# two duplexes or a four plex



## retire09

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?


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## jdfruit

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?


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## mtlogcabin

Simple answer

NO

 The IRC does not give you a prescriptive method for creating separate buildings except for townhouses and you cannot stack townhouses


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## mtlogcabin

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?


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## Francis Vineyard

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.


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## steveray

mtlogcabin said:
			
		

> Why not just use the IBC?


Sprinklers..


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## retire09

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?


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## retire09

Even if you review it all under the IBC; is it a four-plex or two duplexes?


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## mtlogcabin

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.


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## retire09

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?


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## cda

May be a state question??

Drop a call? Can't hurt


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## retire09

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.


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## cda

Heard Alaska does not inspect sometimes till after a building is built?

True or not or depends on location???


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## retire09

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.


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## jdfruit

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.


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## retire09

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.


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## retire09

I need to get out of this business and go into a line of work more clearly understood like constitutional law.


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## cda

retire09 said:
			
		

> I need to get out of this business and go into a line of work more clearly understood like constitutional law.


Than you have to talk to the US Supreme Court forum!!


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## cda

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.


Ah, the Wild West where the yak and the polar bear roam


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## JBI

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.


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## retire09

Agreed. Under the IBC is it a 4-plex (R-2) or two duplexes each R-3 with a fire wall between?


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## north star

*& ~ ~ & ~ ~ &*



They have "yak" in Alaska ?   :-o

*& ~ ~ & ~ ~ &*


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## JBI

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?


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## cda

Global warming is changing the migratory and living habits of the Yak.

International Yak Association


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## mtlogcabin

north star said:
			
		

> *& ~ ~ & ~ ~ &*
> 
> They have "yak" in Alaska ?   :-o
> 
> 
> 
> *& ~ ~ & ~ ~ &*


We have Yaak in montana

http://en.wikipedia.org/wiki/Yaak,_Montana

Rumor has it some of the "residents" are under the witness protection. The remaining are related to "Rambo" and provide the protection.


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## north star

*( ~ ~ ~ ~ )*

cda,

Global Warming is no longer the politically correct term.

Nowadays,  the Spin-meisters are using the term "Climate Change" to

lubricate their agendas.........Just saying...

*( ~ ~  ~ ~ )*


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## north star

*& = = = &*

Well, this OP has gotten off-track and deep in to the weeds.

I'm going to eject now, before I flame out.

See ya...     

*& = = = &*


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## Francis Vineyard

FIRE SEPARATION DISTANCE. The distance measured

from the building face to one of the following:

1. To the closest interior lot line; or

2. To the centerline of a street, an alley or public way; or

3. To an imaginary line between two buildings on the lot.

The distance shall be measured at a right angle from the

face of the wall.

R302.1 Exterior walls. Construction, projections, openings

and penetrations of exterior walls of dwellings and accessory

buildings shall comply with Table R302.1(1); or dwellings

equipped throughout with an automatic sprinkler system

installed in accordance with Section P2904 shall comply

with Table R302.1(2).

*TABLE R302.1* *EXTERIOR WALLS *


*EXTERIOR WALL ELEMENT**MINIMUM*

*FIRE-RESISTANCE RATING**MINIMUM FIRE* *SEPARATION DISTANCE*Walls(Fire-resistance rated)1 hour-tested in accordance with ASTM E 119 or UL 263 with exposure from both side< 5 feet

"The exterior rated walls should be tested in accordance with either ASTM E 199 or UL 263.  This is not intended to limit fire-resistance-rated assemblies solely to the test criteria contained in these standards.  Section R104.11 still allows the building official to approve alternative fire-resistance methodologies, such as those described in Section 703.3 of the IBC.  This would still allow a builder to use acceptable engineering analysis, calculations in accordance with Section 721 of the IBC or prescriptive assemblies permitted by Section 720 of the IBC as alternatives tot he standards contained within the code."

*R104.11 Alternative materials, design and methods of construction and equipment. *The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been _approved. _An alternative material, design or method of construction shall be _approved _where the _building official _finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code. Compliance with the specific performance-based provisions of the International Codes in lieu of specific requirements of this code shall also be permitted as an alternate.


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## jdfruit

FV & Retire;

Appears the argument for detached duplex is still alive if each is a separate structure. See post #2 & #15

If two hr party wall on common foundation then "detached" is not provided

Retire; do you know the actual construction condition at "2hr" as described in your OP?


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## retire09

I have not seen the building myself but the builder tells me he has a two hour fire wall with two apartments on each side. Assuming that is correct;

I would say the building does not qualify for construction under the IRC because the two units on each side of the fire wall are not detached and therefore not exempt from the IBC per 101.2 exception.

So, per the IBC we have two separate buildings, separated by a fire wall. Each building contains only two dwelling units which by definition is still an R-3. It is not a duplex and not a townhouse but still an R-3. A two dwelling unit building on each side. Not an R-2 or a 4-plex.

Make sense?


