Caulking of Concealed Connections at Glulams

Conor Lenon — Fri, 02 May 2025 15:45:51 +0000

Simpson and other manufacturers make connections create concealed beam hangers for Glulams that are fire-rated. https://www.strongtie.com/miscconnectorsforengineeredwood_engineeredwood/cbh_hanger/p/cbh

However, it is unclear if it is necessary to caulk the joint between the beam/column or beam/beam. It seems to be based on jurisdiction / engineering judgement (and theoretically, would be in scope of the architect to determine - but in mass timber fire has a more direct structural impact thus it's becoming more important for engineers to be involved in rating discussions).

I'm curious what resources anyone here points to to justify the need or lackthereof of caulking at these connections?

Fire Retardant Coatings, vs. Fire Retardant Treated.

HEBlomgren — Thu, 12 Dec 2024 23:35:28 +0000

Fire retardant coatings, vs. Fire retardant Treated wood. There is a difference and I see a lot of confusion in specifications. APA and FPL did this study on applying FRT to glulam for example. It would be good to discuss this topic to make sure specifiers and suppliers are coordinated. Please share your experiences!

https://www.apawood.org/Data/Sites/1/documents/technicalresearch/final-report-frt-glulam-r1.pdf

**************More Detail below added at Ling's suggestion - Dec 13 2024**************

My question starts with the design team and what a code compliant specification is. This is a question specific to design under the International Building Code. The Code is complicated and can make for confusion. The backbone of the Code of course is based on Performance Testing to assure life safety. That is where we can have a good time with this Forum if we get the dialogue going between designers, Code writers, builders, and scientists!

So - Here is the case that came up most recently for myself. I work at a construction company that bids, procures, and installs mass timber buildings. The projects is a 1 story Type IV building. Some parts of the primary structure extend outside the building envelope, including columns and beams and roof soffits. There is also a prominent wood canopy that extends over a drive-up to the building.

The architect has specified the use of an exterior fire retardant coating on the exterior wood members. I have been able to deduce they are doing this to preclude the use of sprinklers on the exterior of the building. Per NFPA 13, there is an allowance to not have sprinklers in these locations if the wood is "Fire retardant treated in accordance with the NFPA 703.

This is an example of the flame retardant coating product you can find. https://flamecheck.com/product/fif-clear-coat-x/?srsltid=AfmBOoo1h19eeY-KaWyq2I-QFOdJ-EVxqQq7Q6rSr7oCtBBZ_Ix9Ci3w

The confusion here then is that specifiers are specifying this coating system that is not a fire retardant treatment per NFPA. So the confusion is over the single word of coating vs. treatment.

This is an issue that raises and RFI on projects and can take weeks to resolve.

The APA/FPL document I've referenced is clearly is using FRT treatment (i.e. chemicals applied by a pressure process) and not a coating. There are no commercially available FRT glulam products that I'm aware of (there is an glulam FRT rim board product with UL report that I've found, but that is not a glulam member per ANSI A190.1).

Thanks!

Fire - Timber Engineering Forum

Caulking of Concealed Connections at Glulams

Fire Retardant Coatings, vs. Fire Retardant Treated.