# Group U structure - firewall question, IBC 2009



## DB eurodirt (Aug 26, 2014)

Hello everyone.  I have a unique building situation and need assistance.  We are constructing a large open air carport.  The structure has no walls, supported by 4"x4" steel posts with an LVL/I Joist roof system.

Zero setback on one common lot line.

The structure was approved and permitted, with a requirement for a 1 hour firewall/parapet wall on one end.  Since this is a structure without any walls, I proposed class "A" roofing and 5/8" sheet rock on that end to fireproof the only combustible materials in the roof/cover.

The city would not accept this, and I appealed this decision since IBC 2009 does not seem to have anything specifically addressing this type of structure.

Can anyone tell me if they have dealt with this type issue and what, if any, arguments or points I can make to avoid this firewall.

Thanks in advance.


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## cda (Aug 26, 2014)

Well

Welcome not sure if any other public works people on the site

Bring us your knowledge


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## cda (Aug 26, 2014)

So is the only problem the combustible material ??

Not my area but see if they will accept fire retardant wood??


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## cda (Aug 26, 2014)

The city  give you any ideas??

Do they want a wall?


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## ICE (Aug 26, 2014)

The problem is that no openings are allowed.


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## cda (Aug 26, 2014)

ICE said:
			
		

> The problem is that no openings are allowed.


Build a wall?


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## steveray (Aug 26, 2014)

There is no 1hr "firewall"....And welcome....Sounds more like S2 open parking garage than U......

"Can anyone tell me if they have dealt with this type issue and what, if any, arguments or points I can make to avoid this firewall. "....Buy the adjacent lots, tear the buildings down and merge the lots?


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## cda (Aug 26, 2014)

DB eurodirt said:
			
		

> Hello everyone.  I have a unique building situation and need assistance.  We are constructing a large open air carport.  The structure has no walls, supported by 4"x4" steel posts with an LVL/I Joist roof system.Zero setback on one common lot line.
> 
> The structure was approved and permitted, with a requirement for a 1 hour firewall/parapet wall on one end.  Since this is a structure without any walls, I proposed class "A" roofing and 5/8" sheet rock on that end to fireproof the only combustible materials in the roof/cover.
> 
> ...


Is this a house or commercial building?


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## khsmith55 (Aug 26, 2014)

More information would be helpful. Is the “carport” an accessory (less than 3000sf) to a SFD or possibly an “open parking garage” (S-2) associated with an apartment or commercial building. The questions I ask is the reference to the IBC and not the IRC. If the town has classified this as a U Occupancy run with it fast and provide the one hour wall as required by Table 602. If the Town were to change their mind and classify it as an S-2, open parking garage you would be limited to Construction Types I, II, or IV (Section 406.3.3).


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## ICE (Aug 26, 2014)

cda said:
			
		

> Build a wall?


Well if no openings are allowed....that pretty much limits your options.


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## steveray (Aug 26, 2014)

ICE said:
			
		

> Well if no openings are allowed....that pretty much limits your options.


I thought mine was a good option.....


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## mtlogcabin (Aug 26, 2014)

IBC 2009 & 2012

406.3.2 Area increase.

Group U occupancies used for the storage of private or pleasure-type motor vehicles where no repair work is completed or fuel is dispensed are permitted to be 3,000 square feet (279 m2) where the following provisions are met:

1.	For a mixed occupancy building, the exterior wall and opening protection for the Group U portion of the building shall be as required for the major occupancy of the building. For such a mixed occupancy building, the allowable floor area of the building shall be as permitted for the major occupancy contained therein.

2.	For a building containing only a Group U occupancy, the exterior wall shall not be required to have a fire-resistance rating and the area of openings shall not be limited where the fire separation distance is 5 feet (1524 mm) or more.

Make sure you have at least a 5 foot setback and you are good to go


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## khsmith55 (Aug 26, 2014)

Great reference MLC. So, I guess a “carport” less than 3000sf could be called a U and over 3000sf it becomes a S-2 open parking garage? Could not find a definition of a “carport” in either the IRC or IBC. Still trying to figure out the difference between a U carport and a S-2 open parking garage?


