# Construction type for masonry exterior building



## piscescon (Mar 23, 2021)

What is the construction type for a building with masonry exterior walls, wood studs interior walls and wood roof trusses?

I saw both architects and engineers have used type V-B on some drawings. But I think it should be III-B. I’m in Florida. Which one is correct?


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## EBAT75 (Mar 24, 2021)

Wouldn’t fire separation distance have a bearing on the Type? Unless you are comparing that between the drawings you are referring to, it would be Washington apples vs Florida oranges. I love them both!

Please look at Table 602 also. Another thought is local jurisdiction. Local building standards adopt IBC with their own modifications. Maybe why.


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## piscescon (Mar 24, 2021)

I’ve checked local codes. Nothing is different from IBC. Those architects and engineers are lazy people and going to retire soon. They don’t want to take any risks so just put everything on the most conservative side.


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## EBAT75 (Mar 24, 2021)

In that case, take it up with the local building official. I suppose if you are “going over the heads”, and it causes friction at your workplace, it can be tricky. Good luck. 

I will be a bystander, just watching.


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## leggo PE (Mar 24, 2021)

I think it depends on square footage and potentially story number for fire rating reasons. So, depending on said square footage alone, it could be either. Typically, fire walls will be introduced in a larger footprint to reduce from Type III to Type V.


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## piscescon (Mar 26, 2021)

I’ve seen another good architect in another firm specified III-B for a similar project.


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## EBAT75 (Mar 26, 2021)

“They don’t want to take any risks so just put everything on the most conservative side.”

It has been 20 years since I worked on some health care facilities, so I am a bit rusty on Construction Types. But is going to 5 conservative? I say this because V can use any material. Is that okay from a safety point of view? I thought III is more “ conservative “, more costly; the reverse with V. Maybe their clients are pinching their dollars, why the others are going with V.

My understanding is this. The variables are - Fire rating, Fire separation distance, Occupancy Group, and Building Elements.

Unless your comparison is based on the overall congruence of these variables between the two buildings, they may not be comparable to each other. Not to say they have to be identical, but at the end of navigating all the variables are you arriving at a comparable situation?

It is not clear whether you have all their project data.


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## piscescon (Mar 26, 2021)

If you look at III-B, it can use any materials, except exterior walls must be brick or masonry.


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## EBAT75 (Mar 26, 2021)

I knew that was the case, but are you also impacted by the footnotes e and f in Table 601? Sec 704.10?

By setbacks, do you mean fire separation distance, or is it foundations set backs from slopes or is it footprint setback from property line? Hard to imagine they would be the same for all projects.


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## piscescon (Mar 26, 2021)

Setback is the distance from exterior wall to lot boundary or easement. Different zones have different setbacks no matter what construction type it is.


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## EBAT75 (Mar 26, 2021)

Fire separation distance is more than that. It can be exterior wall to street centerline, it can also be perpendicular distance between exterior walls of two separate buildings on the same lot.

I also


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## EBAT75 (Mar 26, 2021)

Sorry accidentally pushed before I finished it.

I also thought it must be the distance to lot line your comparison is about but can the distance to street/alley centerline or any other building on the same lot be making a difference?

As these are variables that define the Type based on Tables 601, 602, 704.10 *AND the definition of Fire Separation Distance*, it is not possible to typify unless you compare ALL these variables between two projects you are comparing.


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## piscescon (Mar 27, 2021)

I’m comparing a retail store and a restaurant. Our engineer specified the retail store as construction type V-B but another architect in another firm specified the restaurant as type III-B.
Both have 8 inch masonry exterior walls and wood roof trusses. The retail store is to be built in a higher density commercial zone. However, both rear setbacks are 10 feet and both front setbacks are 25 feet. Only difference is the building height/story permitted. Setbacks are measured from building exterior walls to lot boundaries/easements, which are smaller. Lot boundaries are typical 25 feet offset from center line of road, if Right-of-way is 50 feet wide. Easements are the space occupied or preoccupied by the utility lines inside of lots. Fire separation distance is 20 feet between adjacent buildings, which is the same as suburban residential zone. Fire separation distance is 100 feet if they are facing each other on a street. Side setback is 20 feet if it’s a corner lot. Construction types should be very easy to define through building codes because there are just a few sentences about them.


