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Where is 'missing middle' allowed to be built under IRC?

S

Shams Gannon

Registered User
Joined
Sep 9, 2019
Messages
28
Location
Austin Texas
Hi code friends, I'm trying to compile a list of jurisdictions that have updated their IRC to allow small multifamily. Memphis and Shelby County allow up to six units codified as a 'Large House', and I know North Carolina is attempting that move as well (although, maybe defeated by the home builders who lobbied against an energy code update??).

Do any of you know any other jurisdictions that have allowed smaller multifamily under IRC?

What is y'alls opinion on this reform?
 
I am not sure what you are asking and why.
If you are building townhomes under the IRC, there is no limit as to how many units there can be.

[RB] TOWNHOUSE. A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from foundation to roof and with a yard or public way on not less than two sides.
 
Some jurisdictions are moving the limit of units from two to four or six for what can be built under the IRC. Memphis has updated it's code to allow 6-plexes and NC was set to do the same last month. Seattle's Housing Task Force has also requested the city adapt this change, and provides a list of reasons.

Austin is currently looking at allowing four units by right for any residentially zoned lot, however, the residential builders are squeamish of building under the IBC. Our early modeling, in tandem with local builders, is showing that even though four units may be allowed, most local builders would prefer to build a single duplex to avoid triggering the IRC. Moving four unit buildings into the IRC would align with our zoning reform as well as still fall under the FHA loans these builders are used to.
 
Townhouses are built under the standard IRC code, we have a contractor building a seven unit townhome meeting the unamended IRC right now. The IRC has allowed this for as long as I can remember.

Are you talking about zoning regulations, rather than building code?

If you are talking about multifamily that is not townhouses, I would not support building them out of the IRC - the IBC rules are there for many fire, structural, and life safety reasons and do not need to be relaxed to IRC levels. Frankly, I think the IRC should be limited to just one-and two family housing, and not include townhouses.
 
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No, I'm not talking about zoning regulations, and I'm not talking about townhomes. I'm looking for precedent jurisdictions that allow small multifamily, like a stacked three or fourplex to be built under the IRC. Memphis amended their code to allow up to six units to be built under IRC as opposed to IBC. NC just passed state wide legislation allowing for 4 unit residential projects to be built under IRC.

Also, I'm in that texas monthly article. That's me. Chris Gannon.
 
They could, however, we have found that residential builders are squeamish about crossing from IRC to IBC. They fear it will result in more expensive construction costs. In order to remove that barrier to entry, and help facilitate more neighborhood infill projects, some jurisdictions are looking at bringing small scale multifamily (four to six units) under the IRC.

Seattle's Housing Task Force provides an excellent explanation for wanting this building code revision.
 
I am unaware of any jurisdictions in the state of Kansas who are planning to allow small multifamily that are not townhouses under the IRC. I estimate that I am 85% likely to know if they were.

There is a disturbing trend of relaxing and removing building codes by people (politicians) who have no idea why those rules were implemented in the first place, like NC removing the fairly important sheathing inspection because they were (justifiably) mad at the energy codes.

I really can't blame developers and contractors for wanting to build bigger buildings with more lax codes on the same piece of land, but it creates major safety implications long-term. Moving out of the IBC does make construction cheaper - by removing sprinkler requirements, size and construction type requirements, plenum requirements, fire safing requirements, egress requirements, and a whole host of other important items from the IPC and IMC codes. The IBC and the IRC are radically different books, and they really don't apply in each other's realms.

Back when I was on the contractor side of the desk, I would probably have supported this. Now that I understand the codes involved and what they are trying to achieve, there is no way.
 
Thank you @Beniah Naylor ! This is what I'm looking for.

I believe the counter argument would be that a fourplex is far more similar to a single family house than a 100+ apartment building, although they could fall under the same occupancy and building type under IBC.

In your opinion what would you adjust in the IRC to make it more applicable for homes with up to four units? I'm thinking of a Boston triple decker or a small, prewar six-plex apartment. I understand the IRC is a complex document and there's no simple answer here, but I'm wondering if there's any certain requirements that would make it better suited?
 
I agree with Beniah, on the surface it sounds reasonable, but a deeper analysis will show lots of potential problems IMHO. I believe the townhouse design covers this quite well. You want six units in one building? No problem, build them like townhomes. In California I really don't think this would make much difference at all cost wise, we require sprinklers in new single family houses, and large portions of the state are in high seismic zones which can trigger engineering for certain designs.
 
The main issues I have relate to height and area, proper fire seperation, sprinklers, and egress. This is not an exhaustive list, this is just what I came up with off the top of my head.

Egress directly from each unit to grade would be important, you don't want to be sharing a hallway in the middle to get out because there is no corridor protection requirements in the IRC.

