# Two Family Dwelling Unit????



## righter101 (Nov 16, 2010)

What would constitute a "2 family dwelling unit" or a "duplex".  What would be considered a single "structure" or "building"???

The reason is one of our zonings (Rural Farm Forest (RFF)) allows a "duplex" to be built.  An applicant is proposing to build 2 houses, separate, with a connecting breezeway (covered porch type strucutre) and sharing a common roof line.  Would this make a single "structure"???

What if the connecting piece was entirely enclosed and conditioned??

Thoughts???


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## bldginsp (Nov 16, 2010)

A duplex would have to have some type of fire separation, either horizontal or vertical.  From the IRC: Dwelling units in two-family dwellings shall be separated from each other by wall and/or floor assemblies having not less than a 1-hour fire-resistance rating when tested in accordance with ASTM E 119. Fire-resistance-rated floor-ceiling and wall assemblies shall extend to and be tight against the exterior wall, and wall assemblies shall extend to the underside of the roof sheathing.  Other items to consider are height and story, etc.  Since you have the connecting breezeway, if it is properly fire rated you have a duplex.  However, no breezeway make's it two independent structures.  These would not be able to be two family in the same building or now you would have a 4 plex.  JMO.


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## righter101 (Nov 16, 2010)

Basically what the applicant is attempting to do is build 2 separate residences, under the banner of a "duplex" and they wish to have them quite a ways apart, connected with a breezeway or enclosed long hallway.

would you allow that as a "duplex" or is it 2 SFR's???

The definitions don't really give me enough to say for certain either way so I was trying to get other opinions.

thanks for the feed back.


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## cboboggs (Nov 16, 2010)

How does your zoning code define duplex? I would have to say that as long as the buildings have the proper fire rated separation at somepoint, then it is a two family dwelling.


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## bldginsp (Nov 16, 2010)

We have had to "attach" buildings in order to meet zoning requirements because of lot size.  As long as they are attached we classify them as duplex for two or R-2, R-3 if applicable.  Again the fire separation comes into play.


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## righter101 (Nov 16, 2010)

Our zoining definitions include the following gems:

1) Duplex.  See "Dwelling unit, two family."

2) Dwelling unit, two-family (duplex)" means a structure containing two dwelling units.

The fire separation is no question.  I am wondering if the units have to have conditioned space connecting them, or if a covered breezeway would suffice.


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## Yankee (Nov 16, 2010)

Often the dwelling units of a duplex are divided by the garage (for each). Otherwise, I'd set some local standard for yourself. We have a standard that requires a four season connection that is more than a hallway/walkway (about "room" proportion) between a dwelling and its "in-law" apartment. Similar situation I think.


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## bldginsp (Nov 17, 2010)

I agree with Yankee in your zoning in setting some type of standard.  Folks these days have creative ideas.  Good luck.


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## brudgers (Nov 17, 2010)

righter101 said:
			
		

> What would constitute a "2 family dwelling unit" or a "duplex".  What would be considered a single "structure" or "building"???The reason is one of our zonings (Rural Farm Forest (RFF)) allows a "duplex" to be built.  An applicant is proposing to build 2 houses, separate, with a connecting breezeway (covered porch type strucutre) and sharing a common roof line.  Would this make a single "structure"???
> 
> What if the connecting piece was entirely enclosed and conditioned??
> 
> Thoughts???


First, what motivates you to deny this?

Second, if it is not a two-family dwelling does that mean you would allow it in a single-family zoning district?


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## righter101 (Nov 18, 2010)

You assume that I am motivated to deny this.  I don't want someone to construct 2 separate houses on a parcel where only one is allowed, have them 500 feet apart, connect them with a piece of ribbion, and call it a duplex.

Part 2 of your question, if it was considered 2 separate single family dwellings, only one of them would be allowed on in single family zoning.

I am motivated to approve this.  I actually use "milton's rule" and look for ways to approve things.  I don't however, want to approve something that shouldn't be allowed.


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## Architect1281 (Dec 11, 2010)

I really hate to do this because I never encourage cross code definition but as One and two family does not adress building area specifically this would work for me

From IBC 502

AREA, BUILDING. The area included within surrounding exterior walls (or exterior walls and fire walls) exclusive of

vent shafts and courts. Areas of the building not provided with surrounding walls shall be included in the building area if such

areas are included within the horizontal projection of the roof or floor above.

and that area could be very narrow like a covered walk

similar definitions may also be addressed in zoning

I intend to use this myself when I place an accessory dwelling unit / home office above a nearby detached garage to qualify it as a single structure


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