An introduction to fireblock and firestop sealant systems.

A concrete wall floor assembly being inserted into the furnace.

Firestop and fireblock sealants have two commonalities: they both contain the word “fire” and are both an integral part of life safety. When a fire occurs, smoke and fire can spread quickly. The amount of time it takes to spread depends on structural openings, which feed the fire with oxygen and allow it to travel from room to room and floor to floor. Firestop or fireblock sealants allow responders to rescue occupants and extinguish the fire with the least amount of damage.

A structure is made up of floors, walls and ceilings. At intersections where they meet, there are voids or joints. Filling joints with a firestop or fireblock sealant will help create a “compartment.” In one-room structures, the fire will be sealed within the room - no outside air will fuel the fire and there are no joints for the fire to escape until the walls, floor, and ceiling are compromised. In the case of multiple-room structures, the goal is compartmentalization - to contain the fire in the room in which it originated for as long as possible.

After the floors, walls and ceilings are constructed, pipes, wires, cables, ducts, and other components can be installed. Unfortunately, when a hole is cut it is not the exact size of the penetrating item to be installed, which results in an annular space. This space, which can give a fire momentum, must be filled. A firestop or fireblock sealant can be used to prevent the passage of flame and smoke. It can also restrict the flow of oxygen from one compartment to the next.

A look inside the furnace while a test is being performed.

Fireblock Sealant

Fireblock sealants are for use in one- and two-family dwellings and are covered in the International Residential Code (IRC):

Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space. Fireblocking shall be provided in wood-frame construction in concealed spaces of stud walls and partitions; vertically at the ceiling and floor levels; and horizontally at intervals not exceeding 10 feet. Install fireblocking at openings around vents, pipes, ducts, cables, and wires at ceiling and floor level with an approved material to resist the free passage of flame and products of combustion.

Over the years, the definition of a fireblock has evolved in the IRC. Originally, a fireblock was defined as a non-combustible sealant that was tested to and passed ASTM E 136, “Standard Test Method for Behavior of Materials in a Vertical Tube Furnace at 750°C.” This definition has since changed; no longer is compliance with ASTM E 136 a requirement.

Choosing the right fireblock sealant can be confusing. The Authority Having Jurisdiction (AHJ) that inspects the proper installation of the fireblock sealant may use one of many building codes. The regional building codes used in the past are being replaced with the IRC. But, depending on the AHJ, any one of many building codes could be used. If the AHJ references the IRC, the proper fireblock sealant can vary, depending on what year’s version of the IRC is being used.

Hose stream test.

Installation and Inspection of Fireblock Sealants

Installing a fireblock sealant and receiving approval from a local inspector can be tricky. A contractor can install fireblock sealants in a home and receive an approval by a local inspector, then install the same sealant in a location five miles away and fail inspection.

In addition, some inspectors allow the use of expanding foams for fireblocking. Contractors appreciate the labor savings of these foams - a quick push of the finger and the annular space is sealed. However, many inspectors will not allow the use of foam because it burns so quickly and expels toxic gases in the event of a fire. Even if the inspector is using a code that does not require the use of a non-combustible fireblocking, he or she may not allow it to be used. What’s more, some inspectors require that the fireblocking material be red in color, even though there are non-combustible fireblock sealants in other colors.

The more knowledgeable the inspector is in the codes and what to look for in a fireblock sealant, the easier it is on the contractor applying the material. The contractor’s know-how is also an important factor; familiarity with the codes and the local inspector’s fireblock requirement is a must. While there are many different codes, there is one constant throughout all jurisdictions: Application of a non-combustible fireblock sealant will always be approved if installed properly. Proper installation means completely sealing the opening.

Firestop sealant applied to penetration.

Firestop Sealant

There are three key elements to life safety: detection (fire and smoke alarms to warn of the problem); suppression (sprinklers, fire extinguishers, etc., to help keep the fire at bay); and compartmentalization (to keep the fire isolated, as described previously). Detection alone is obviously not a good option; in a high-rise building, detection without suppression and compartmentalization may result in lives lost. Suppression alone means that the fire can travel within walls and floors very quickly - two places where sprinklers are ineffective. In addition, improper maintenance of a sprinkler system can render it useless. If the building is compartmentalized, occupants may have time to safely evacuate in the event other systems malfunction. Even if properly working sprinklers suppress the fire, the building will still be full of smoke. Smoke inhalation is the cause of 75% of fire-related deaths. If the building is properly compartmentalized, the smoke will be isolated, providing occupants with more time to escape safely.

Firestopping is also known as passive fire protection - the sealing and compartmentalizing of rooms between fire-rated walls, floors, and ceilings. These fire-rated assemblies are found in commercial construction. Fireblock sealants are used in non-fire-rated walls, floors and ceilings. Remember that they are used in Type V combustible construction, which is commonly found in residential construction. A fireblock sealant is used alone to seal openings. A firestop sealant is used in conjunction with other building materials as a tested system.

Application of firestop sealant.

