Much has been written in recent years regarding the importance of having a balanced design for fire protection that involves detection, suppression and containment....
Much has been written in recent years regarding the importance of having a balanced design for fire protection that involves detection, suppression and containment.
As part of a properly constructed containment system, firestop assemblies play an important role in ensuring that fire rated separations are able to perform as originally designed. This article identifies areas in the National Building Code of Canada and typical project specifications as they relate to firestop systems where there are limitations and areas for discussion in how the provisions are applied.
Firestop systems protect against the passage of fire, hot gases and toxic smoke through openings in walls, floors and floor/ceiling assemblies. They could apply to through-penetrations, membrane penetrations, joints, blank openings, gaps and voids.
BUILDING CODE AMBIGUITIES
There are at least two instances where provisions for firestops may not be adequately covered in Canada’s National Building Code (NBC).
The first case involves interpretation of a particular statement. Under section 184.108.40.206, Firestopping of Service Penetrations, the code states: “…building services that penetrate a membrane forming part of an assembly required to have a fire-resistance rating, or a fire separation, shall be either tightly fitted or sealed by a fire stop system that, when subjected to the fire test method in CAN4-S115-M, ‘Standard Method of Fire Test of Firestop Systems,’ has an F rating not less than the fire-protection rating required for closures in the fire separation [Ref: 220.127.116.11.(1) of NBCC 1995].”
This either/or statement could be taken to mean that both methods described will provide an equal, or adequate, level of protection for an assembly in a fire. But what constitutes “tightly fitted” is often misunderstood and has been much debated.
To recent correspondence requesting clarification of “tightly fitted,” the Canadian Codes Centre, which is part of the National Research Council of Canada, responded as follows:
“The clause is going to be changed in the 2005 edition of the NBC to require the penetrating service to be ‘cast in place.’ The other option of sealing by a firestop system will remain.
“The intent of the current (in the 1995 edition of the NBC) requirement of ‘tightly fitted’ has been that there be no gaps around the whole perimeter of the penetrating item, which in practice is difficult to achieve without using a pliable material like mortar or a firestop sealant.
“The views expressed in this letter are those of the staff of the Canadian Codes Centre of the Institute for Research in Construction who assist the Committees which are responsible for the preparation of the National Building Code. These views should not be considered as official interpretations of legislated requirements based on the National Building Code of Canada because the final responsibility for an official interpretation rests with the authority having jurisdiction.”1
Given the above position statement from the Canadian Codes Centre and with the expected upcoming changes to the 2005 NBC, it is reasonable to expect that the intent of “tightly fitted” is met when the penetrating item is cast into the assembly which it is passing through.
Perimeter Construction Joints
Section 18.104.22.168 of Canada’s National Building Code requires that any wall, partition or floor assembly required to be a fire separation shall be constructed as a continuous element. Appendix A provides additional clarification. It states that the continuity of a fire separation at the point where it abuts against another fire separation, floor, ceiling or 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. Essentially, this integrity is what a joint firestop system is expected to provide.
Unfortunately, the issue that needs to be addressed is how to deal with the gap created with the intersection of a rated floor assembly with a non-rated exterior wall assembly. Firestop joint fire testing per CAN4-S115-M (CAN4/ULC-S115-M Standard Method of Fire Tests for Firestop Systems) always involves the intersection between two fire-resistance rated assemblies. A listed system for a perimeter joint system in compliance with CAN4-S115-M therefore is not possible.
In the U.S. a specific ASTM test is available to evaluate exactly the above condition, looking at building perimeter joint systems where the curtain wall is not rated. Issued in 2004, ASTM standard E2307-04 is called: “Standard Test Method For Determining Fire Resistance of Perimeter Fire Barrier Systems Using Intermediate-Scale Multi-Storey Test Apparatus.” The standard was developed to measure the ability of the perimeter fire barrier system to prevent interior fire spread during the deflection and deformation of the exterior wall; the deflection and deformations would be caused by fire exposure both from below and from the outdoor side of the curtain wall. The latter fire exposure test simulates flames licking up the side of the building and stressing the wall panels. Perimeter fire containment systems must be able to withstand both exposures. This standard is expected to be included in the 2006 edition of the International Building Code (IBC).
