What is the minimum separation: Dwelling to property line?

[Jerry Peck - Codeman]

(From an e-mail question.)

Codeman,

What is the minimum required fire separation between a dwelling unit and its closest property line?

Are openings (such as windows and doors) allowed in that wall?

Are penetrations (such as exhaust fan discharges) allowed in that wall?

Is that wall required to be fire-resistance rated?

Thanks,

D.G

[Jerry Peck - Codeman]

Hi D.G.,

That's not only a lot of questions, but the answers are also complex, albeit intertwined with each other (to a degree).

The code I will reference is the International Residential Code (IRC) as most AHJ (Authorities Having Jurisdiction) have adopted the IRC for residential construction (construction of one-and two-family dwellings and townhouses) 3 or fewer stories high.

The 2006 IRC, in Table R302.1 states:

- Table R302.1
- - Exterior Walls
- - - Exterior Wall Element
- - - - Walls - Fire resistance rated - 1 hour rating exposure both sides - 0 feet separation allowed
- - - - Walls - Not Fire resistance rated - 0 hour rating - 5 feet or more separation required
- - - - Projections - Fire resistance rated - 1 hour rating on underside - 4 feet separation required
- - - - Projections - Not Fire resistance rated - 0 hour rating - 5 feet or more separation required
- - - - Openings - Not allowed - N/A - with <3 feet separation provided
- - - - Openings - 25% maximum of wall area - 0 hours rating - with 3-5 feet separation provided
- - - - Openings - Unlimited - 0 hours rating - with 5 feet or more separation provided
- - - - Penetrations - All - Fire-resistance rating to comply with Section R317.3 - when <5 feet separation provided
- - - - Penetrations - All - No Fire-resistance rating Required - with 5 feet or more separation provided

The wall you show in the photo attached to your e-mail shows there is a penetration on the side facing the adjacent building to the right and that there is <5 feet separation provided to the property line on the right, which is also the left wall of the building on the right. That means the fire-resistance rating of the penetration needs to comply with Section R317.3. (see my underlining above)

- R317.3 Rated penetrations. Penetrations of wall or floor/ceiling assemblies required to be fire-resistance rated in accordance with Section R317.1 or R317.2 shall be protected in accordance with this section.
- - R317.3.1 Through penetrations. Through penetrations of fire-resistance-rated wall or floor assemblies shall comply with Section R317.3.1.1 or R317.3.1.2.
- - - Exception: Where the penetrating items are steel, ferrous or copper pipes, tubes or conduits, the annular space shall be protected as follows:
- - - - 1. In concrete or masonry wall or floor assemblies where the penetrating item is a maximum 6 inches (152 mm) nominal diameter and the area of the opening through the wall does not exceed 144 square inches (92 900 mm2), concrete, grout or mortar is permitted where installed to the full thickness of the wall or floor assembly or the thickness required to maintain the fire-resistance rating.
- - - - 2. The material used to fill the annular space shall prevent the passage of flame and hot gases sufficient to ignite cotton waste where subjected to ASTM E 119 time temperature fire conditions under a minimum positive pressure differential of 0.01 inch of water (3 Pa) at the location of the penetration for the time period equivalent to the fire resistance rating of the construction penetrated.
- - - R317.3.1.1 Fire-resistance-rated assembly. Penetrations shall be installed as tested in the approved fire-resistance-rated assembly.
- - - R317.3.1.2 Penetration firestop system. Penetrations shall be protected by an approved penetration firestop system installed as tested in accordance with ASTM E 814 or UL 1479, with a minimum positive pressure differential of 0.01 inch of water (3 Pa) and shall have an F rating of not less than the required fire-resistance rating of the wall or floor/ceiling assembly penetrated.
- - R317.3.2 Membrane penetrations. Membrane penetrations shall comply with Section R317.3.1. Where walls are required to have a fire-resistance rating, recessed fixtures shall be so installed such that the required fire resistance will not be reduced.
- - - Exceptions:
- - - - 1. Membrane penetrations of maximum 2-hour fire-resistance-rated walls and partitions by steel electrical boxes that do not exceed 16 square inches (0.0103 m 2) in area provided the aggregate area of the openings through the membrane does not exceed 100 square inches (0.0645 m2) in any 100 square feet (9.29 m2) of wall area. The annular space between the wall membrane and the box shall not exceed 1/8 inch (3.1 mm). Such boxes on opposite sides of the wall shall be separated as follows:
- - - - - 1.1. By a horizontal distance of not less than 24 inches (610 mm) except at walls or partitions constructed using parallel rows of studs or staggered studs;
- - - - - 1.2. By a horizontal distance of not less than the depth of the wall cavity when the wall cavity is filled with cellulose loose-fill, rockwool or slag mineral wool insulation;
- - - - - 1.3. By solid fire blocking in accordance with Section R602.8.1;
- - - - - 1.4. By protecting both boxes with listed putty pads; or
- - - - - 1.5. By other listed materials and methods.
- - - - 2. Membrane penetrations by listed electrical boxes of any materials provided the boxes have been tested for use in fire-resistance-rated assemblies and are installed in accordance with the instructions included in the listing. The annular space between the wall membrane and the box shall not exceed 1/8 inch (3.1 mm) unless listed otherwise. Such boxes on opposite sides of the wall shall be separated as follows:
- - - - - 2.1. By a horizontal distance of not less than 24 inches (610 mm) except at walls or partitions constructed using parallel rows of studs or staggered studs;
- - - - - 2.2. By solid fire blocking in accordance with Section R602.8;
- - - - - 2.3. By protecting both boxes with listed putty pads; or
- - - - - 2.4. By other listed materials and methods.
- - - - 3. The annular space created by the penetration of a fire sprinkler provided it is covered by a metal escutcheon plate.

An exhaust duct is an example of a "through penetration" as the penetration (the duct) "goes through" the wall assembly.

A receptacle outlet is an example of a "membrane penetration" as it simply penetrates one side of the wall assembly, i.e., one "membrane" of the assembly.

Codeman