Appeal 18389

OSSC §903.3.1.1, NFPA 13 8.17.1

NFPA 13 as referenced by 2014 OSSC §903.3.1.1., Standard NFPA 13,
NFPA 13, 8.15.7.1
Unless the requirements of 8.15.7.2, 8.15.7.3, or 8.15.7.4 are met, fire sprinklers shall be installed under exterior projections exceeding 4 feet (1.2m) in width.

This project is a 6-story office building with Cross-laminated timber (CLT) panels as the floor framing.

The exterior canopy assembly is located above the main entrance, approximately 11 feet above the sidewalk. The canopy extends for approximately 36’-4” along the east wall (see Figure 1) and 6’-5 5/8” wide. The area underneath the canopy is used exclusively as a sidewalk for pedestrians. No storage of combustibles will be located directly underneath the canopy. The exterior wall of the building is constructed of noncombustible materials in accordance with OSSC §602.3 and combustible exterior projections allowed per OSSC section 705.2.2.

The proposed canopy assembly will be constructed of noncombustible steel frame, as well as a solid Cross Laminated Timber (CLT) underside finish (non-structural). The surface of the wood will be treated with Flamestop II stain (see attached), which is a penetrating wood preservative treatment to reduce flame spread of wood to that of a Class A material as defined in OSSC §803.1.1.

Because the canopy projection exceeds 4 ft in width, the space below the canopy must either by sprinklered or meet the requirements of NFPA 13 §8.15.7.2, §8.15.7.3. These sections permit the omission of sprinklers in exterior canopies where the following exist:
• §8.15.7.2 projections are constructed with materials that are noncombustible, limited-combustible, or fire retardant-treated wood either as defined in NFPA 703, or utilizing a noncombustible frame, limited-combustibles, or fire retardant-treated wood with an inherently flame-resistant fabric overlay per NFPA 701.
• §8.15.7.3 the exposed finish material on the exterior projections are noncombustible, limited-combustible, or fire retardant-treated wood as defined in NFPA 703 and contain only sprinklered concealed spaces.

The CLT panels are too large to be factory fire-retardant treated, and thus an alternate solution is required to protect the canopy CLT panel.

The CLT finish will be protected with a field applied, fire-retardant penetrating treatment. The finishing seal forms a slight intumescent foam layer and carbon char when the treated wood is exposed to fire, minimizing the potential for flame propagation or smoke evolution. (See Intertek E84 Test-Attached) Fire Coating Flame Stop II will not require reapplication if not exposed directly to weather. (Recommended inspection at 5-year intervals)
The coating of the surface will reduce the flame spread, meeting the intent of NFPA 13,8.15.7.3. In addition to reducing the flame spread to less than 25 (Class A), the stain will provide a layer of intumescent char under heat, thereby creating a barrier to ignition and thus fire proofing.

It is not anticipated that a credible fire scenario will occur inside the canopy assembly as the only source of ignition are UL listed recessed lights. The canopy structure is limited to non-combustible materials and an air gap is provided to ensure heat cannot build up during an event.

We examined credible fire scenarios below the canopy, and the effect they will have upon CLT surfacing. The canopy bottom is to be installed a minimum height of 11 ft. above the exterior grade/finished sidewalk elevation. Potential fire scenarios include; a fire that may occur within an exterior trash can left underneath the canopy, or packages on the sidewalk. The canopy is open to the exterior on three sides. Since the flames would not be able to directly impinge upon the assembly and the canopies are open on three sides, heat will not be able to collect underneath the canopy at a rate similar to those experienced within the ASTM E 119 test furnace. It is anticipated that the CLT ignition point (550 degrees) from a credible fire scenario underneath the canopies would be nearly impossible.

With surface treatment penetrating into the wood surface on all exposed sides, the material would match the surface burning characteristics of generally accepted (non-combustible) tropical hardwoods.

This Appeal is similar in intent as to past granted appeals in canopy/overhangs with wood.

13089, 6 ft overhang using surface treatments
15698 IPE tropical wood Class A decking
18194 Cumaru tropical wood Class A Cladding on deck

In the attached EJ, prepared by an Oregon Registered Fire Protection Engineer, we have reviewed the proposed canopy assembly to NFPA 13 requirements for sprinkler protection. Appeals in the past have successfully been granted with the use of tropical hardwood materials which have a low potential surface flame spread. The CLT panel proposed with the penetrating surface treatment, will meet the surface fire resistance of those wood materials with a Class A fire rating.
Therefore, it is my opinion that proposed design for the canopy assembly, including a CLT underside finish meets the intent of NFPA 13 §8.15.7.3 for elimination of fire sprinklers.