Timber’s Fire Testing Farce

Aaron Fisher | January 7, 2026

There is an air gap between material fire standards and building codes being exploited by the lumber industry, which is endangering people and first responders.

Between Material Standards and Building Codes

Material standards define the minimum performance of a construction material. Codes are carefully crafted using these performance values to give engineers and other stakeholders confidence that buildings designed using this guidance will function as expected. Codes reference these standards, and their respective committees often collaborate, sharing personnel and information so that our structures work as expected.

However, this set-up isn’t prepared for a group interested in subverting the rules.

Lumber codes were largely developed from practical experience around residential construction. Historically there was a large degree of redundancy and overdesign in these structures. As an example, most 2-story houses could have an additional story added should they need to be expanded. With this origin in mind, wood stud construction has been historically limited to 4 stories.

Financial incentives in cities leads to the densification of buildings– that is we add square footage to our properties by building vertically (more floors). Where land is expensive this means that that we tend to built up instead of out. While, they have found a nice niche in 4-story multifamily structures, code has effectively prohibited the use of wood in taller buildings, to the frustration of the lumber industry. Above that, lumber buildings have trouble with the fire codes, which only gets more challenging the higher you go.

Skipping the Hose Test

Seeing as they were missing out on these opportunities the lumber industry has exploited an air gap between fire codes and the building code. ASTM E119 is the critical test and determines how long a material remains structurally functional in a building during a fire. It’s what allows someone to say an assembly is 2-hour fire rated. And while it requires testing for exposure to fire it does not mirror real-world application; specifically hose testing is optional. The building codes often mandates the hose test rendering skipping this part of the test moot in practice.

Furthermore jurisdictional codes mandate fire department response times that lead to a fire department being on-site protecting the building occupants well before the structural time limit is breached. Firefighters when they arrive on scene are taught to 1) save lives and 2) extinguish the fire. That 2nd item means turning on the hoses and getting at the flames ASAP.

This is the crux of the issue. Many structural materials (concrete, glass, steel) get hot but don’t fundamentally change in a fire—wood does. In a fire wood either burns or chars. Burning wood turns it into a gas diminishing the material in the structural element. Charred wood becomes brittle but retains most of its structural strength (ever picked up a campfire log the next morning?). This difference has allowed wood to show that in the absence of a fire department or sprinklers the structure is still standing at the noted time.

Endangering Lives and First Responders

In their words: “The 2017 tests at the ATF facility and 2020 testing in Sweden with the RISE Institute included sustained four-hour fires without sprinkler or fire department intervention.”

This caveat is the game. When water from either a sprinkler or a fire hose hits this brittle material it knocks off the char 1) diminishing the size of the structural element and 2) re-exposes wood which is fuel for a fire. This argument is disingenuous at best, and more likely malicious. It puts the entire fire fighting profession in real danger. A hose is thought of as a tool to fight a fire, but it might as well be dynamite for the structural wood elements engulfed in flames. Simply put it does NOT meet the building code as currently constructed.

They are exploiting this loophole though to assuage politicians that their product is fire-safe, when it really isn’t. In the pursuit of profits the lumber industry is endangering our first responders and the folks living in these buildings.

Sustainability Epilogue

Oh yeah by the way their arguments on “sustainability” are disingenuous which is why we were even considering this material in the first place.

The Receipts

The Lumber Industry in their own words:

Fire Tests for Code Changes in the ICC Pioneering fire testing initiatives led by the International Code Council, American Wood Council, and the USDA Forest Service, with support from Susan Jones of atelierjones, provided the scientific foundation for code changes enabling mass timber buildings up to 18 stories. The 2017 tests at the ATF facility and 2020 testing in Sweden with the RISE Institute included sustained four-hour fires without sprinkler or fire department intervention. The 2020 results led to further code updates in 2022, including changes to the Type IV-B provisions that increased the allowable percentage of exposed wood ceilings and beams from 20% to 100%. Source.

Fire Performance: When exposed to fire, mass timber chars at a consistent rate (approximately 0.65 mm/min), creating an insulating layer that protects the structural core. Tests have demonstrated that unprotected mass timber assemblies can achieve 2-hour fire ratings under standard testing conditions. Source

The Code Loophole:

From ASTM E119 §7.6.1 Hose Stream: Where required by the conditions of acceptance, a test shall be conducted to subject the test specimen described in 7.6.2 or 7.6.3 to the impact, erosion, and cooling effects of a hose stream. The hose stream shall be applied in accordance with Practice E2226. The water pressure and duration of application shall be as prescribed in Table 1 of Practice E2226