What is Draftstopping and When is it Required? | Solved!

Author : Building Code Trainer

In the world of building safety, draftstopping plays a crucial role yet remains one of the lesser-known aspects of fire protection when it comes to building code compliance. Draftstopping is essential for subdividing spaces within buildings to control the spread of fire and smoke, thus safeguarding lives and property.

In this article we will get into the specific regulations surrounding draftstopping as outlined in Section 718 of the 2021 International Building Code, offering a clear explanation of its materials, requirements, and implementation.

What is Draftstopping?

Draftstopping refers to materials installed within buildings to subdivide concealed spaces, such as those found above ceilings and under floors, to limit the spread of fire and smoke. Unlike firestopping, which focuses on vertical barriers between floors or units, draftstopping targets horizontal separations within concealed combustible compartments.

Definition

Let’s look at the definition for Draftstopping found in Chapter 2 of the IBC:

DRAFTSTOP – A material, device or construction installed to restrict the movement of air within open spaces of concealed areas of building components such as crawl spaces, floor/ceiling assemblies, roof/ceiling assemblies and attics.

When is Draftstopping Required?

Draftstopping is a critical safety measure required in buildings to control the spread of fire, smoke, and gases through large concealed spaces. According to the IBC, draftstopping must be installed specifically in combustible concealed locations within buildings—this includes both floor/ceiling spaces and attic spaces as detailed in Sections 718.3 and 718.4, respectively. The necessity of draftstopping arises from the inherent vulnerability of these spaces where fire can spread rapidly through the paths of least resistance, often exacerbated by voids in construction that not only propagate fire but complicate extinguishing efforts.

The key to understanding when draftstopping is required lies in the term “combustible concealed spaces.” This refers to areas in a building constructed with materials that can burn, unlike in noncombustible construction where such measures are not required. The code mandates that these materials and spaces must adhere strictly to the regulations designed to compartmentalize and thereby limit the movement of fire and its associated dangers.

The implementation of draftstopping is part of a broader strategy to enhance building safety by ensuring that potential fire spread within these hidden voids is adequately controlled, allowing for more effective fire containment and suppression. This section of the code not only prescribes where draftstopping is required but also specifies the acceptable materials to be used, ensuring that what is installed is capable of performing its intended function in the event of a fire.

Draftstopping In Floors

According to Section 718.3, draftstopping must be installed in floor/ceiling assemblies across all types of occupancies, where required by Section 708.4.2. For non-Group R occupancies, it’s required that the area of any concealed combustible floor/ceiling space does not exceed 1,000 square feet.

Exception

An exception to this rule applies to buildings equipped with a comprehensive automatic sprinkler system, which may omit the need for draftstopping if the sprinklers are compliant with Section 903.3.1.1 of the Code.

But what about Section 708.4.2, what does that say? This section is under “Fire Partitions” and it mentions that in combustible construction where fire partitions do not extend to the underside of the floor or roof sheathing, then the hollow vertical space above and along the line of the fire partition shall be provided with either fire blocking or draftstopping.

There are some exceptions to this as well which can be found in Section 708.4.2.

Draftstopping In Attics

Draftstopping in attics, according to Section 718.4, must also be installed when required by Section 708.4.2. In non-Group R occupancies, the subdivided spaces of combustible attic and concealed roof areas must not exceed 3,000 square feet. However, it is crucial that these subdivided spaces maintain proper ventilation according to Section 1202.2.1 to prevent moisture-related issues and ensure temperature control.

Exception

Similar to floors, buildings that are fully equipped with automatic sprinkler systems are exempt from this requirement if the sprinklers are compliant with Section 903.3.1.1 of the Code.

Materials Used in Draftstopping

Selecting the correct materials for draftstopping is crucial. Section 718.3.1 of the code specifies a range of materials that can be used to effectively prevent the spread of smoke and gases through large concealed spaces in buildings. This selection is critical because the materials must not only fit the structural requirements but also withstand the conditions of a fire at its initial stages. The code specifies the following materials:

1. Gypsum Board: At least 1/2-inch thick, gypsum board is a common choice due to its fire-resistant properties.
2. Wood Structural Panels and Particleboard: These must be at least 3/8-inch thick. These panels offer a solid barrier and are often used due to their availability and ease of installation.
3. Nominal Lumber: 1-inch nominal lumber is also on the list of approved materials, providing a robust physical barrier to the spread of fire and smoke.
4. Cement Fiberboard: This material is noted for its excellent fire resistance and durability, making it an ideal choice for draftstopping.
5. Mineral Wool and Glass Fiber Batts or Blankets: These materials are effective in blocking smoke and gases and must be compressed to fill the voids completely, ensuring no gaps are left that could allow the passage of smoke or flames.

It is essential to ensure that the draftstops remain in place and functional when exposed to the heat and the dynamics of a fire. The integrity of the draftstops must be maintained, meaning they should not collapse, fall out of place, or degrade in a way that would allow fire, smoke, or gases to bypass them.

While the materials listed are specifically approved for use in draftstopping, the code also allows for the use of other materials, provided they are supported adequately and meet the safety standards necessary to withstand initial fire exposure. This flexibility ensures that building professionals can choose the best materials available for the specific requirements of each building project.

The materials typically used in fireblocking can also be appropriate for draftstopping, indicating a crossover in the applications of these safety features within concealed spaces. It’s important to note that while materials like mineral wool and glass fiber batts are excellent for draftstopping, they must be used differently from their application in insulation, where compression is to be avoided. In draftstopping, these batts need to be compressed to ensure no spaces are left uncovered.

Draftstop Protection for Attic Access Openings

Section 718.4.1.1 requires the openings in draftstopped attic spaces be protected. These openings, that are required for attic access as per Section 1209.2, must be constructed using materials that at least match the draftstopping material itself and are equipped with self-closing doors that feature automatic latches.

This setup ensures that the draftstop’s functionality is immediately restored after access, thereby maintaining continuous protection against the spread of fire and smoke.

Fire personal may need to gain access to all spaces of an attic therefore when draftstops are provided, this section of code allows for opening within these spaces as long as they adhere to section 718.4.1.1.

Final Thoughts

Draftstopping is essential for minimizing the risk of fire and smoke spread within buildings. By following these specific guidelines laid out in the 2021 International Building Code, construction professionals can ensure that buildings are not only safer but also compliant with critical safety regulations.

Staying updated with these codes are crucial for anyone involved in building design and construction.

For more information regarding draftstopping requirements, be sure to check out Section 718 of the 2021 International Building Code.

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