Frontage Increase

[Nat]

I'm working on a renovation project (2015 Michigan Building Code) of a tenant suite (Mercantile) in a strip mall. Construction type is IIB, single story. The suite is around 13,500 SF. The City said it will need to be suppressed because the maximum SF is 12,500 per table 506.2. The building is surrounded by parking lot and open space, so I was hoping to use the frontage increase per 506.3.2 to increase the allowable area.

The City's response is that the frontage increase is "only for an increase in the square footage of a building as the same construction type. These calculation do not change the fact that the building still needs to be fire suppressed per MBC 2015 table 506.2, maximum square footage of 12,500 square feet." I'm not really sure what is meant by the first sentence in this response. I wasn't exactly sure if the frontage increase calculations can be used for a portion of a building or are meant only to apply to the entire building.

I was hoping to get some feedback on whether or not my initial thoughts about the frontage increase are valid before I push back on the City's response or ask for clarification.

Thanks!

 

[walker.t]

The suite is around 13,500 SF.

When you say “suite” is sounds like this “tenant suite” is part of a larger building. One way or the other, I wonder how they built the building with more than the allowable area per Table 506.2, maybe the building is divided by fire walls?

only for an increase in the square footage of a building as the same construction type

So you’re adding an addition to the building? If so, can you separate the addition with a fire wall? Sounds like you want to add an addition with a lower construction type, that would change the construction type of the building to the lowest construction type unless you separate the types of construction with a fire wall - a building is only allowed to have one construction type designation per 602.1.

'm working on a renovation project

If this involves a change of use, the building would need to meet the requirements of the code for the new occupancy group including allowable area and requirements for sprinklers.

 

[Sifu]

Using the IBC, not MBC but I think there may not be much daylight between the two codes. Your description doesn't provide enough information to understand what is going on. Frontage is the entire building, except if there are fire walls then you would do separate calculations for each building, but if there are fire walls you might not even need it since each one is evaluated a separate building. Assuming a mixed-use, non-separated strategy. You say the suite is 12,500, but not what the entire building is. However, in a mixed use building using the non-separated strategy you must use the most restrictive of all occupancies in the building from that table, so watch out for that if you have other classifications in the same building.

The allowable area line for a non-sprinklered building is just that....a non-sprinklered building. So when you increase the allowable area for a non-sprinklered building by using the frontage, it increases the allowable area for that same line in the table, which is still a non-sprinklered building.

Never heard anyone say the adjusted area can only be used to increase the size of the building but doesn't affect the allowable area for the non-sprinklered line in the table. If the building is larger than the allowable area with the frontage it would then need to move to the sprinklered line in the line in the table with the larger allowable area. If that is the case then they may be right, but their explanation is poor.

Or I have been doing it wrong.

 

[Nat]

When you say “suite” is sounds like this “tenant suite” is part of a larger building. One way or the other, I wonder how they built the building with more than the allowable area per Table 506.2, maybe the building is divided by fire walls?


So you’re adding an addition to the building? If so, can you separate the addition with a fire wall? Sounds like you want to add an addition with a lower construction type, that would change the construction type of the building to the lowest construction type unless you separate the types of construction with a fire wall - a building is only allowed to have one construction type designation per 602.1.


If this involves a change of use, the building would need to meet the requirements of the code for the new occupancy group including allowable area and requirements for sprinklers.

To clarify, we're not adding on the building or increasing the square footage. We are combining two tenant suites (strip mall) so the combined total is now over 12,500. There are CMU demising walls between the suites. I believe the previous occupant was also Mercantile, so not a use change. This is an interior renovation only. That's why the construction type comment is unclear to me.

 

[Nat]

Using the IBC, not MBC but I think there may not be much daylight between the two codes. Your description doesn't provide enough information to understand what is going on. Frontage is the entire building, except if there are fire walls then you would do separate calculations for each building, but if there are fire walls you might not even need it since each one is evaluated a separate building. Assuming a mixed-use, non-separated strategy. You say the suite is 12,500, but not what the entire building is. However, in a mixed use building using the non-separated strategy you must use the most restrictive of all occupancies in the building from that table, so watch out for that if you have other classifications in the same building.

The allowable area line for a non-sprinklered building is just that....a non-sprinklered building. So when you increase the allowable area for a non-sprinklered building by using the frontage, it increases the allowable area for that same line in the table, which is still a non-sprinklered building.

Never heard anyone say the adjusted area can only be used to increase the size of the building but doesn't affect the allowable area for the non-sprinklered line in the table. If the building is larger than the allowable area with the frontage it would then need to move to the sprinklered line in the line in the table with the larger allowable area. If that is the case then they may be right, but their explanation is poor.

