Fire Retardant Treated Wood – Know your stuff!

By November 28, 2018Uncategorized

This post features a few different topics of which cause a variety of head-shaking by me on a regular basis. The goal of this post is to provide insight and clarity into some of the key topics associated with Treated Wood, Fire Retardant Treated Wood, Preservative Treated Wood, and all the other important SEO keywords I could use to appear in your broad search results.

We’ll start simple and increase our level of difficulty as we dive deeper.

So ultimately, what is the purpose of fire retardant treated wood?

FIRE RETARDANT TREATED WOOD (FRTW) is designed to resist to flame spread & smoke development caused by fire and/or fire propagation. That is more or less what the building code calls for, but let’s get real folks, it behooves each and everyone of us to learn how to evaluate products for ourselves. As it pertains to FRTW, you certainly don’t have to be the expert, we can help guide you!

BUYERS/CONSUMERS/SPECIFIERS/ – the next time you evaluate any product for use that claims or references any flame spread or hourly fire resistance ratings, be sure to ask for their test results:

Flame Spread classification: ask to see valid ASTM E84 or UL 723 results.

*the IBC requires 0-25 on flame spread index and 0-450 on smoke development.

**the IBC also requires an extended 20 minutes of testing on top of the initial 20 minute E84 test, so make sure the test results reflect that extended test duration.

Hourly Fire-Resistance rating: ask to see valid ASTM E119 or UL 263 results.

*it is critical that you understand HOW to specify/build a tested & certified rated wall assembly to be compliant by code. If the assembly is not built in accordance with the test documents and assembly design, it’s a building code violation.

**Insulation types (density & thickness) along with drywall (type & thickness) are key ingredients (components) in a fire-rated wall assembly. Use the wrong components, and the assembly won’t work.

Fire treated material are used in critical structural applications, such as fire-rated exterior bearing wall assemblies, to allow sufficient time for occupants to escape and first responders to arrive and begin emergency operations. Therefore, we have “fire-rated wall assemblies” that have been tested for some period of time (1, 2, 3, 4-hours) that were designed to resist fire – versus materials that have a certain flame spread rating (Class-A, B, C).


During fire development in a compartment: a room, wall cavity, attic… surface treatment technology plays an important role in fire development, prior to flashover, which include the components of ignition, flame spread, and the release of heat, smoke and gas. ASTM E84 or UL 723 tests the effectiveness of a treated product during these pre-flashover conditions, or more formally, the test is known as the Standard Test Method for Surface Burning Characteristics of Building Materials.

The fire resistance characteristics of treated materials come into play after flashover has occurred, (above 600C) and the fire has entered the fully developed phase. This is where fire endurance is key, and why products/assemblies are tested for hourly fire resistance in accordance with ASTM E119 or UL 263, which is formally known as the Standard Test Methods for Fire Tests of Building Construction and Materials.’

Also, know this… ALL FRTW is required to be Class-A in accordance with (IAW) section 2303.2 of the IBC, but not ALL FRTW has hourly fire resistance ratings ~ fire-rated assemblies.

If you need an FRTW product with a true 1-hr and 2-hr fire resistance rating, you have slim pickings, unless of course your designer rocks out to REM while working the Component Additive Method (CAM)* for determining fire resistance in an assembly. To quickly determine if an FRTW product has been tested for fire resistance IAW ASTM E119 or UL 263, refer to the product’s third-party evaluation report or the Assembly Design documents. Checkout the FlameTech Fire-Rated Wall Assemblies by clicking HERE.

(*CAM embraces the Ten Rules of Fire Endurance Rating by Tibor Harmathy, and you can learn all about that here if you’d like.)

And speaking of third-party research reports….


“I want a Coke.”

“Kid, do you actually want a coke, or do you want a soda?

Funny way to start this section but you’ll understand why shortly… Often, people ask to see an “ESR” when they want to review a new product, or maybe they say to me, “Well, I went on your site and I couldn’t find your ESR so I stopped there…” To be clear – “ESR” stands for Engineering Services Report. It’s a product name for a specific document, just like FlameTech is my FRTW product’s name. We gave it a name because we want consumers to associate our products with our awesome brand. ICC’s Engineering Services did the exact same thing when they turned an internal process, creating evaluation reports, into a profit center.

If an ESR is not required, can I use another type of third-party research report?

Yes. THE REQUIREMENT, as mandated by the International Code Council, is to have a valid third-party research report and coinciding data from a laboratory or inspection service accredited by the International Accreditation Service (IAS).

Prove it.

To make this easier, the ICC provides a website that allows you to go and check out if some lab or test agency has the proper creds and if they can do the kind of testing and inspections that are required by the code. Click this link RIGHT HERE to check out your product’s credibility.


  1. Visit the website:
  2. Navigate to the third box down from the top “Accreditation #” and enter: “AA-647”
  3. Once the results are returned, select the “View Certificate AA-647” link on the left.
  4. View Intertek Testing Services NA, Inc. Scope of Accreditation which includes wall assemblies and fire retardant treated lumber and plywood.

For what it’s worth, evaluation reports are created based on submittal data captured during product testing to demonstrate compliance with certain aspects of the building code. Regardless of which service created the report, they usually begin with a “SCOPE OF EVALUATION” so that you, the knowledge-seeking reader, can understand what was tested and if/how that pertains to the code. The “common properties” listed below are what SHOULD BE evaluated as it pertains to FRTW products:

  1. Surface burning characteristics
  2. Strength reduction.
  3. Hygroscopicity
  4. Corrosion
  5. Fire Resistance

How does the evaluation report process work? Simple. Submit your product’s testing data to the engineering folks to evaluate your treated product for compliance with the applicable codes and standards, pay some $, and if your ducks are in a row, you’ll get a report.

Here’s a dialed-in Third-Party Evaluation Report

Do we need to continue beating this drum? Just know that there is more than one approved method of getting to a desired end state, you have options… that does seem to be the theme of this post. You deserve better, your business deserves better, and so do your customers.


With the continued increase in seasonal wildfires year after year, the building codes are becoming more stringent thereby requiring increased fire protection. Different cities and jurisdictions have even gone so far as to make their own engineering judgments as to what they deem appropriate levels of fire protection in wood-framed buildings. Furthermore, many jurisdictions are open to the use of alternative materials so this should be music to your ears, it is to ours. Honestly, get used to the idea of fire treatments (yes – that is plural) and get cozy with the building codes so you can best assist your outside-the-box thinking customer while also keeping the conmen at bay. I’m not sure about the rest of the Industry, but we’re busy innovating and have much in store for you! Thanks for reading.