Key changes in NBC 2020: New code requirements for joint firestopping

by tanya_martins_2 | October 16, 2024 9:50 am

By John Valiulis

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The National Building Code of Canada (NBC) requires some walls and floors in a building to have a fire-resistance rating. Those rated assemblies are termed “fire separations.” They prevent fire and smoke from spreading prematurely to adjacent areas above or near the point of fire origin, allowing for safer evacuation from the building and a relatively safer fireground for firefighters.

There is no quick or easy way to describe which floors and walls will require a fire-resistance rating in the various buildings that could be built. The need for such separations is assigned over dozens of pages in the code as a function of the building height, building area, occupancy of the building (or parts of the building), and whether the building includes automatic fire sprinkler protection. One common requirement for fire separations is between dwelling units in a multi-unit residential building and between dwelling units and public corridors.

However, once a fire separation is mandated, it should not be compromised by gaps that could allow fire or smoke to spread through or around the rated floor or wall. This is why the code requires fire separations to have suitable opening protectives (e.g. rated doors and windows), fire and/or smoke dampers for air ducts penetrating the fire separation (depending on many variables), firestopping of penetrations, and firestop systems for joints within or between the rated assemblies.

The presence of joints between rated assemblies is inevitable. Some joints will exist due simply to construction tolerances. No matter how carefully they have been built, it is nearly impossible to have a true zero gap that is fire- and smoke-tight between adjacent assemblies of different construction.

Some joints allow relative movement of the adjacent assemblies, such as the top of wall joints, when walls are non-loadbearing.

What did the NBC require previously? Answer: “Continuity”

The 2015 and previous editions of the NBC 
dealt with the protection of joints with the following requirements:

3.1.8.3 Continuity of Fire Separations

4) The continuity of a fire separation shall be maintained where it abuts another fire separation, a floor, a ceiling, a roof, or an exterior wall assembly. (See Note A-3.1.8.3.(4).)

A-3.1.8.3.(4) Fire Separation Continuity. The continuity of a fire separation where it abuts against another fire separation, a floor, a ceiling or an exterior wall assembly is maintained by filling all openings at the juncture of the assemblies with a material that will ensure the integrity of the fire separation at that location.

To summarize and explain, the code mandated that wherever a discontinuity existed, such as where it typically occurs for joints, the fire rating of the underlying assembly should be carried through that juncture. For example, in a one-hour rated floor assembly, the code would have required the joint between that floor and any other adjacent assembly to have a one-hour fire rating.

To help explain what the code was trying to accomplish with the continuity requirement, the NBC provides “Objectives” in division A, part two, of the code, and in “Functional Statements” in division A, part three. Those are, as follows, for code article 3.1.8.3.(4) that deals with continuity, with OS1 for the protection of people, and OP1 for the protection of the building itself:

OS1 Fire Safety

An objective of this Code is to limit the probability that, as a result of the design or construction of the building, a person in or adjacent to the building will be exposed to an unacceptable risk of injury due to fire. The risks of injury due to fire addressed in this Code are those caused by—OS1.2 – fire or explosion impacting areas beyond its point of origin.

OP1 Fire Protection of the Building

An objective of this Code is to limit the probability that, as a result of its design or construction, the building will be exposed to an unacceptable risk of damage due to fire. The risks of damage due to fire addressed in this Code are those caused by—OP1.2 – fire or explosion impacting areas beyond its point of origin.

Functional statement: “F03 To retard the effects of fire on areas beyond its point of origin.” The intent of the code requirement for continuity of fire separations is to prevent fire movement beyond “its point of origin” successfully.

Up through the 2015 NBC, the code never specified how the designer and contractor were supposed to ensure “continuity” of fire resistance was provided at the junctures.

The third edition of Canadian fire test standard CAN/ULC-S115, Standard Method of Fire Tests of Firestop Systems, published July 2005, established the fire test method that allowed joint firestop systems to be tested and listed by ULC. The first listings appeared the very next month. Design and construction professionals and authorities having jurisdiction (AHJs) have apparently been increasingly aware of the test standard and available listings. However, the test method was unmentioned in the code through its 2015 edition. Nevertheless, it seems that in recent years, most buildings with required fire separation walls or floors have been fitted with joint systems tested and listed to CAN/ULC-S115. This would then satisfy the code requirement (despite being vague) and provide the code-expected level of fire safety.

