Three Levels of Residential Over Ground Floor Retail

[fj80]

2015 IBC

If we want to build three stories of apartment units (R-2) with wood framing over one story of ground floor retail spaces (M), do the apartments and retail space have to be separated by a 3-hour fire-rated floor between the two uses?

And, does the first level have to be built out of concrete? Or could the first level also be framed with wood?

 

[RLGA]

Q1: No, as long as the construction is Type VA, which allows a four-story Group R-2 building.
Q2/3: The first level can be framed with wood.

Now, if you do not want the wood framing to be Type VA, then you are limited to three stories for the Group R-2 as a Type VB building, which means then you will need to use the horizontal separation allowance per Section 510.2. That would require Type IA construction on the first story and Type VB construction on the upper three stories separated by a 3-hour horizontal assembly.

 

[RLGA]

Just to clarify further, with Type VB construction you will still need to separate the dwelling units from each other and from the Group M with 1-hour or 30-minute fire partitions and horizontal assemblies, depending on which type of sprinkler system is installed.

 

[fj80]

Just to clarify further, with Type VB construction you will still need to separate the dwelling units from each other and from the Group M with 1-hour or 30-minute fire partitions and horizontal assemblies, depending on which type of sprinkler system is installed.

Thanks. One correction, I think: per IBC Table 508.4 it appears the fire rating between the retail level and apartments above would be either 1-hour or 2-hour, correct?

 

[RLGA]

Thanks. One correction, I think: per IBC Table 508.4 it appears the fire rating between the retail level and apartments above would be either 1-hour or 2-hour, correct?

Only if you are using the separated occupancies method per Section 508.4. If using the nonseparated occupancies method per Section 508.3, then Table 508.4 does not apply.

 

[Yikes]

fj80 - -my unsolicited opinion, based on my own experience and as RGLA indicated - - even if you go for Type V-B, there are so many one hour walls anyway that you might as well do type V-A and just be done with it.

 

[fj80]

Our structural engineer convinced us to build the first floor as a podium out of concrete columns and slab with steel framing for non-bearing walls because we'll get much larger clear spans for the retail space than we would with wood. So in that scenario would it make sense to consider the first floor podium as type I-A construction, and stay with V-A wood framing for the three levels above?

 

[RLGA]

You can do that, but if the allowable area works, I’d still classify the entire building as Type VA and not have to worry about complying with Type IA construction on the first story. Type V construction allows any construction materials permitted by the code, so a part of the building can be concrete, masonry, and/or steel and still be considered Type V construction.