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## cda (Aug 26, 2014)

From 2009

406.1 Private garages and carports.

406.1.1 Classification. Buildings or parts of buildings classified as Group U occupancies because of the use or character of the occupancy shall not exceed 1,000 square feet (93 m2) in area or one story in height except as provided in Section 406.1.2. Any building or portion thereof that exceeds the limitations specified in this section shall be classified in the occupancy group other than Group U that it most nearly resembles.

Whereas private garages are smaller than parking garages by definition, the impact of the fuel load represented by the vehicle is somewhat higher. Such garages are frequently attached to residential-type occupancies, with the potential for fire exposure to the residential area and the occupants therein. The code does not specifically prohibit the servicing of vehicles in private garages, since it would be impractical to enforce. For example, the occupant of a residential dwelling unit will occasionally work on a vehicle in an attached private garage. For this reason, there are special provisions for private garages.

Private garages and carports are usually considered accessory to the building they serve. Section 312 classifies these utility and miscellaneous uses as Group U. The code limits these structures to 1,000 square feet (93 m2) in area and one story in height. Those limitations correspond to a fuel load associated with the passenger motor vehicles that is matched by the specified separation requirements. Separation and construction details for private garages attached to dwelling units are provided in Section 406.1.4. This separation includes the 1/2-inch (12.7 mm) regular or 5/8-inch (15.9 mm) Type X gypsum board applied to the garage side (see Section 406.1.4 for further details).

Any garage that exceeds the height and area limits of Section 406.1.1 or the area increase of Section 406.1.2 must be reclassified. Once the specified height and area limits have been exceeded, the garage must be classified for the increased hazards. This results in the garage being classified as Group S-2, and the provisions of Sections 406.2 and 406.3 or 406.4 must now be met.

406.1.2 Area increase. Group U occupancies used for the storage of private or pleasure-type motor vehicles where no repair work is completed or fuel is dispensed are permitted to be 3,000 square feet (279 m2) when the following provisions are met:

1. For a mixed occupancy building, the exterior wall and opening protection for the Group U portion of the building shall be as required for the major occupancy of the building. For such a mixed occupancy building, the allowable floor area of the building shall be as permitted for the major occupancy contained therein.

2. For a building containing only a Group U occupancy, the exterior wall shall not be required to have a fire-resistance rating and the area of openings shall not be limited when the fire separation distance is 5 feet (1524 mm) or more.

More than one 3,000-square-foot (279 m2) Group U occupancy shall be permitted to be in the same building, provided each 3,000-square-foot (279 m2) area is separated by fire walls complying with Section 706.

The area of a private garage can be increased to 3,000 square feet (279 m2) when all of the conditions of this section are met. If the garage will only be used for the parking and storage of private or pleasure-type motor vehicles, then the area increase may be used. Care must be taken such that no repair work or fuel dispensing is done within these areas. The limitations to private- or pleasure-type motor vehicles prevent commercial motor vehicles and their increased hazards from being located in this larger private garage.

As part of the increased area provisions for private garages, the exterior walls and any openings therein must be properly protected. If the garage is part of another occupancy, then the exterior wall ratings for that occupancy apply to the garage. For example, an automobile insurance office may have several parking bays attached to it. These bays will be used to bring damaged cars in for the purposes of evaluating the damage and estimating the cost of repairs for the vehicle owner. The insurance office spaces are usually classified as Group B. In this case, the allowable building area is based on the Group B occupancy, the garage area is limited to 3,000 square feet (279 m2) and the exterior walls and openings in the garages are rated as part of the Group B occupancy.

For other applications, where the buildings only will be used to park vehicles, the building is classified as Group U. The exterior walls and openings therein are not required to be rated or limited if the fire separation distance is 5 feet (1524 mm) or more.

Additional private garages can be added to a Group U building, but they must be separated with fire walls. The 3,000-square-foot (279 m2) limit is a maximum. To reduce the risk of a fire from involving other adjacent garage spaces, fire walls are required to compartmentalize and further isolate the hazards. If the garages are located below another occupancy, such as Group R-2 apartments, the fire walls will be required to continue through to the roof of the residential portion of the building.

406.1.3 Garages and carports. Carports shall be open on at least two sides. Carport floor surfaces shall be of approved noncombustible material. Carports not open on at least two sides shall be considered a garage and shall comply with the provisions of this section for garages.

Exception: Asphalt surfaces shall be permitted at ground level in carports.