2020 code evolution

Although many people feel code revisions create new requirements, the opposite is often true—building code revisions merely codify the best practices that are already broadly adopted. This latter situation seems to have been the case with NBC 2020’s handling of joint firestopping.

The 2020 NBC now provides the following revised and improved requirements for the continuity of fire separations:

3.1.8.3. Continuity of Fire Separations

2) Except as provided in Sentence (5), the continuity of a fire separation having a fire-resistance rating that abuts another fire separation, a floor, a ceiling, or a roof shall be maintained by a firestop conforming to Sentence (3). (See Note A-3.1.8.3.(2).)

3) The firestop required in Sentence (2) shall have an FT rating not less than the fire-resistance rating of the abutting fire separation when subjected to the fire test method in CAN/ULC-S115, “Standard Method of Fire Tests of  Firestop Systems.”

The key concept in the code is that joints between a fire separation and an adjacent assembly must now have a fire rating based on a specific fire test, CAN/ULC-S115. One cannot guess or hope that a specified joint seal will provide the needed continuity of the fire separation’s fire resistance rating. One must now find a listed joint firestop system that precisely matches the field conditions.

The fire rating of joint firestops is expressed as an “FT” rating. An FT rating provides the dual performance of preventing the spread of fire (F) and preventing an excessive temperature (T) rise on the non-fire side that could otherwise ignite combustibles. The detailed pass/fail criteria are defined in the test method.

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Figure 1 (page 8) shows the setup of the thermocouples (TC) on the unexposed side of a head-of-wall joint firestop system ready for testing, which in this case is a joint between a gypsum board wall and a mass timber floor assembly. The TCs measure the temperature at the wall assembly, floor assembly, and joint seal. The actual TCs are not pictured, as they are under ceramic fibre pads (light brown in the image), as required by the test standard. The time to failure, which is the temperature rising above 181 C 
(358 F), determines the FT rating.

The code now specifies that the joint firestop FT rating (e.g. one hour, two hours) must equal the fire-resistance rating of the fire separation.

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Searching for joint firestop systems

The broadly accepted past practice of needing to find a tested joint firestop system is now mandatory. Some construction industry professionals might not know yet where to look for these firestop system listings. The most user-friendly way to search for and select joint firestop systems is to use the online system selectors from the major firestop manufacturers. Those online search tools allow searches based on various useful criteria.

To look at multiple firestop manufacturers, refer to the UL/ULC online directory, UL Product iQ. Unfortunately, it does not yet provide in-depth search capabilities using all the field condition criteria the manufacturers account for in their online system selectors.

UL’s overall online listings directory uses Category Control Numbers (CCN). The CCN for “Joint Systems Certified for Canada” is XHBN7. This is useful when using UL Product iQ to search for solutions. This category currently includes more than 1,900 joint firestop system listings for Canada.

Intertek is a testing and listing laboratory that also provides listings to CAN/ULC-S115. However, when using Intertek, one always needs to verify what edition of CAN/ULC-S115 a listing is based on, as it still lists (publishes) some previously tested systems after a test standard changes. Changes to test standards commonly make some previous listings noncompliant with the latest test standard edition. There is no note when a system listing may not or does not comply with the current test standard. The current edition of CAN/ULC-S115 is the fifth edition, published in 2018. A small revision was also made in 2023 relevant to curtain wall edge-of-slab joint testing.

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Joints will move

Joints between adjacent assemblies will very often be dynamic joints, meaning they can or will experience some degree of relative movement over the life of a building. The joint with the most obvious need to accommodate movement would be the top-of-wall (TOW) joint for non-loadbearing walls since the floor above will deflect up and down to some extent due to dead and live loads. In addition, the floor below a given wall will also deflect under varying loads, creating movement in the TOW joint 
as the entire floor and wall flex downwards 
and upwards.

Those floor deflections are usually imperceptible to occupants. However, if a static joint firestop system is used in dynamic joints, the result could be the static joint system failing and allowing passage of fire and/or smoke past the fire separation.