With over 200 systems already tested and listed for this specific application, the design community should find it easy to be able to comply convincingly with the building code requirement in 22.214.171.124.
PROJECT SPECIFICATION AMBIGUITIES
Provisions in project specifications for firestops can be misunderstood and overlooked, resulting in the misuse of firestop products and systems.
Perimeter Joint Systems
As discussed above, the National Building Code of Canada does not address the issue of firestopping perimeter joint systems between non-rated exterior walls and rated floors in any detail, other than to state the general performance requirement that the integrity of the fire separation must be maintained at the perimeter joint. This lack of building code specificity is reflected in a lack of detail in Division 07270/07840 specifications.
There are solutions available to deal with this shortcoming in a project specification. The easiest and most logical would be to include a reference to ASTM E2307-04, the only existing test standard which specifically addresses the perimeter joint issue.
Another option is to specify the acceptance of “Engineering Judgments” for this firestop configuration. Engineering judgments are created to address construction configurations that fall outside the envelope of tested systems, since such conditions often cannot be redesigned and must not be ignored. These recommendations are not based upon actual fire testing of the design in question, so it is important that engineering judgments be developed in accord with sound engineering principles to help ensure that life safety and structural integrity concerns are not compromised. The International Firestop Council publishes a document on the evaluation of engineering judgments against which a manufacturer’s submitted judgments can be scrutinized.2
Firestopping is typically covered in section 07270 or 07840 of a project’s master specification.
Usually, somewhere in the firestop section there are references to the test standards that the firestop assemblies must be subjected to. As mentioned above, the National Building Code of Canada requires compliance with CAN4-S115-M, and this requirement is typically found in Canadian project specifications.
However, two other test standards are often referenced as well. The two standards are UL 1479, Fire Tests of Through Penetration Firestops, and UL 2079, Test for Fire Resistance of Building Joint Systems. Both of these standards are referenced in the International Building Code in the U.S. A major d
ifference between UL 1479 and CAN4-S115-M is that the hose stream test is mandatory in UL 1479 in order to obtain a listed system, while it is an optional requirement in CAN4-S115-M.
The hose stream test provides an indication of the integrity of a firestop or assembly during the course of its exposure to fire. It exposes the system or material to impact, erosion and cooling tests in order to determine its overall reliability to perform as intended.
The distinction between test standards and the requirement for hose stream test is important. A specification that referenced UL 1479 would require that listed firestop systems used on that project must pass the hose stream test, which would not be the case if only CAN4-S115-M were referenced.
Given that there exist many, many listed firestop systems in full compliance with CAN4-S115-M that have not passed the hose stream test, the review of submitted firestop systems needs to be conducted thoroughly.
Listing agencies for firestop assemblies are accredited by the Standards Council of Canada under the National Standards System.
Many agencies are qualified to perform the required testing and then to list systems bearing their mark. Agencies such as Underwriters Laboratories, Underwriters Laboratories Canada, Omega Point Laboratories and Intertec are qualified and capable of testing and listing firestop systems in accordance with CAN4-S115-M, UL 1479, UL 2079 and ASTM E2307-04.
Project specifications often make reference to only one specific listing agency which can drastically limit the firestop system solutions and options available on a project. All listings from any of the accredited testing and listing agencies are considered equally acceptable from a code compliance standpoint. Broadening the choice to include them all will help to ensure that the most economical and practical choices of firestop are available.
A designer should never conclude that simply having a firestop product installed in an opening will automatically provide the protection for an assembly that a project specification defines.
Much can be accomplished with a well written project specification. The project team can identify and account for potential shortcomings in interpreting the building code, and they can minimize issues and delays by understanding the limitations and differences between existing test standards.
By selecting the firestop systems early, before building services are installed, the design team can provide direction to the various trades on how to prepare their openings for the services that are to pass through them and ultimately make the firestop installation as economical as possible.
In the end, the timely and correct specification, selection and installation of firestop systems will be in everyone’s best interest.
David J. Volk, P. Eng. wrote this article for Hilti (Canada), in Mississauga, Ontario. Hilti is a member of the International Firestop Council.
1 FSO-10,769, NRC, Institute for Research in Construction, 2005.
2 Recommended IFC Guidelines For Evaluating Firestop Systems Engineering Judgments(EJ’s), International Firestop Council, Terrytown, NY, 2001.