The area of floor used for parking of automobiles or other vehicles shall be sloped to facilitate the movement of liquids to a drain or toward the main vehicle entry doorway.

Carports are covered structures, either free-standing or attached to the side of a building, for the purposes of providing shelter for motor vehicles. Carports must be open on at least two sides. This allows a fire condition to vent quickly to the outside. This further prevents a fire from going undetected and usually limits the amount of other incidental storage that may be included in a fully enclosed garage. Attached carports that are not open on at least two sides are considered a garage and must then be separated from the residence or other occupancy (see Section 406.1.4 for further details).

The use of a combustible floor finish that could absorb flammable and combustible liquids commonly used and stored within garages and carports presents a potential safety hazard to the occupants of an attached building. The floors of private garages must be sloped towards the main vehicle doors. Although not specified, the floor must be positively sloped at some rate, such as 1 in 48 (2-percent slope), to prevent the accumulation of any spilled flammable and combustible liquids and their vapors. This minimizes the risk of the vapors building up to a point where a fir condition could result.


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## khsmith55 (Aug 26, 2014)

Thanks CDA, this makes everything clear.


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## cda (Aug 26, 2014)

khsmith55 said:
			
		

> Thanks CDA, this makes everything clear.


glad you understand it


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## steveray (Aug 26, 2014)

How big is it DB?....enquiring minds want to know


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## cda (Aug 26, 2014)

Do you think DB will ever ask a question again? After he sees all the responses


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## DB eurodirt (Aug 27, 2014)

The Carport is 1344 sf.  I really appreciate the responses...it seems that we will be stuck with a firewall on the end, since moving in 5' is not an option (it would make the space to small between the last two posts).  I really hoped there was an exception of some kind...

Thanks all!


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## cda (Aug 27, 2014)

DB eurodirt said:
			
		

> The Carport is 1344 sf.  I really appreciate the responses...it seems that we will be stuck with a firewall on the end, since moving in 5' is not an option (it would make the space to small between the last two posts).  I really hoped there was an exception of some kind...Thanks all!


simple cmu brick wall???


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## DB eurodirt (Aug 27, 2014)

Perhaps.  I need to check with Town and see what they will permit.  Will Class "A" roofing on that end negate the Parapet wall requirement?


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## cda (Aug 27, 2014)

delete delete


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## cda (Aug 27, 2014)

DB eurodirt said:
			
		

> Perhaps.  I need to check with Town and see what they will permit.  Will Class "A" roofing on that end negate the Parapet wall requirement?


does not sound like it, but ask the city cannot hurt, or propose fire retardant wood


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## DB eurodirt (Aug 27, 2014)

Will Class "A" roofing negate the Parapet wall requirement?


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## DB eurodirt (Aug 27, 2014)

Also, does anyone know if there is a fire rating for metal?  I though perhaps putting that heaving gauge "Rusty Metal" roofing material on the end for the fire wall??


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## mtlogcabin (Aug 27, 2014)

705.11 Parapets.

Parapets shall be provided on exterior walls of buildings.

Exceptions: A parapet need not be provided on an exterior wall where any of the following conditions exist:

1.	The wall is not required to be fire-resistance rated in accordance with Table 602 because of fire separation distance .

2.	The building has an area of not more than 1,000 square feet (93 m2) on any floor.

3.	Walls that terminate at roofs of not less than 2-hour fire-resistance-rated construction or where the roof, including the deck or slab and supporting construction, is constructed entirely of noncombustible materials.

4.	One-hour fire-resistance-rated exterior walls that terminate at the underside of the roof sheathing, deck or slab, provided:

4.1.	Where the roof/ceiling framing elements are parallel to the walls, such framing and elements supporting such framing shall not be of less than 1-hour fire-resistance-rated construction for a width of 4 feet (1220 mm) for Groups R and U and 10 feet (3048 mm) for other occupancies, measured from the interior side of the wall.

4.2.	Where roof/ceiling framing elements are not parallel to the wall, the entire span of such framing and elements supporting such framing shall not be of less than 1-hour fire-resistance-rated construction.

4.3.	Openings in the roof shall not be located within 5 feet (1524 mm) of the 1-hour fire-resistance-rated exterior wall for Groups R and U and 10 feet (3048 mm) for other occupancies, measured from the interior side of the wall.

4.4.	The entire building shall be provided with not less than a Class B roof covering.


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