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## piscescon (Mar 27, 2021)

Retail store is in occupancy group M and restaurant is in group A. They don’t have any differences in table 602. Please note that 8 inch masonry exterior walls are 2 hours fire resistance rating so table 602 is even inapplicable at all. Normally a commercial 8 inch masonry wall was designed with stucco exterior finishing (0.5-1 hour) and 1/2 thick drywall interior finishing (0.5 hour), it’s even good enough for the most dangerous group H.


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## EBAT75 (Mar 27, 2021)

Thank you for the details. Makes it easier now.

It is not that Table 602 does not apply. Just that it is being met from the setback and separation distances mentioned in relation to the fire rating.

I don’t know if there is some interior detail that has an impact, one being a restaurant the other being retail. For instance, provision of sprinklers or not; firewalls (restaurant kitchen - higher interior fire risk); using fire retardant treated wood vs pressure treated etc.

You are closest to the project. You have all the details. If you are satisfied, the curiosity question I have goes back to what I said earlier.

Isn’t Type III-B more costly than Type V-B construction? Why is it then described as more conservative? From what viewpoint?

Maybe present your plans to the building official and see where it goes.


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## piscescon (Mar 27, 2021)

Theoretically, when design a same building, Type V-B needs more fire resistance than III-B, such as thicker drywalls, larger fire separation distance, so I think it’s on conservative side. In fact, it’s not always true. V-B looks cheaper because any materials can be used. However, III-B is the same. Any materials can be used in III-B except exterior wall. In south Florida, exterior masonry walls are very popular because of the wind loads, flooding and humidity. It’s owner’s call to use masonry blocks. Most owners refuse to use wood frames. However, there are still some 100% wood frame houses built every year. Two story houses normally have wood frames at second level. I’ve never seen a one story commercial building was built recently with wood frame exterior walls. Some architects/engineers don’t want to change the construction type on their typical drawings (general notes/cover sheet) for all type of projects. I’ve seen a steel frame building marked with V-B as well. This is why I say they are lazy.


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## EBAT75 (Mar 27, 2021)

At the end of the day, it’s about cost. When I was working for a Big Four consulting engineering firm in Canada (one of the biggest globally now), when they were discussing an issue, I overheard an old timer tell another engineer who asked “So, what’s the problem?”. Pat came the answer. “It’s NO problem. Just cost.”.

Going beyond code minimum such as masonry walls when not needed can be an owner’s requirement at their cost. I was thinking in general V-B to be less costly for the same square footage and meeting the code minimum.

Finally, there may be more than meets the eye when it comes to what you describe as laziness. It may also be the economy of production that drives the engineering business since the qualification based selection died. Repetitive design is one way to quote lower bids. Very customized design and detailing may not be winning contracts.

Anyway thanks for piquing my interest. Good luck.


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## piscescon (Mar 27, 2021)

Actually I’m the new owner of the business. I just want to improve the quality of our productions. I may create drawing templates for each type of buildings. Also, I have been working in Canadian big-four as well and I’m Canadian. Thanks for your help. Much appreciated.


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## EBAT75 (Mar 27, 2021)

Canadian, Eh! Hope they have Molson Canadian cases on the shelves in Southern Florida. Stay in touch.


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## Emidem (Nov 12, 2021)

When my wife and I were renovating our house, we decided to go straight to the builders and designers to avoid spoiling anything. We even talked to them about what would be in our back and front yards. We also arranged through the online site to have a good gutter installed because the old one was rusty and completely clogged. I heard that they make gutters with mesh now and thought it was an excellent opportunity to save some extra work. Especially since we already have a lot of time to spend on repairs, buying materials, and no one canceled work.


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