The IRC does not contain specific provisions for fire walls as we know them in the commercial world.

You have more people living in a single building. Given that the top 3 causes of fire are men, women, and children, you increase the likelihood of a fire event in general.

In the IBC, you can build an R2 like Rick said a maximum of 2 stories and 7,000 square feet total out of wood before you would need sprinklers. The IRC allows three stories, has no square footage maximum, and several states have laws that prohibit the requiring of sprinklers in IRC buildings, so theoretically you could build a giant 4 plex or 6 plex on each lot of a block, 5' from the lot lines so that they are only 10' apart. If one catches on fire, you could lose the whole block.

The IRC actually allows the buildings to touch each other if they are separated by a 1 hour wall.

What kind of fire separation between units would you have? The IRC has no guidance that would apply there, would you use the requirements for duplex separation, or townhouse separation?

IRC does not limit materials in plenums except for NM cable and foam plastic, whereas the I-codes for commercial construction have many materials not allowed in plenums because the burn with toxic smoke that is then distributed throughout the house by the mechanical system.

Fire alarms (not smoke alarms) - not required in the IRC, definitely required in the IBC for R2 per 907.2.9
 
The only dilemma with townhomes is the required street frontage. In Austin our minimum lot width is 50’, which is what most lots are. Lose 10’ to side yard setbacks, and you’re left with 40’, which gives two 20’ wide town homes. If you want to park a car it’s even less (~16’ each).

Allowing for stacked flats would provide for more units and better utilize the street frontage. Again, think of a Boston triple decker.
 
The cost in multifamily is not exclusively building code requirements. Four units and you will have to comply with Fair Housing construction requirements within the dwelling units along with the accessibility requirements in the building code as referenced in the IRC. How many parking spaces are required per dwelling unit and do they have to be onsite. Any impact fees? you will have to provide a larger water service for 4 dwelling units. Are the existing infrastructure sized to accommodate the additional water and sewer impacts. How about fire flows in the subdivision area to fight a fire. And on and on we can go.
 
Shams Gannon said:
The only dilemma with townhomes is the required street frontage.
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Where does this come from? Apologies for my ignorance on IRC, California has lots of amendments/deletions so I may not have the same language you're looking at. My code defines:

[RB] TOWNHOUSE. A building that contains three or more attached townhouse units.
[RB] TOWNHOUSE UNIT. A single-family dwelling unit in a townhouse that extends from foundation to roof and that has a yard or public way on not less than two sides.
 
@mtlogcabin these are great points as well. Switching from IBC to IRC will definitely not solve all the development woes associated with building at this density, but it may help allow smaller residential builders to get into the missing middle game.

For background, Austin’s city council is working to update our city code to encourage more incremental density in our central neighborhoods. Our current code is from the 1980s and is highly exclusionary. This is an involved process of code coordination across multiple regulatory bodies, chasing down the many threads that prevent this desired level of density. We’ve already updated our site plan process and zoning to allow for four units, and removed parking minimums city wide. There’s a lot of smaller details as well, like allowing more than four in related people in one building, and relaxing rental constraints. Moving four plexus into the IRC is just one facet of this process, and one that will take a lot of research to get right. I’m trying to see if there’s other cities we can look at as precedent.

@Joe.B sorry, I should clarify. On an existing city of Austin lot we’d only be able to squeeze two townhomes since the typical lot width is 50’ w/ a 5’ side yard setback. Townhomes are wonderful, but the goal here is to get stacked fourplexes.
 
This is functionally the way it works in the Canadian code. As long as the building does not exceed 600 square meters per storey and 3 storeys in height, it can be built under requirements similar to two family units.
 
Shams Gannon said:
and removed parking minimums city wide.
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Murphy's law of unintended consequences will eventually surface if you do not have minimums in place.
Shams Gannon said:
but it may help allow smaller residential builders to get into the missing middle game.
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That is not the intent of or the purpose of the codes. No matter what you do to help increase the density the market will determine the sale or rental amounts not what code maybe used. In Montana within the states jurisdiction there are no permitting requirements for a 4-unit residential building and there is no cost savings for the purchaser or reduced rent for the tenants. Prices are always based on what the market is.
 
Joe.B said:
Where does this come from? Apologies for my ignorance on IRC, California has lots of amendments/deletions so I may not have the same language you're looking at. My code defines:

[RB] TOWNHOUSE. A building that contains three or more attached townhouse units.
[RB] TOWNHOUSE UNIT. A single-family dwelling unit in a townhouse that extends from foundation to roof and that has a yard or public way on not less than two sides.
Click to expand...
Under three unit it's either a single family dwelling or a two-family dwelling which requires 1 hour separation.
 
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