Firestop Codes and Testing

Firestopping is addressed in the National Building Code (NBC), Uniform Building Code (UBC), Standard Building Code (SBC), NFPA 101 Life Safety Code, NFPA 70 National Electrical Code, Uniform Plumbing Code (UPC) and the International Building Code (IBC). The IBC states:

Through penetrations shall be protected by an approved penetration firestop system installed as tested in accordance with ASTM E 814/UL 1479 (Standard Test Method for Fire Tests of Through Penetration Firestops). An F-Rating of not less than the required fire resistance rating of the wall penetrated. An F-Rating and T-Rating of not less than the required rating of the floor penetrated. Joints installed in or between fire resistant rated assemblies shall be protected by an approved fire resistant joint system designed to resist the passage of fire for a time period not less than the required fire resistance rating of the assembly in which it is installed. Fire resistance joint systems shall be tested in accordance with the requirements of ASTM E 1966/U.L. 2079 (Standard Test Method for Fire Resistance of Building Joint Systems).

Unlike fireblock codes, firestop codes are very specific and have no room for interpretation by the AHJ. Walls, floors or ceilings in a building are tested in a fire for 1, 2, 3 and 4 hours per ASTM E 119/UL 263 (Standard Test Method for Fire Tests of Building Construction and Materials) and thus rated for 1, 2, 3, or 4 hours. These tests are performed by the following third-party testing laboratories: Underwriter Laboratories Inc. (UL); FM Global (Factory Mutual); Intertek (Warnock Hersey, Omega Point Laboratories); and Southwest Research Institute. These labs test to American Society of Testing Materials (ASTM) and Underwriter Laboratories Inc.

There are three parts to a firestop system: a fire-rated wall, floor or ceiling; a penetrating item; and the firestop fill material. The testing of the system consists of duplicating the construction of the wall or floor; cutting holes and installing penetrating items; and filling the annular space with firestop sealant. In many cases, mineral wool or a backer rod is also part of the firestop fill material. After the wall or floor is constructed, the dimensions of all components are recorded: the thickness and material (concrete, wood joists, gypsum board) of the wall or floor; the size of the penetrating item (such as 2” PVC pipe, 4” copper pipe, 24” x 24” duct, or 2” x 2” bundles of wires or cable); the size of the hole cut for the penetrating item; the annular space remaining, which is filled with firestop sealant; and the thickness of the mineral wool or size of the backer rod in the annular space and the thickness of the firestop sealant applied.

This duplicate assembly is then placed in a furnace and burned for 1, 2, 3 or 4 hours at temperatures from 1,600°F for one hour up to 2,000°F for four hours. At the end of the burn, the floor or wall is removed from the furnace, stood on its side and subjected to a hose stream of 30 psi. The amount of time exposed to the hose stream depends on the size of the assembly. If the unexposed side of the penetration or opening is intact with no water or holes observed after the hose stream test, that assembly has passed.

During the test, the following fire-resistance ratings are recorded.
  • F-Rating - The time period that the firestop system resisted the spread of flame through the penetration or opening. If the assembly was tested for two hours and no flame spread out of the furnace through the penetration, a two-hour F-Rating has been achieved.
  • T-Rating - The time period that the firestop system resists the passage of flame through the penetration or opening and limits the maximum temperature rise on the unexposed side to less that 325°F above ambient temperature. If the assembly was tested for two hours, but the penetrating item temperature rose 325°F above ambient temperature after one hour, a one-hour T-Rating has been achieved.
  • L-Rating - The time period that the firestop system limits the spread of smoke through the penetration or opening.
This data is written up into a “system” if the tested assembly was successful. The system is proof that the particular assembly, with all the specific penetrating item dimensions and firestop fill material thicknesses, passed the test for 1, 2, 3, or 4 hours. Keep in mind that there are thousands of tested systems to cover all of the possible combinations of wall, floor, and ceiling assemblies, as well as various diameters and types of pipes, cables, wires, and ducts. This testing is necessary to ensure that if a building is constructed of two-hour fire-rated assemblies and the assemblies have been compromised by the additions of penetrating items, those assemblies will be brought back up to a two-hour rating.

Installation and Inspection of Firestop Sealants

Firestop sealant installers should ensure that the sealant they are using has been tested to the systems in which it will be installed. The system should be installed exactly as written up - which is how it was tested. In addition, installers must be aware of the F and T Rating required for that construction.

After installation, an AHJ will visit the job site for an inspection. The installer presents the inspector with the systems that were installed and the inspector ensures that all assemblies and penetrating item dimensions match up. He or she will randomly disassemble a system to ensure the correct amount of mineral wool or backer rod has been used and the correct depth of firestop sealant has been applied.

The knowledge level of firestop sealant installers varies. Individual tradespeople (such as plumbers, electricians, HVAC, etc.) may perform the installation; in many cases, these installers are given a caulk gun and a case of firestop sealant and are told to seal around all the holes. Sealing around the holes, however, is generally not the same as installing a system. An improperly trained inspector may look at this type of installation, see red sealant applied, and approve the installation. However, this is not the intent of the codes and will not properly compartmentalize a building.

Fortunately, there are firestop contractors available with professionally trained installers. The Firestop Contractors International Association (FCIA) has members throughout the world that can perform the proper installation of a firestop system. A list of contractors can be found on In addition, Underwriters Laboratories Inc. ( and FM Global ( have firestop contractor programs available to ensure proper training.

An inspection by a properly trained and knowledgeable AHJ will enforce codes and ensure the proper installation of firestop systems. The International Firestop Council (IFC), a not-for-profit association of manufacturers, distributors and installers of passive fire-protection materials and systems, offers free training seminars for inspectors throughout North America.

For more information about firestop materials and the IFC, visit