# Wall requirement if duplex gets lot split?



## Pcinspector1 (Jul 21, 2010)

If a duplex meets all the requirements for a lot split, what requirements are there for the seperation wall?


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## fatboy (Jul 21, 2010)

Less than 5' to property line = each wall must be a separate 1-HR wall.

Or, view it as a townhouse and comply with those requirement.


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## Mule (Jul 21, 2010)

It wouldn't fall under the definition of a townhouse. You need to use section R317  Dwelling Unit Separation.

The code says "by wall" I do not think that means two separate walls.

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....

This "wall" would need to go through the attic space unless Exception 2 can be applied.

2. Wall assemblies need not extend through attic spaces

when the ceiling is protected by not less than 5/8-inch

(15.9 mm) Type X gypsum board and an attic draft

stop constructed as specified in Section R502.12.1 is

provided above and along the wall assembly separating

the dwellings. The structural framing supporting

the ceiling shall also be protected by not less than 1/2

-inch (12.7 mm) gypsum board or equivalent.


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## fatboy (Jul 21, 2010)

If there is a property line separating a duplex, we consider them to be separate buildings, thus two 1-HR walls.

I understand what a townhouse is, I was just saying that one could propose to use those separation requirements.


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## Yankee (Jul 21, 2010)

If is it to be lot split, it needs to be a townhouse. If left as a duplex, then the 1 hr wall. This isn't really a zoning question though, it is a building code question based on the property line location.


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## FredK (Jul 21, 2010)

It's not a townhouse.  TOWNHOUSE. A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides.

It's a dwelling.   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.

So if this is and older unit no seperation required.  If a new building I go with the wall closer than 5 ft need 1hr ratings for both walls.


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## mtlogcabin (Jul 21, 2010)

It all boils down to will you accept a common 2-hour wall or require 2 one hour walls. Our local zoning code calls 2 attached dwelling units with a property line seperating them and open on 2 sides a townhouse. Use R104.10 Modifications.

Wherever there are practical difficulties involved in carrying out the provisions of this code, the building official shall have the authority to grant modifications for individual cases, provided the building official shall first find that special individual reason makes the strict letter of this code impractical and the modification is in compliance with the intent and purpose of this code and that such modification does not lessen health, life and fire safety requirements or structural. The details of action granting modifications shall be recorded and entered in the files of the department of building safety.


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## fatboy (Jul 21, 2010)

my point exactly mt.........

I know where the definitions are in the code, I was talking about a practical modification proposal.


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## mtlogcabin (Jul 21, 2010)

> So if this is and older unit no seperation required. If a new building I go with the wall closer than 5 ft need 1hr ratings for both walls.


Once they drop a property line thru this building then a one hour wall is required for EACH dwelling unit

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.

R302.1 Exterior walls.

TABLE R302.1

EXTERIOR WALLS EXTERIOR WALL ELEMENT MINIMUM FIRE-RESISTANCE RATING MINIMUM FIRE SEPARATION DISTANCE

We allow the 2-hour common wall as posted above because it is the simplest way to achieve adequate seperation between the units. The wall extends to the bottom of the roof deck, 5/8 type X is installed on the bottom of the roof sheating 4 ft out and all roof penetrations with in the 4 ft are relocated. It is a simple cost effective solution.


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## Mule (Jul 21, 2010)

Okay...teach me something. Why would you need two walls. Section 302 specifies Exterior Walls. Table R302.1 Exterior Walls....states 1 hour with exposure on both sides. If you have one wall that is one hour construction wouldn't that give you the separation.

Why is the party wall between the two dwellings considered an exterior wall? The definition of an exterior wall is..

EXTERIOR WALL. An above-grade wall that defines the

exterior boundaries of a building.

Just because you have a lot line running down the middle of a building does not mean that that wall is the exterior wall of a building... Does it?

Learn me something here please...


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## Pcinspector1 (Jul 21, 2010)

Added info:

Duplex with two walls, with 5/8" fire rock on each units side with fiberglas insulation in each wall into the attic to the bottom of the roof sheeting all taped and sealed by not through the roof. PnZ did not like this and questioned why the wall does not have to extend through the roof. Questions like, "Does this allow one of the homeowners to roof his side with a different colored shingle or paint his side differently?

My Responce is: Yes it does! No covenants on colors or materials!


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## Pcinspector1 (Jul 21, 2010)

mtlogcabin,

The drywall extending 4' from the party (seperation wall) in the attic is done on 4-plexes as they are sold to individual owners with the seperation walls being built the same way as the duplex walls as I posted. I'am not sure why the duplexes do not have the 4ft drywall below the roof deck. Another area like the floor cavity has to blocked also between units with solid blocking and drywall.


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## Yankee (Jul 21, 2010)

FredK said:
			
		

> It's not a townhouse.  TOWNHOUSE. A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides.It's a dwelling.   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.


You are right, I agree, it is a duplex even if property line is between the to. Must be careful not to mix up the code definition of Townhouse with anybody else's zoning definition of Townhouse. Gets me sometimes (and try explaining it to real estate salesperson).


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## TimNY (Jul 21, 2010)

I would think they each need their own wall.  What happens if i want to tear down my half?

My interpretation is that neither party has an exterior wall.  They each have half an exterior wall


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## FredK (Jul 21, 2010)

Well like I said if it's an older unit my stand is nothing needed.  If they want to come in with a new plan it's got to meet R317 for seperation.

As it is I have some new duplex constructed where they built one side only.  Their solution was a brick wall down the middle and then 2 seperate truss sheeted both sides with 5/8 type x place on the brick wall.

Ought to be a hoot when they start building on the unbuilt side.  Can just hear the next door guy calling and asking me to do something about the noise or start times.


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## peach (Jul 21, 2010)

a duplex will probably only have a one hour separation, (maybe)... zero lot line requires 1 hour from each side... the fire exposure from each side.

With a 2 family dwelling, it's not an exterior wall.  Split the units, it is.


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## JBI (Jul 21, 2010)

Gotta go with mtlog & peach on this one. Something 'changed' to create a requirement. It may be an imaginary line on a map, but it creates a new situation and the separation distance provisions kick in. TimNY, I think you're half right - they currently have a half a wall each, but they will require a whole wall each to comply.


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