The need for the joint firestopping to accommodate movement has been indicated even in previous editions of the NBC; here is an example from NBC 2015:

A-3.1.8.1.(1)(b) Continuity – General Requirements

When choosing products for firestopping, the physical characteristics of the material used at the joints as well as the nature of the assembly and its potential movement should be taken into consideration.

The annex to NBC 2020 goes into greater depth and detail to describe this. Extracted from A-3.1.8.3.(2) Fire Separation Continuity:

Fire-resistance-rated joint firestop systems can be tested and listed as either static or dynamic. Dynamic joint firestop systems are subjected to movement cycling prior to undergoing fire testing at maximum joint extension. This approach ensures that the fire-resistance rating of the joint firestop system will be maintained even after the joint has cycled through its anticipated range of movement over the service life of the building. Most joints between fire-resistance-rated assemblies, other than those between loadbearing elements, experience some movement over the service life of the building.

The joint firestop systems listed by UL have a system naming nomenclature that describes the primary category of each listed joint system. Dynamic joint systems, tested and demonstrated to accommodate movement, will have the letter “D” in the joint system number, such as “HW-D-0758” (“HW” refers to the head-of-wall joint).

• 
Most listed wall-to-wall and wall-to-column joint firestop systems are static (letter “S”) joint firestop systems. Bottom-of-wall joint firestop system listings are all static.
• 
Other categories of joint system types are mostly dynamic system listings, although some are static.

A dynamic joint system will be cycled over its intended range of movement before the fire test to establish the per cent extension and per cent compression in the joint system listing. The test sponsor will decide what movement to use in the cycling test, typically expressed as per cent of the nominal joint size. Manufacturers generally have information and data regarding the movement capabilities of their various sealants and devices. The CAN/ULC-S115 test standard for dynamic joint firestop systems requires 500 movement cycles at a minimum cycling rate of 10 movement cycles per minute.

After the cycling, the test specimen is moved to the maximum joint extension and allowed to stabilize. Within 96 hours of completing the cycling test, it is then fire-tested at maximum extension. The fire test determines the joint firestop system’s FT rating. The listing will report the per cent movement that was proven during the cycling test.

When a given joint application is recognized to require a dynamic joint firestop system, it is insufficient to choose a system listed as dynamic without also looking at the movement allowance stated in the listing. One must find a system that provides a sufficient degree of movement. Allowable movement in UL-listed systems is usually reported as a per cent of the nominal joint width.

For example, for a 30-mm (1.18-in.) head-of-wall joint and a 12.5 per cent listed compression and extension for the firestop system (a common movement limit for “stuff and spray” joints), the allowable movement would be only 3.8 mm (0.14 in.) up or down. As a practical matter, most designers of heavily compartmented interior spaces aim for a deflection at mid-span of 12 to 13 mm (0.47 to 0.51 in.), or L/480, whichever is less. In this example, the 30 mm (1.18 in.) joint firestop system would need to be closer to 40 per cent movement. Either the joint needs to be increased in size so the 12.5 per cent joint firestop movement would suffice, or a different type of joint firestop system needs to be selected with at least 40 per cent movement.

Joint firestops have the following common maximum movement capabilities based on the general category of joint firestopping used:

• 
100 per cent compression or extension for mechanical joint systems
• 
50–100 per cent compression or extension for preformed joint firestop products
• 
< 20 per cent compression and extension for elastomeric joint sealants (commonly 13 to 
16 mm [0.51 to 0.23 in.] depth of sealant)
• 
< 15 per cent compression and extension for elastomeric joint sprays over compressed mineral wool forming material (commonly 
3.2 mm [0.12 in.] wet thickness)

The bullet points mention “performed joint firestop products.” Preformed joint firestop products, as they pertain to head-of-wall firestopping, should be investigated further if one is not yet familiar with this growing trend in joint firestopping. These products are at the leading edge of joint firestopping evolution. This general category includes joint firestop solutions that are primarily “prefab.” They are faster to install and do not depend on an installer to assemble raw materials on a job site, as would be the case with caulked or sprayed joints firestops. This is ideal in an era of increasing labour costs and shortages. The number and variety of such products offered by firestop manufacturers have increased tremendously over the past decade. Interior finishing contractors can install most of these products while constructing a wall, 
and some options allow installation after a wall 
is constructed.

