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Fireblocking (Firestopping) vs Draft Stopping

2022 0415 Ideas Post
Apr 15, 2022
Ed Feibel

Fireblocking and draft stopping are very similar when described in the code but have different applications and uses in the building and are required to be installed in different areas. It's easy to confuse the two items and where each one is required to be installed. This blog will help to clarify the differences.

Fireblocking is intended to resist the movement of flames, smoke, and gasses in a vertical direction, whereas draft stopping is only intended to resist the passage of smoke and gasses, but not flames, in a horizontal direction. Each element is addressed in separate sections within Chapter 7 of the Chicago Building Code.

Fireblocking Locations

  • Fireblocking is required in any concealed wall spaces, including furring, parallel rows of studs, including vertically at the ceiling and floor levels, and horizontally at all intervals not exceeding 10’-0”.
  • At all connections between concealed horizontal and vertical spaces, such as floor joists or trusses, soffits, cove ceilings, and similar locations

The installation of fireblocking in these areas limits flame and smoke propagation through walls and spaces such as between studs or where the floor or ceiling meets the walls.

  • Between the stair stringers at the top and bottom of each run

This limits the chance of a fire or smoke propagating through the stairs and moving from floor to floor through the concealed spaces below the steps.

  • All ceiling and floor openings around vents, pipes, ducts chimneys, and fireplaces - note that at this location materials are specifically permitted to be “materials tested in form and manner intended for use to demonstrate its ability to remain in place and resist the free passage of flame and the products of combustion”. At these locations it is not required to be the materials noted below

This requirement is commonly seen in high-rise buildings, as there are almost always pipes and ducts passing through the floors, and fireblocking is required around the openings. It is important to note on the drawings the product being used to confirm that a UL-listed or tested fireblocking material is proposed, as that is something that is commonly missed on drawings.

  • Within concealed spaces of combustible exterior wall coverings into areas not exceeding 100 sq. ft, 20’-0” max in either direction with some exceptions

Similar to above, this is to help with limiting flame and smoke propagation through the concealed spaces in exterior walls.

Acceptable Fire Blocking Materials

The acceptable materials for fireblocking are defined in Section 718.2. 

  • “Fireblocking shall be made of 2 nominal lumber
  • Two layers of 1” nominal lumber with broken lap joints
  • One layer of .719” wood structural panels with joints backed by .719” wood structural panels
  • One layer of .719” particleboard with joints backed by .719” particleboard
  • ½” gypsum board
  • ¼” cement-based millboard, or batts of mineral wool, fiber or other approved materials installed securely in place.” 

These materials allow for options in different buildings and construction types for firestopping in different locations. If a project is looking to use any items that are not listed, it should be reviewed with Department of Buildings (DOB) to confirm that they will be acceptable for the applications.

Draftstopping Locations

  • Draftstopping is required within the floor assemblies of buildings that are of any type other than Group R, and are non-sprinklered. The draftstopping must subdivide the area within the floor assembly into horizontal areas not exceeding 1,000 sq. ft.
  • In attics with occupancies other than Group R, draftstopping is required so that the horizontal area does not exceed 3,000 sq. ft. In group R-2 occupancies, draft stopping in attics is required to divide any attic space into areas of 3,000 sq. ft. maximum or above every 2 dwelling units, whichever is smaller.

As noted above, daft stopping is intended to limit smoke movement through concealed spaces. The required locations for it are focused on areas where smoke could move through a building.

Acceptable Draftstopping Materials

The materials for draftstopping are also defined in 718.3.1 and shall be not less than 

  • ½” gypsum board
  • ⅜” wood structural panel
  • ⅜” particleboard
  • 1” nominal lumber, cement fiberboard, batts or blankets of mineral wool, glass fiber, or other approved materials that are adequately supported 

Generally, there are less stringent requirements for draftstopping, as it is only needed to be smoke resistant, rather than flame.

If you have any questions regarding where fire blocking, draftstopping or other fire prevention systems are required, as well as any other building code questions, please reach out to us.