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Where unconcealed connections are desired,justification Interior Finish Requirements of the fire-resistance rating through other means acceptable When using exposed mass timber framing, structure also be jurisdiction shall be provided.Some projects havetied functions as finish making it necessary to consider interior intumescent paints to provide protection for exposed finish provisions of the code. IBC Chapter 8 provides connections. requirements and limitations for items such as flame spread In 2017,three different configurations of glulam beam-to- index, heat release and flashover,and flame propagation column connection fire tests were conducted using the limitations for interior finishes. Section 803 covers wall and ASTM E 119 time-temperature curve.The completed fire ceiling finishes which are the most common applications tests and supporting reports allow engineers and architects of exposed mass timber. Exposed heavy timber elements to specify these tested connection assemblies and satisfy complying with the requirements of Type IV construction the requirements noted above.All three tests consisted are not subject to interior finish requirements, except in of a glulam beam and column connected with one or two specific egress passages, per IBC Section 803.3. Due to prefabricated hangers. Each connection was also structurally this,an argument could be made that any exposed mass loaded. Ratings of 1 hour and 1.5 hours were achieved. timber elements,even those in construction types other The full report and fire test documents are available in the than IV,would not be subject to interior finish requirements. Think Wood Research Library which includes mass timber However, if a jurisdiction is applying these requirements to research from around the world exposed mass timber elements used in Types I, II, III or V, the following provisions exist. A qualified professional can also be retained to perform an engineering analysis on a proposed connection detail in order IBC Section 8031.1 defines how materials are classified for to evaluate its performance under fire conditions flame spread smoke-developed index performance. It states: Interior wall and ceiling finish materials shall be classified in accordance with ASTM E84 or UL 723. Such interior finish materials shall be grouped in the following classes in accordance with their flame spread and smoke-developed indexes. 41 Class A. Flame spread index 0-25;smoke-developed index 0-450 Class B:Flame spread index 26-75;smoke-developed index 0-450 Class C:Flame spread index 76-200;smoke-developed index 0-450 IBC Table 80311 provides the requirements for interior finish class(A, B or C),which is a function of the building's \ occupancy, whether or not it is sprinklered,and where in the building the finish is located. For sprinklered buildings,most occupancies and building areas require a class B or class C finish per Table 9. AWC's Design for Code Acceptance I -Flame Spread ..' Performance of Wood Products Used for Interior Finish (DCA 1) lists flame spread values for a number of wood i r species and wood panel products.Table 10 shows values for common species used in softwood mass timber framing members. Mass timber product manufacturers have 471- conducted ASTM E 84 tests on their products and have found 4 results matching or exceeding those presented in DCA 1 ;n S rf I 14