thanks

So it looks like there are pathways to follow for fire-coating for indoor use. I guess by the end of the day, it is a matter of what is allowed by JHA. But it would be nice to have an up-to-date flowchart for this @sebrenemanse

WoodWokrs: please make one of these 🤣 

ICC-ES has developed several Acceptance Criteria (AC) documents (AC 47, AC124, AC479, and AC516) to evaluate fire-retardant-coated wood products, so there is a pathway for evaluation of these products for use with wood as an alternative to FRTW. These AC typically include evaluation of the flame spread performance, effects on mechanical properties of the wood, corrosivity, and durability of the coating when exposed to weather during construction and storage. To my knowledge, none of these have criteria for exterior use. 

Another issue to watch out for is that coatings can be used to meet the interior finish requirements of the code (i.e., Class A, Class B, Class C ratings).  These applications typically do not require as extensive of evaluation and a coating manufacturer may have an evaluation report that is limited to that application.    

It is critical to note that "Class A" fire performance is not equivalent to the flame spread performance required for FRTW.  The FRTW test is much more severe.  Many coating manufacturers have listings demonstrating "Class A" performance but few meet the more difficult requirements for FRTW.  Fewer yet will meet the construction/storage durability requirements in the various Acceptance Criteria.

the real question is: are we there yet? (does the market have enough cases of this application to warrant some efforts to develop such a guide yet?) @heblomgren

One thing that wasn’t mentioned, and why I'm adding my woefully late response, is the potential need for preservative treatment of the glulam since the project included exterior applications. From AWPA: “Some preservatives do impart a degree of fire retardancy, and some fire retardants can act as preservatives to some extent.  In general, fire retardant treated wood should not be used where preservative treatment is required, nor should preservative treated wood be used when fire retardant treated wood is required.” I am unaware of any dual (fire and preservative) treatments on the market.

If there is enough market for fire treatment for larger members, there might be someone who will find a way to get it done... 

Or if we just test the coated option on large members and prove they are equivalent?

Hi @Ling -- testing has shown that coatings aren't equivalent and that performance of FR coatings decreases rapidly after they've been exposed to weather. See for example: https://onlinelibrary.wiley.com/doi/full/10.1002/fam.2506

@heblomgren - thanks for sharing. Yes- rim board was one of the applications we were looking at FRT treated mass timber for Type III construction-- you need FRT when it is incorporated in the exterior wall, so that was the main drive for the research we had done previously. However, if that company is able to produce FRT rim board glulam, their treater might be able to treat other glulam as well.