The air leakage rating adds smoke-resistant properties to assemblies that need them. The requirement that a fire separation resist the passage of smoke for a set period invokes the need for an L-rated firestop system.
The position of the Firestop Contractors International Association (FCIA) is that even when fire separations do not have a fire-resistance rating, a tested and listed firestop system should be used to get the air leakage rating for smoke-resistant properties. Why? Most commercial, industrial, and institutional occupancies use wall and floor assemblies approximating a fire-resistance-rated assembly, even when not rated. If the assembly approximates a tested assembly, then the L-ratings provide the closest thing to a complete tested and listed assembly offering quantified protection. The L-ratings are the ‘suitability for use’ statement of a firestop product in a specific application (i.e. for smoke). Since smoke travel is a crucial item to protect against, it makes little sense to specify anything less than an L-rated firestop system in assemblies that are considered non-fire-resistance-rated.
For firestopping, NBC states the abutment, gap, void, breach, opening, annular space size, penetrating item, covering, or similar is to be sealed based on CAN/ULC-S115.
NBC Article 3.1.9.1 (Firestopping of Service Penetrations) states:
Except as required by Sentences (2) and (3), and permitted in Sentences (4) and (5), penetrations of a fire separation or a membrane forming part of an assembly required to have a fire-resistance rating shall be:
a) sealed by a firestop system that, when subjected to the fire test method in CAN/ULC-S115, “Fire Tests of Firestop Systems,” has an F rating not less than the fire-protection rating required for closures in the fire separation in conformance with Table 3.1.8.4., or (50pa, plastics)
In NBC, there is one exception to the requirement for firestop systems tested to CAN/ULC-115. It is a very minor exception and requires ‘casting in place’ the service penetrating items when concrete is poured. It is:
b) cast in place (see Appendix A).
This exception allows concrete, equal thickness to the wall or floor, for a limited number of penetrating items and opening size. However, some penetrating items may not be compatible with cement-based products, so one must verify compatibility with cement-based products used where firestopping contacts other parts of the assembly, such as copper piping.
In short, any service penetrating items and abutments, continuous breaches, gaps, voids, or openings made for independent movement or compatibility through one or both sides of fire-resistance-rated construction should be treated with firestopping tested and listed to CAN/ULC-S115, unless they fall under the exception (b).
Without firestop system listings from a laboratory directory such as ULC’s and manufacturers’ installation instructions, it is difficult to know the fire resistance rating’s duration and whether there is protection. Some manufacturers provide engineering judgments (sometimes in conjunction with the testing laboratory or fire protection engineer) when no tested and listed system from any firestop manufacturer exists to address a field condition.
| RESISTING EXTERNAL FIRE WITH ROOFS |
| Roofs and the type of fire resistance they require have been questions in people’s minds for years. The meaning is all in the definitions. Underwriters Laboratories of Canada’s (ULC’s) test method, CAN/ULC-S101, Standard Methods of Fire Endurance Tests of Building Construction and Materials, reports results of tests of the time in minutes or hours an assembly of materials resists flame passage, supports a load, and limits temperature rise on the non-fire side of the assembly. The assembly includes the roof deck and any sprayed or intumescent fire-resistive materials (SFRM or IFRM) applied, any firestopping of service penetrating items through holes in the roof (if required), and the roofcovering (including air barrier, insulation, and roofing membrane material).CAN/ULC-S107, Methods of Fire Tests of Roofcoverings, measures the ability of a roofcovering to resist fire from a source outside the building. This test assesses the material based on four criteria. First, intermittent flames might occur as they travel across a roofcovering. Second, spreading flames occur when flaming or combustible material is on fire (evaluating the ease at which flames travel). Burning brands occur on roofs when burning debris falls on it from other structures, trees, or similar. Flying brands occur when a flaming roofcovering breaks into pieces and is carried to another part of the roof while on fire.
After completion of the fire test, a rating such as Class A, B, or C is assigned. Class A roofcoverings:
Class B is the same as Class A, except it offers moderate fire exposure and protection to the roof deck from above. Class C covers light fire exposures and provides a measurable degree of protection to the roof deck. Burning brand sizes vary based on rating class. All classes are conditioned in an oven at 41 to 49 C (106 to 120 F) for at least 24 hours. Class A uses a grid of 305-mm (12-in.) square and 57-mm (2-in.) thick Douglas fir lumber free of knots and pitch pockets, with nominal 25x25x305-mm (1x1x12-in.) strips of wood dressed on all four sides to 19×19 mm (3/4x3/4 in.), placed in three layers of twelve strips each. These strips are spaced 6.35 mm (¼ in.) apart, and placed at right angles to those in adjoining layers on one face in a diagonal pattern. The Class B burning brand is smaller at 152 mm (6 in.) square, while the Class C is a piece of dry, nonresinous white pine lumber free of knots and pine lumber, 38x38x20 mm (1 ½x1 ½x8/10 in.) thick with saw kerfs applied as specified. To get the Class A rating, a large burning brand is used in the fire test. Class B and C are subjected to smaller burning brands. Slope limitations are stated in the listing, along with deck construction supporting the roofing system and any required or optional barrier boards, ply sheets, and surfacing. This ‘topside’ roof test is not a fire resistance rating test and does not establish an hourly rating. Another test standard provides fire-classified assemblies evaluated by either large-scale fire testing or using procedures described in CAN/ULC-S126, Standard Method of Test for Fire Spread Under Roof Deck Assemblies. This test covers flame spread under the roof deck. To illustrate, let it be assumed a roof assembly is one- or two-hour fire-resistance-rated. It has a listing from the UL/ULC Online Certifications Directory, fire resistance section, or other accredited testing laboratory acceptable to the authority having jurisdiction (AHJ). Can a roof system with only a CAN/ULC-S107 rating be used when the roof assembly is to be fire-resistance-rated to CAN/ULC-S101? The answer depends on the hourly fire-resistance-rated assembly listing. Some fire-resistance-rated assemblies are proprietary and require certain roof assembly materials specified by the manufacturer that paid for the testing. The manufacturer of each material in the assembly can certainly be specified in the tested and listed system. It may also be stated as a generic product category, such as polyisocyanurate (polyiso) or mineral fibre. The maximum or minimum thicknesses of insulation is sometimes specified, and the decking gauge and thickness may be as well. Where the listing is manufacturer-specific, each material would be listed, from the SFRM or IFRM to the roof deck, air barrier, roof insulation, and roofcovering material (including surfacing). This testing should include any vegetated roof overburdens, as well as new photovoltaic (PV) panels used on the roof. If they are used on the rooftop, they should be tested and listed to the same requirements as the roofcovering membrane. As mentioned, other fire-resistance-rated systems require the fire resistance from the underside to be tested and listed and instead allow a generic roofcovering or insulation. The listing might state single-ply, built-up (BUR), or modified bitumen (mod-bit) roofing, polyiso insulation, or ballasted or smooth roof surfacing. Any Class A, B, or C system selection should meet ULC test standard requirements referring to the topside fire exposure. It may also require flame spread and smoke development ratings. It is possible to spend much more time discussing test standards for fire resistance for many building elements, from walls and wallpaper to equipment used in and on buildings. Learning the difference between hourly fire-resistance-rated and topside fire spread protection for buildings is an important first step. |