Or I have been doing it wrong.

The entire strip mall is over 50,000 SF. It's my understanding that some suites are sprinklered, but about 1/3 - 1/2 the building is not.

 

[steveray]

Sprinklered? Total building size? Sounds weird...

 

[steveray]

I could see if it was broken into a bunch of fire areas and now you were combining 2 and >12,000 calling for sprinklers, but the 506.2 cite is weird unless they are fire walls....

903.2.7​

An automatic sprinkler system shall be provided throughout buildings containing a Group M occupancy where one of the following conditions exists:

1. 1.A Group M fire area exceeds 12,000 square feet (1115 m2).
2. 2.A Group M fire area is located more than three stories above grade plane.
3. 3.The combined area of all Group M fire areas on all floors, including any mezzanines, exceeds 24,000 square feet (2230 m2).
4. 4.Throughout stories below the level of exit discharge where such stories have an area exceeding 2,500 square feet (232 m2) and are used for the sale, storage or handling of combustible goods or merchandise.

 

[Nat]

Sprinklered? Total building size? Sounds weird...

I could see if it was broken into a bunch of fire areas and now you were combining 2 and >12,000 calling for sprinklers, but the 506.2 cite is weird unless they are fire walls....

903.2.7​

An automatic sprinkler system shall be provided throughout buildings containing a Group M occupancy where one of the following conditions exists:

1. 1.A Group M fire area exceeds 12,000 square feet (1115 m2).
2. 2.A Group M fire area is located more than three stories above grade plane.
3. 3.The combined area of all Group M fire areas on all floors, including any mezzanines, exceeds 24,000 square feet (2230 m2).
4. 4.Throughout stories below the level of exit discharge where such stories have an area exceeding 2,500 square feet (232 m2) and are used for the sale, storage or handling of combustible goods or merchandise.

Yeah, 903.2.7 seems more like what they should've been citing. This is helpful. If we have to comply, so be it, I just wanted a good reason why.

 

[walker.t]

There are CMU demising walls between the suites.

I’d confirm if the “demising walls” are fire walls meeting the definition in IBC Chapter 2. My guess is they are, otherwise I don’t know how they could have built such a large building with nonsprinklered Type IIB construction.

That's why the construction type comment is unclear to me.

Plans reviewers are only human and can make mistakes like anyone else. Maybe the drawings didn’t clearly communicate the scope of work. A polite phone call or email to ask for clarification would not be inappropriate in my opinion. [edited to correct typo "in appropriate"]

 

[Sifu]

Clearing up a little, and in the "plans examiners can make make mistakes" vein, I missed the over 12,000sf² thing. Sounds like they used fire walls to decrease the size of the building to build it, but the combined M would now require the sprinklers. The sprinklers would need to cover the entire building, which could be defined by fire walls if there are fire walls.

 

[Tim Mailloux]

I have a hard time imagining that this building has CMU fire walls dividing each tenant suite. Free standing / self supporting CMU fire walls and there foundations are very costly. I would tend think that providing a sprinkler system for the entire building would have been a more cost effective approach.

 

[Yankee Chronicler]

I'm working on a renovation project (2015 Michigan Building Code) of a tenant suite (Mercantile) in a strip mall. Construction type is IIB, single story. The suite is around 13,500 SF. The City said it will need to be suppressed because the maximum SF is 12,500 per table 506.2. The building is surrounded by parking lot and open space, so I was hoping to use the frontage increase per 506.3.2 to increase the allowable area.

The City's response is that the frontage increase is "only for an increase in the square footage of a building as the same construction type. These calculation do not change the fact that the building still needs to be fire suppressed per MBC 2015 table 506.2, maximum square footage of 12,500 square feet." I'm not really sure what is meant by the first sentence in this response. I wasn't exactly sure if the frontage increase calculations can be used for a portion of a building or are meant only to apply to the entire building.

I was hoping to get some feedback on whether or not my initial thoughts about the frontage increase are valid before I push back on the City's response or ask for clarification.

Thanks!

We need a lot more information:

• Where is it located -- Detroit, or elsewhere in Michigan?
• How old is the building?
• What code was it constructed under, and when?
• How many stories? One?
• How large is the building, and how large is the tenant space?
• What's the nature of the renovation?
• Why are you using the 2015 Michigan Building Code? UpCodes says Michigan has a 2021 MBC, based on the 2021 ICC Codes.
• If not in Detroit, Michigan has adopted the 2021 IEBC. Which compliance method are you following for IEBC compliance?