Steve French]

hey i like the name and profile pic. lol.. coming outta sunnyvale?

Happy to see another fan!

 

[steveray]

Hey Folks,

Curious to hear from others about their interpretation of 3.2.2.6. and 3.2.2.7 of the 2020 NBC, specifically how they relate to one another when considering building classification - here's a scenario:

• 4-storey building consisting of 50% A2 and 50% F3 on the ground floor with three full floors of apartments above.
• A2 is not subsidiary to the C occupancy.

3.2.2.6. would have a person think that the building should be constructed entirely as per 3.2.2.24. if it weren't for "Except as permitted by Articles 3.2.2.7...", which could lead to Sentence 1) of 3.2.2.7. being interpreted as a building would not have to be wholly constructed as per the most restrictive major occupancy in the building *if* major occupancies are superimposed and each major occupancy is constructed as per its own 3.2.2. classification as though the entire building were of that classification - e.g. the ground floor would be constructed in accordance with the requirements of 3.2.2.24. and the upper storeys of the building as per 3.2.2.52.

Thoughts?

Welcome to THE forum....Some of our expert neighbors to the North will be along shortly I am sure..

 

[tmurray]

When read as a composite, the function of both 3.2.2.6. and 3.2.2.7. is such that if we have lesser requirements on higher stories than stories below, the more restrictive fire rating requirements on stories below do not apply to the upper stories.

For example, if we needed 1 hour ratings for the A2 and/or the F3, but only needed 45 minutes for the C, the storeys with the C occupancy would only need to be supported by 45 minutes. However, the building needs classified in accordance with the most restrictive 3.2.2. classification to determine if it needs sprinklers, etc.

 

[Ask Bing Code]

Hey Folks,

Curious to hear from others about their interpretation of 3.2.2.6. and 3.2.2.7 of the 2020 NBC, specifically how they relate to one another when considering building classification - here's a scenario:

• 4-storey building consisting of 50% A2 and 50% F3 on the ground floor with three full floors of apartments above.
• A2 is not subsidiary to the C occupancy.

3.2.2.6. would have a person think that the building should be constructed entirely as per 3.2.2.24. if it weren't for "Except as permitted by Articles 3.2.2.7...", which could lead to Sentence 1) of 3.2.2.7. being interpreted as a building would not have to be wholly constructed as per the most restrictive major occupancy in the building *if* major occupancies are superimposed and each major occupancy is constructed as per its own 3.2.2. classification as though the entire building were of that classification - e.g. the ground floor would be constructed in accordance with the requirements of 3.2.2.24. and the upper storeys of the building as per 3.2.2.52.

Thoughts?

You are 100% right!

 

[Steve French]

When read as a composite, the function of both 3.2.2.6. and 3.2.2.7. is such that if we have lesser requirements on higher stories than stories below, the more restrictive fire rating requirements on stories below do not apply to the upper stories.

For example, if we needed 1 hour ratings for the A2 and/or the F3, but only needed 45 minutes for the C, the storeys with the C occupancy would only need to be supported by 45 minutes. However, the building needs classified in accordance with the most restrictive 3.2.2. classification to determine if it needs sprinklers, etc.

Thanks Murray, this is how I've always read it but a recent conversation had me doubting my approach as it isn't explicitly stated anywhere that I can find, only inferred and somewhat supported by other sentences. Have you found any resources that clearly explain the intent?

You are 100% right!

Always nice to hear, not that I often do lol!

 

[tmurray]

The 1995 user guide goes into this in a little more depth: https://nrc-publications.canada.ca/eng/view/ft/?id=f4c59aa5-16df-4b40-b9db-d6c65cae71de

While it is from 1995, the basic code intent remains the same today.

 

[Steve French]

The 1995 user guide goes into this in a little more depth: https://nrc-publications.canada.ca/eng/view/ft/?id=f4c59aa5-16df-4b40-b9db-d6c65cae71de

While it is from 1995, the basic code intent remains the same today.

"If a multi-storey building has more than one principal function, each storey must be classified for its major occupancy. For example, the entry storey could be used primarily for mercantile operations and upper storeys could contain offices. In this case, the building as a whole would be classified for both types of occupancy and would be considered to have two major occupancies; business and personal services (Group D) and mercantile (Group E). Each major occupancy could include subsidiary occupancies."

Most relevant section I could find on Page 6, which I think would have been perfect if expanded by just a few more lines...