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Figures 4 (page 14) and 5 show an example of a preformed joint firestop product that will accommodate movement for a dynamic TOW joint. Many such firestopping products are installed together with and at the same time as the top track. In Figure 5, the conduit penetrations through the wall must be provided with penetration firestops tested to CAN/ULC-S115.

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Compared to the caulked or sprayed joint firestopping systems used in previous decades, preformed joint firestop products are easier to install consistently, with minimal training, with some options being nearly fool-proof. This is an advantage of firestop inspections getting more thorough in many jurisdictions. Figure 6 (page 18) shows the results of a poorly executed attempt at joint firestopping. This helps illustrate the desire and industry movement towards the preformed joint products.

Another “buyer beware” point when looking for a dynamic joint system is the existence of listed joint systems that indicate in the listing header the movement is for “compression-only.” A dynamic joint is one that will move in both directions (compression and extension) over the life of a building. Theoretically, the only TOW joint that would be compressed and could 
never expand beyond its initial installation joint width would be the TOW joint for a wall in the lowest-level basement. The more useful joint firestop systems will allow compression and extension movement.

Some listed systems report a different per cent value for compression than extension. The reported joint capability for extension is sometimes significantly less than for compression. Many firestop materials tend to handle compression more easily than extension, as they may tear if extended beyond their inherent capability or result in a lower FT rating if the extension is equivalent to compression. Verify the listed per cent extension is sufficient for the specific joint where the system is intended to be installed.

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Are joint firestops always needed?

The only exception provided to the broad code requirement for tested joint firestop systems is in sentence (5) of 3.1.8.3, for joints within/between gypsum boards, “where such joints consist of gypsum board that is attached to framing members and arranged to restrict the passage of flame and smoke through the joints.”

This is a recognition of the way construction takes place today. Joints between adjacent gypsum boards, whether straight (in-plane) or at an angle, have always been “mud and taped.” For fire-resistance-rated assemblies, gypsum boards must be butted against each other, as mandated by the listings for those assemblies. The Gypsum Association describes the acceptable tolerance as follows: “Joints between boards in fire-rated assemblies must be in “moderate contact,” meaning that the gypsum boards should be touching and gaps minimal.”

For example, suppose a measurable gap is needed between gypsum boards in a rated assembly for control joints within a rated wall. In that case, joint firestops tested and listed to CAN/ULC-S115 are available to fill the need.

Conclusion

NBC 2020 has unambiguous requirements for joints firestopping at fire separations. It requires systems tested to CAN/ULC-S115, with an FT rating equal to the fire-resistance rating of the abutting assembly. The anticipated movement of each joint must be accommodated in selecting the correct system from the 1,900 UL-listed joint firestop systems for Canada.

To mention an additional joint firestop consideration not discussed, some walls are required by code to provide a given Sound Transmission Class (STC) rating to protect from airborne noise transmission. One example is the common walls in multi-residential occupancies. Different joint firestop system types will have significantly different abilities to maintain (and not degrade) the STC rating of the specified wall assembly. Those acoustical capabilities will not be reported in UL firestop listings. One must consult with manufacturers’ published acoustical test reports.

Author

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John Valiulis is the director of codes and standards with Hilti North America. He has 39 years of experience working in multiple countries as a fire protection engineer in research, construction applications, and national codes and standards development. He holds degrees in chemical engineering and fire protection engineering. Valiulis has instructed fire protection engineering seminars in North America, South America, Europe, Asia, the Middle East, and the Caribbean and has written for many U.S. and Canadian publications. He has served on six NFPA technical committees and numerous ASTM committees. He has contributed to the development of the National Building Code of Canada (NBC) and the International Building Code (IBC). Valiulis can be reached at john.valiulis@hilti.com.

Source URL: https://www.constructioncanada.net/key-changes-in-nbc-2020-new-code-requirements-for-joint-firestopping/

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