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Clarifying the Difference Between Fireblock and Firestop1

Until recently, most of the United States used the term "firestopping" interchangeably with "fireblocking" or "draftstopping" when describing two different construction objectives. However, it is important to understand the significant difference between a "Fireblock" and a "Firestop".

The practice of protecting penetrations that pass through a fire-rated assembly from one compartment to another was, and still is, referred to in the construction industry as "Firestopping". From the mid 1980's on, protecting through-penetrations (firestopping) has evolved into a performance-oriented discipline, which was reflected in the building codes through the adoption of test method ASTM E-814, the "Test Method for Fire Tests of Through-Penetration Fire Stops".

On the other hand, protecting against the possible spread of fire within the cavities or concealed draft openings in wood frame construction has been addressed in the codes by subdividing large concealed spaces and smaller spaces inside the stud walls, at soffits and drop ceilings and at the top and bottom of stair stringers, etc. with "fireblocking" and "draftstopping". Unfortunately, confusion has existed due to vague code language, and to the misuse of the term "firestop" to describe different construction practices. Firestopping and fireblocking are still essentially the same in some people's minds. But they are clearly different. Fortunately, changes were made in the building codes to help clarify the intent and meaning and to distinguish one practice from another.

"Fireblocking" is now defined as generic materials, such as lumber, structural wood panels, gypsum board, cement fiberboard, or particleboard, batts or blankets of glass or mineral wool installed within concealed spaces to resist, or block, the migration of fire and hot gases for an undetermined period of time. Fireblocking is used to subdivide or block off the stud cavity inside a wall, in a soffit over cabinets, and between stair stringers at the top and bottom of a run.

Historically, the term "noncombustible" has been used. Reason would dictate, however, that in combustible construction it is not logical to require noncombustible fireblocking materials on items that do not transfer heat, such as plastic DWV plumbing pipe that penetrates a wood top plate drilled to provide a tight fit. Consequently, the current International Building Code (IBC) and International Residential Code (IRC) both have eliminated the "noncombustible" requirements pertaining to fireblocks and are revised to read "approved material to resist the free passage of flame and the products of combustion". The authority having jurisdiction may determine that the narrowest interpretation of the word "noncombustible" (as in accordance with ASTM E-136) may not be necessary at every location.

Fomo Products, Inc. has worked closely with the International Code Council and third party independent fire testing labs in order to evaluate and approve the use of Handi-Foam Fireblock One-Component Foam for specific fireblock applications. Only those foam manufacturers that carry an ICC-ES evaluation report assuring that the product has been evaluated by the International Code Council should be considered as a suitable fireblocking material.

1 Source: V.J. Lovell, "An Overview of Firestopping and Fireblocking: What's the Difference?", 2001.

This information is provided as a service, and is not necessarily meant to reflect any recommendation, guideline or position of Fomo Products, Inc. Each individual user must determine product suitability for any particular purpose.


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