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## cda

Can they make the complex a townhouse ???


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## retire09

A townhouse is a single dwelling unit and we have two units on each side with a 1 hour separation between.

Not a townhouse because not one dwelling,

Not a duplex because not detached

R-3  Buildings that do not contain more than two dwelling units.


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## cda

retire09 said:
			
		

> A townhouse is a single dwelling unit and we have two units on each side with a 1 hour separation between.Not a townhouse because not one dwelling,
> 
> Not a duplex because not detached
> 
> R-3  Buildings that do not contain more than two dwelling units.


Add another layer of Sheetrock and divide into individual units ?? So there are town houses?


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## jdfruit

Per the federal housing guidelines, accessiblity is required if this is an IBC residential building

"Covered multifamily dwellings" or "covered multifamily dwellings subject to the Fair Housing Amendments" means buildings consisting of four or more dwelling units if such buildings have one or more elevators; and ground floor dwelling units in other buildings consisting of four or more dwelling units. Dwelling units within a single structure separated by firewalls do not constitute separate buildings.


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## mtlogcabin

The IBC is a very specific about Fire Walls and their construction. I would bet the construction meets the definition of a Fire Barrier and not a Fire Wall as defined by the IBC therefore they would not be separate buildings and an R-3

See Section 706.2, 706.5.1, 706.5.2, 706.6 and possibly 706.6.1


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## retire09

Alaska State plan review does not include accessibility requirements.

See at the state web site  http://www.dps.state.ak.us/Fire/PRB/


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## Francis Vineyard

So 101.2 exception literally allows the use of IRC if the two-family dwelling exterior walls are against one another but need to use IBC if constructed with a common wall for separate buildings?


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## retire09

I don't know why, but yes.


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## jdfruit

retire09 said:
			
		

> Alaska State plan review does not include accessibility requirements.See at the state web site  http://www.dps.state.ak.us/Fire/PRB/


Wow! Dude! no accessibility or structural review. Who does the code enforcement for structural and accessibility?


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## cda

jdfruit said:
			
		

> Wow! Dude! no accessibility or structural review. Who does the code enforcement for structural and accessibility?


Gets the polar bear "seal" of approval.  Unless it needs a special "yak inspection"

""""""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."""""


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## retire09

After all, we are the last frontier.


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## JBI

A fire wall must start at the lowest point (basement floor or slab on grade) and extend full height uninterrupted through or to the roof deck. Many, many people, DP's and Contractors as well as John Q. Public use the term fire wall waaaaay too often and for the wrong assembly more often than not.

The building in the OP may well have 2 two dwelling unit buildings within one structure properly divided by a fire wall and regulated as R-3 under the IBC, but it is not 2 detached two-family dwellings within the context of the IRC.


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## mtlogcabin

jdfruit said:
			
		

> Wow! Dude! no accessibility or structural review. Who does the code enforcement for structural and accessibility?


It is handled by the fire division. They are not concerned about trivial things such as accessibility or structural concerns. Sprinklers cover all of that


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## Francis Vineyard

Attached single family dwelling that's neither a two-family or town house also does not meet 102.1 exception?


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## retire09

Only detached one and two family and townhouses are exempt. This is an attached two family and therefore technically is not exempt.

But it is still two R-3 buildings if the fire wall is built correctly.


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## Francis Vineyard

The point is it makes no sense for even two single family dwellings attached to be an R-2 instead of R-3.


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## Buelligan

*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 at least two sides_.

I have what is essentially two duplexes attached being called "Villas". Single story dwelling units on a slab. Each unit is on a separate lot and has it's own front and back yard. each unit is separated by a 2-hour fire wall. Not one wall separating the "duplexes" but a full 2- hour wall between each unit.

Does this not meet the definition of townhouse pasted above?

I am requiring a sprinkler system per 313 and with that, could they not build a 1-hour "common wall" under the following exception?

*R302.2 Townhouses.* Each townhouse shall be considered a separate building and shall be separated by fire-resistance-rated wall assemblies meeting the requirements of Section R302.1 for exterior walls.

*Exception: A common 1-hour fire-resistance-rated wall assembly tested in accordance with ASTM E 119 or UL 263 is permitted for townhouses if such walls do not contain plumbing or mechanical equipment, ducts or vents in the cavity of the common wall. The wall shall be rated for fire exposure from both sides and shall extend to and be tight against exterior walls and the underside of the roof sheathing. Electrical installations shall be installed in accordance with Chapters 34 through 43. Penetrations of electrical outlet boxes shall be in accordance with Section R302.4.*


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## Francis Vineyard

Bulligan,

The duplex must be detached or constructed with separate exterior walls to be allowed under the IRC, if constructed with a common or shared wall it must be constructed in accordance with the IBC.

Commentary; "(Duplexes, buildings with two dwelling units, must be detached from other structures in order to be regulated by the IRC.) A duplex attached to another duplex would be required to comply with the code and be classified as Group R-2 or R-3, depending on the presence of fire walls."


