R2 Building height & type of construction

[Scott555]

In IBC 2006 and/or 2009, can I build a 4 story, wood-framed structure in Residential R2 group for apartments? Building will be sprinklered. Ground floor to have individual private garages and some apartments with 3 stories of apartments above. Also, what are my height limitations?

Thank you.

[Jerry Peck - Codeman]

What Type of construction are your considering, and protected or unprotected (i.e., Type VA or Type VB)?

Type VA (protected) might be at first glance as, for R-2 occupancy, that would be allowed to have a height of 3 stories and 12,000 square feet, if the sprinkler system met NFPA 13 or possibly NFPA 13R (the garages make this structure a mixed-use occupancy which could affect that choice) the the number of stories may be increased by one (from 3 stories to 4 stories) with some limitations.

You may want to consider a masonry first floor with wood frame above that?

What area of the country are you and what does the local AHJ say?

Only scratching the surface here as there is not a lot of information to go on.

[Scott555]

Thanks.
All wood frame VA protected. Garages are private, individually separated with fire partitions between each space (just like a garage to a house). Builder wants to stay all frame no masonry. Yes on sprinklers. Chicago suburbs, will be built in several municipalities - each village has own code but most follow either 2006 or 2009 IBC.

[Jerry Peck - Codeman]

I know someone who is, I believe, experienced in the Chicago codes.

I'll contact them to find out for sure, if so, they may have a better answer than I do as Illinois, and especially Chicago, have more restrictive codes than many other places, such as not allowing NM cable and other things.

[Scott555]

Ok, although this isn't inside the City of Chicago, surrounding suburbs. As I mentioned - using 2006 and 2009 IBC is all I am looking for, thanks...

[Jerry Peck - Codeman]

Scott,

From the information given so far, the 2006 IBC would allow Type VA (protected) at 3 stories with a 1 story increase for being fully sprinklered as specified in the code, which puts the number of stores at 4 stories for that structure.

I now another question based on your description of the garages. While I do not see where this would affect the allowable height limitation, it would allow different fire-resistance rating between floors and horizontally between units. Will each unit have a private garage, will each private garage be all or part of the first floor of each unit, and will each unit be 4 stories (similar to attached townhouses), or would the garage be private for one tenants use but not be part of their unit, such as the garage may be rented by the various tenants as the garages are available but not all tenants would have a garage available (similar to an apartment building with a common garage area except that each garage is a separate garage from the other garages)?

An example would be that the latter would require greater and more restrictive fire-resistance rating between floors than if each unit was vertically constructed.

The short answer to your question, though, is that given the conditions discussed above my reading is that you would be allowed to construct the structures as wood frame structures for a height a 4 stories.

The reason I mentioned, and have contacted, the other person is that it is my understanding that when the 2006 or 2009 I-Codes are in use in Illinois, Illinois has many amendments and revisions specific to Illinois.

[Scott555]

Thanks Jerry,
The latter description is correct. They are private garages that do not enter directly into a unit and may be rented individually. The apt. units are stacked flat apartments (1 floor only). The garages are separated with fire partitions from each other and the corridor they serve. The way the local interpreted the garages were classified as S-2 and units are R-2 and structure built as type VA protected w/sprinklers. The horiz. floor/clg. assembly above would be separated with 1-hour assembly (with sprinklers). That is how the local interpreted it at 3-stories, now we are considering the same concept in 4-stories.

[Jerry Peck - Codeman]

Scott,

Why were the 3 story building proposed with the fire sprinkler system?

I ask because if the fire sprinkler system was used to reduce the fire-resistance rating requirements, then the fire sprinkler system cannot also be used for the 1 story increase in height.

If the fire sprinkler were in the 3 story building "just because" the designer wanted them, then I don't see a prohibition to using the fire sprinkler system for the additional 1 story increase in height.

[Scott555]

Sprinklers were required in the R2 use group as there is no direct egress to grade from individual units, this is a corridor building (not specifically to reduce ratings). 22 units in the building.

[markus]

I think Jerry has answered the Code portions of this question pretty well. I don't study the IRC enough to state better without doing some research. Right now I have too many reports to write do the research. I will point out a couple things though. Also these are the types of questions I would pawn off on my architect.
- This does not sound like a good idea. 4 story, 4B construction for a corridor building. I have to wonder about the logic of this scenario. For higher end rental it isn't going to work without an elevator. For lower end subsidized housing no elevator and zoning approval could also be an issue. For middle of the road rental it might work but it would really depend on aesthetics.
- You mention doing this in multiple suburbs, a cookie cutter thing. I would be very careful about your design on that. Some of the suburbs get really picky about NIMBY.
- I deal with subsidized housing issues from time to time. I can't say whether it would be denied or approved since it hasn't come up. Knowing some of the requirements and issues I would doubt it would get a green light for government money.
- Travel distance on the corridors shouldn't be an issue with only 22 units, whether sprinklered or not
- As much as I really hate CMU, I have to go along with Jerry's idea of at least doing the 1st floor in masonry. This would help with garage fire separation and approval. Doing the stairwells in CMU would also be a better idea. Have you considered structural metal studs for the exterior wall framing? Not too popular around here but it is done. There's a building in Evanston on Asbury just north of Howard, west side of the street, blue and white 4 story, can't remember for sure, all structural metal studs.