Fire Retardant Coatings, vs. Fire Retardant Treated.

Well, I am no expert in Fire... but

@heblomgren Could you be a bit more specific on the confusions you saw?

maybe @samzelinka can also share his experience and if anyone reached out to him for these results. As one point we can pull APA in:)

@ling I've added an update to my post from yesterday -- see above.

Hi Hans-Erik and Ling

The project we did with APA on FRT treated glulam & LVL was also related to the codes. However, the specific use case we were looking at was for Type III construction, where exterior walls are required to be framed with fire retardant-treated wood (FRTW) or non-combustible materials.

As you are probably aware, FRT treatments can negatively affect the strength of wood and there are methods within ASTM to calculate the strength reduction factors for FRT treatment. The study we did went through these standard tests to calculate the strength reduction factors for glulam and LVL.

Even for that study, where we weren't looking at what I would consider large mass timber elements, we had problems finding treaters who were able to treat with FRTs to treat "large" glulam and LVL.

After we wrote the report I stopped following APA's code efforts as it related to FRT mass timber. However, as far as I know, no one ever moved forward with commercializing an FRT treated mass timber product.

Which then brings it to the heart of Hans-Erik's question-- whether FRT coatings count as FRT treatment for code purposes. As I read Hans-Erik's case study, he answers it himself. However, I've forwarded this to my colleague Laura Hasburgh and hope that she will chime in as I know that she has a lot of great knowledge about both the code and the performance of fire retardant coatings.

@samzelinka Thanks for the response.  Here is one commercial use where FRT GLT is classified for a limited end use of rim-board.  UL classified as shown.  https://rosboro.com/product/x-rim-frt/

@samzelinka good point... those large size members are hard to treat as smaller ones...

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?

Posted by: @ling

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@samzelinka good point... those large size members are hard to treat as smaller ones...

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.

@heblomgren and @samzelinka, you are correct that the code (IBC Section 2303) defines FRT as wood impregnated with chemicals by a pressure process or other means during manufacture and that coatings are not recognized as equivalent. It is my understanding that FRTs are generally not recommended for large timber or glulam since the chemicals reduce the design properties of the wood and may not be compatible with the adhesives used. However, if you do find an option, you will want to confirm it is an exterior FRT that underwent the additional required accelerated weathering tests to ensure the chemicals do not leach.

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.

@lhasburgh great point about the AWPA language that "fire retardant treated wood should not be used where preservative treatment is required"! Thanks for adding that to the discussion!

@lhasburgh thanks for the insight. It looks this is still kind of a "wild west" type of situation (people just doing what they feel they can justify and get through the permitting process). The market have needs but the regulation and products have not catch up yet. There is nothing wrong with that, as no new things will be built if everyone just wait until the rules are out. But as the market and application grows in these exposed and outdoor usage cases, it would be nice to have a guideline or recommended practices... either by FPL or AWPA or AWC.

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

Ah, this is a Wild West subject.  It doesn't help that the "fire retardant" phrase is applied to impregnated treatments meeting the IBC Fire Retardant Treated Wood definition in IBC 2303.2 and for coatings that are used to meet the flame spread index for certain finish requirements.

Hoover Treated Wood Products does have an FRTW treatment, ExteriorFireX, which meets some preservative treatment requirements.  Now, I think the application of this product is more for sole plates in contact with foundation concrete in Type III construction or exterior wood siding in WUI applications and similar, not large exposed structural components.

The building code (IBC) has a definition, provisions, and performance requirements for fire-retardant-treated wood (FRTW) but does not have provisions for fire-retardant coatings, which have to be approved through the alternative materials clause (e.g., 2021 IBC 104.11).  

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.

Thanks for the background @linville

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 🤣 

@sebrenemanse Thanks.  In December I had a project where I had to dig into this topic.  I found the Technical Director at AWPA who has further helped put a tighter circle around this Code Acceptance topic...   He has been super-helpful.  But upon reflection, I must say that sorting out fact from fiction on this particular topic is very hard to access.

@heblomgren could you help send the link of this discussion to the AWPA director? He does not have to comment, but it would be nice so he knows the discussion.

thanks