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## JBI

Francis, Buelligan is asking about a different project than the OP (retire09).

Buellgan, In answer to your question, Yes they qualify as 'townhouses' under the IRC.


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## mtlogcabin

> I have what is essentially two duplexes


This is confusing

I think you are saying you have a 4 unit Townhouse and can the common each  wall between each unit be reduced to one-hour if all the units are sprinkled?

Answer: yes


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## Buelligan

The above is how they are laid out. They for all intent and purposes are sold and marketed as "duplexes" and look more like that than the traditional "3-story" townhouse. But by my understanding it falls very clearly in the IRC "definition" of a townhouse.

So let me pose this question. Considering the separation and lot lines could this still be submitted under R-3?


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## Buelligan

mtlogcabin said:
			
		

> This is confusingI think you are saying you have a 4 unit Townhouse and can the common each  wall between each unit be reduced to one-hour if all the units are sprinkled?
> 
> Answer: yes


Yes that is what I am saying. Just not sure because of the "Marketing Term" used. They are being sold as "Villas" and even using the term "Duplexes". I guess because they are not your typical skinny 3-story townhomes they are more like 4 attached ranchers if you will.


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## Francis Vineyard

Well I'm (was) confused; I thought a duplex is another name for 2-family dwelling.  Townhouses are 3 or more attached single family dwellings.

Four attached ranchers would be under IRC and also Chapter 11 of IBC; unless they've deleted R320


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## mtlogcabin

Remember to qualify as a townhouse the fire rated wall has to extend from the foundation to the roof deck and parapets need to be installed or the exceptions need to be followed.


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## retire09

You do not have duplex townhouses. You have two,  R-3, two dwelling unit buildings separated by a 2 hour fire wall.

You can call them Villas but they are technically not townhouses or duplexes. They are compliant with the IBC and do not qualify for construction per the IRC.

It all makes perfect sense if you don't think about it.


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## jdfruit

Trail braked and didn't see it coming, now off in the sand pit

Post #51 shows 4 lots and 4 homes with 2hr firewalls on property lines = 4 townhomes. Marketing terminology is not accurate, code definitions are applicable to code discussions.


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## Buelligan

retire09 said:
			
		

> You do not have duplex townhouses. You have two,  R-3, two dwelling unit buildings separated by a 2 hour fire wall.You can call them Villas but they are* technically not townhouses *or duplexes. They are compliant with the IBC and do not qualify for construction per the IRC.
> 
> It all makes perfect sense if you don't think about it.


Why would they not "technically" be townhomes? In this case they meet the definition posted above EXACTLY - 3 or more attached with yards on 2 sides.

I absolutely understand that "Marketing terms" are not relevant to code but it gets a little worrisome when these look like and are sold as attached "Duplexes" even if they call them "Villas". I felt comfortable with my decision to consider them "townhouse" by code definition, regardless of any "terms" used.

The reason this is an issue is that our state adopted 2009 with an amendment to 313 for One and Two Family dwellings that gives alternatives to sprinklers. But they left Townhomes out of the amendment! This contractor is upset because as he states, "these are not townhomes". But I got him to understand that it is not a One and Two Family dwelling and that it is either a townhouse or he can use the IBC R-3. Either way he has to sprinkle these units.


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## retire09

A townhouse is attached single family with a fire wall between each. A duplex is detached two family.

It is my understanding, you have two units on each side of a fire wall.

Not being single family, it is not a townhouse.

Not being detached it is not a duplex.

It is still an R-3 per IBC


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## steveray

The drawing in post 51 looks like it could be a townhouse to me...


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## retire09

I have not seen a drawing; but if all individual dwelling units have the required fire wall separations; they are townhouses.

If the fire wall is only provided at every other unit they are not.


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## JBI

The ORIGINAL POST was about 2 duplexes on adjoining lots with a 2 hour wall.

BUELLIGAN's post is about a DIFFERENT scenario.

OP is NOT townhouses, Buelligan's are.


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## TJacobs

JBI said:
			
		

> The ORIGINAL POST was about 2 duplexes on adjoining lots with a 2 hour wall. BUELLIGAN's post is about a DIFFERENT scenario.
> 
> OP is NOT townhouses, Buelligan's are.


Exactly!  Two different scenarios...two different answers.


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## Buelligan

Thanks guys!

One question though. In the OP, would the duplexes on either side of the "center" wall be required to be separated by 2- hour as well? or did I miss something, like them being stacked or are they all on the same lot maybe? Just curious


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## JBI

Buelligan, The OP had duplexes on adjoining lots with zero lot line clearance. Honestly, I'd have to check the IBC for required rating and limitations, but I think the 2-hour wall and limited mechanicals would comply depending on construction type (sprinklers would be a given for a new R occupancy in IBC).


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## retire09

The two unit buildings are separated by a two hour fire wall the individual units are separated by the required one hour between dwellings.


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