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two duplexes or a four plex

R

retire09

Silver Member
Joined
Feb 19, 2010
Messages
365
Location
Alaska
Can I build two duplexes separated by a two hour fire wall under the IRC the same as two townhouses?

I would say a four apartment building separated in the center by a two hour fire wall would create two separate buildings, each containing one duplex.

Is this contrary to the intent of the IRC?
 
May be possible. To maintain IRC applicable each building to be a dwelling must be no more than 2 dwelling units and be detached. Similar to townhouse, if each duplex is structurally independent, then two buildings and still dwelling for IRC. Structurally independent would mean the "2 hr" fire wall will be 2 walls, each on separate foundation.

Interesting proposition, are you dealing with code approval as AHJ, trying to push edge of envelope as designer, or testing opinions from peers?
 
Simple answer

NO

The IRC does not give you a prescriptive method for creating separate buildings except for townhouses and you cannot stack townhouses
 
It is important to understand that the IRC contains coverage for what is conventional and common in residential construction practice. While the IRC will provide all of the needed coverage for most residential construction, it might not address construction practices and systems that are atypical or rarely encountered in the industry.

Why not just use the IBC?
 
Where AHJ have deleted the IRC requirement for sprinklers it may beneficial.

We have allowed this as an "Attached Two-Family Dwelling". The provisions for accessibility may apply in accordance with Section R320 depending on the arrangment of dwelling units.
 
The state has amended out the sprinkler requirement so the old two hour fire wall requirement is back in play.

I know this is unusual; but if I can build a duplex up to a property line with a one hour wall and do the same on the next lot under the IRC. Why would two duplexes on the same lot with a 2 hour fire wall between them be treated any differently? A townhouse is an R-3 and so is a duplex and both by definition are dwellings. The state only requires a plan review on buildings with 4 dwellings or more. If the fire wall application is allowed, it will save plan review fees and maybe the cost of an architect for design.

The code using either the IBC or the IRC will both require the same 2 hour fire wall. The question is: do you have two duplexes (one on either side of a fire wall which creates separate buildings) under IRC or do you have a fourplex (4 dwellings in one building) under IBC?
 
The IRC does not recognize a two-hour wall except for a townhouse

You are trying to build two duplexes with zero lot line setback. R302.1 would require one-hour ASTM E 119 or UL 263 walls with exposure from both sides for each unit.

DWELLING. Any building that contains one or two dwelling units used, intended, or designed to be built, used, rented, leased, let or hired out to be occupied, or that are occupied for living purposes.

DWELLING UNIT. A single unit providing complete independent living facilities for one or more persons, including permanent provisions for living, sleeping, eating, cooking and sanitation.

LOT LINE. A line dividing one lot from another, or from a street or any public place.
 
I agree. But as described is this a 4-plex or two duplexes and able to legally avoid state plan review, plans by design professionals and qualify for the sprinkler exemption allowed for one and two family dwellings?
 
It looks like the State is calling it a 4-plex and have posted a cease and desist notice on it. The project is finished and ready to rent and now the State wants to impose their requirements on it. The building is outside of my jurisdiction but I think the builder has an unbeatable argument from a code standpoint.
 
Heard Alaska does not inspect sometimes till after a building is built?

True or not or depends on location???
 
Unfortunately almost always true except in deferred jurisdictions. The deferred jurisdictions are most but not all of the larger cities. The smaller communities and remote areas are regulated only by the State. The State does a limited plan review but few or no inspections during construction. They issue a plan review approval but no permit or certificate of occupancy. With a plan review required, but no progress inspections they have no way of knowing if all plan requirements were provided in the construction. It's dysfunctional but the best they can do under the current structure.

I personally feel that plan review is of little value without proper progress inspections.
 
R320 requires accessibility for 4 or more dwelling units in a single structure. Argument appears to hold for two family building if each duplex is a separate structure even if adjacent to each other. FHA accessibility reads the same.
 
Would six townhouses be considered six dwellings in a single structure and require compliance with chapter 11?

1103.2.4 only exempts detached dwellings.

The more you read the more complicated a seemingly simple project can become.
 
I need to get out of this business and go into a line of work more clearly understood like constitutional law. :)
 
retire09 said:
I need to get out of this business and go into a line of work more clearly understood like constitutional law. :)
Click to expand...
Than you have to talk to the US Supreme Court forum!!
 
retire09 said:
Unfortunately almost always true except in deferred jurisdictions. The deferred jurisdictions are most but not all of the larger cities. The smaller communities and remote areas are regulated only by the State. The State does a limited plan review but few or no inspections during construction. They issue a plan review approval but no permit or certificate of occupancy. With a plan review required, but no progress inspections they have no way of knowing if all plan requirements were provided in the construction. It's dysfunctional but the best they can do under the current structure. I personally feel that plan review is of little value without proper progress inspections.
Click to expand...
Ah, the Wild West where the yak and the polar bear roam
 
It's not that complicated. The IRC applicability and scope tell you what it applies to, and the definitions provide support for the text. DETACHED one- and two-family dwellings.

The intent of 'townhouses' (or 'townhomes') is for single family homes with zero lot line clearance. The wall between is match for 'party wall' in the IBC

What the OP describes is not a ResCode building.
 
Agreed. Under the IBC is it a 4-plex (R-2) or two duplexes each R-3 with a fire wall between?
 
According to Answers.com, the natural habitat of the Yak is: "The Himalayan region of Central Asia, Tibet, Mongolia and into Russia".

Maybe they crossed the Bering Sea?
 
Global warming is changing the migratory and living habits of the Yak.

International Yak Association
 
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