Duplex Garage Separation

[Paul Legan]

I'm working on a duplex with a detached garage. The detached garages sit behind the dwellings, and are, like the dwelling, connected by a demising wall. Does anyone know a code provision that requires the garages have a fire separation between one another?

 

[Paul Legan]

I may be on the right track... 2015 IRC states (R302.3) that dwelling units shall be separated by 1-hour. Since a garage isn't a dwelling unit, and the garages connect on a property line, then must one consider them as 2-buildings within 5' fire separation per Table R302.1(1)?

 

[JCraver]

If there is a platted property line down the middle of the wall dividing them then yes, they're 2 separate buildings per the code.

 

[Paul Legan]

If there is a platted property line down the middle of the wall dividing them then yes, they're 2 separate buildings per the code.

Thank you, and in your interpretation, is the required separation per R302.1(1)? (granted that there isn't something local overriding that.)

 

[Sleepy]

If it is just a duplex, without a property line between, then I don't see why you would have to consider the two garage spaces as separate buildings. You could easily have a two car garage with Tenant A assigned to one side and Tenant B assigned to the other with no wall at all between them. On the other hand, if it is a townhouse situation with an actual property line between, then I think some sort of separation or rated fire wall would be required.

 

[classicT]

Key statement, these are detached garages. As such, will either need to comply with Table R302.1(1), which requires two 1hr rated walls (two walls required as they need to be structurally independent) due to <5ft seperation, if a property line bisects the garage(s), or be on the same lot and have no required separation between garage units as it is considered to be one building (similar to apartment garage units).

Sections R302.2 and R302.3 do not apply, as these only relate to the dwelling units.

 

[my250r11]

A sketch would help.

 

[JCraver]

It depends entirely on if there's a platted, recorded property line or not. Conventional duplex vs. townhouse, like Sleepy said.

Property line + different owner on each side = 2 separate buildings. 2 separate buildings less than 5' apart = 1 hr. wall in the middle.

No property line + same owner each side = build it like a garage, and put a dividing wall in the middle if you want to. One building + one owner = no separation required.

 

[JCraver]

Key statement, these are detached garages. As such, will either need to comply with Table R302.1(1), which requires two 1hr rated walls (two walls required as they need to be structurally independent) due to <5ft seperation, if a property line bisects the garage(s), or be on the same lot and have no required separation between garage units as it is considered to be one building (similar to apartment garage units).

Sections R302.2 and R302.3 do not apply, as these only relate to the dwelling units.

I don't think this is right? I don't see anything in Table 302.1(1) which requires there to be 2 one-hour walls. If it were a townhouse then they'd need to be structurally independent, but this is a detached garage we're talking about.

 

[classicT]

I don't think this is right? I don't see anything in Table 302.1(1) which requires there to be 2 one-hour walls. If it were a townhouse then they'd need to be structurally independent, but this is a detached garage we're talking about.

The code does not provide a provision for other than townhouses. A detached garage does not meet the definition of a townhouse. How could a single structure cross a property line and be owned by two separate owners? If they share a common wall, it is a single structure.

Option 1 - Independent structures on each respective property, each structurally independent with 1hr walls.
Option 2 - One structure,one lot, one owner, and no separation required.

 

[Paul Legan]

Sorry, I tried to post a sketch but the link kept appearing broken.

In my instance, the property is divided in half per plat, between the duplexes.

 

[Sleepy]

Sorry, I tried to post a sketch but the link kept appearing broken.

In my instance, the property is divided in half per plat, between the duplexes.

Then you could look at IRC R302.2 (in the 2015 edition) for common walls separating townhouse walls and/or IBC 706.1.1 (2015 edition) for party walls.

 

[ICE]

Smother the wall with type X drywall....nail the roof sheathing to the top plate.... if either side burns away the other side will keep the wall up.

Of course that's only if you have to.....if you don't have to you might try: Smother the wall with type X drywall....nail the roof sheathing to the top plate.... if either side burns away the other side will keep the wall up.

 

[Paul Legan]

Smother the wall with type X drywall....nail the roof sheathing to the top plate.... if either side burns away the other side will keep the wall up.

Of course that's only if you have to.....if you don't have to you might try: Smother the wall with type X drywall....nail the roof sheathing to the top plate.... if either side burns away the other side will keep the wall up.

Haha, you can't be wrong if every wall is 2-hour!!

Thanks all for your time and responses!, the topic is clearer for me now.

 

[Mr. Inspector]

To make it more confusing what if these garages are garage condos?

 

[mtlogcabin]

In my instance, the property is divided in half per plat, between the duplexes.

You do not meet exception 2 therefore R302 is applicable and a 1-hour wall rated from both sides is required. See Table R302.1(1)


SECTION R302
FIRE-RESISTANT CONSTRUCTION

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).

Exceptions:

1. Walls, projections, openings or penetrations in walls perpendicular to the line used to determine the fire separation distance.

2. Walls of dwellings and accessory structures located on the same lot.

3. Detached tool sheds and storage sheds, playhouses and similar structures exempted from permits are not required to provide wall protection based on location on the lot. Projections beyond the exterior wall shall not extend over the lot line.

4. Detached garages accessory to a dwelling located within 2 feet (610 mm) of a lot line are permitted to have roof eave projections not exceeding 4 inches (102 mm).

5. Foundation vents installed in compliance with this code are permitted.

 

[classicT]

You do not meet exception 2 therefore R302 is applicable and a 1-hour wall rated from both sides is required. See Table R302.1(1)

Two one hour walls are required - a building cannot extend over the property line, therefore two independent structures must be built, each of 1hr construction.

 

[mtlogcabin]

My bad yes 2 one-hour walls are required
thanks for catching the mistake