How Fire Retardant Chemicals Work in Treated Lumber
When a project calls for fire treated wood, most builders and contractors know it’s about safety and code compliance — but how does it actually work? What’s happening inside the wood that makes it more fire resistant?
The Science Behind Fire Retardant Chemicals
Fire needs three things to burn: heat, fuel, and oxygen. Fire retardant chemicals change the way wood reacts when exposed to flames by interfering with that process.
What Happens Inside Fire Treated Wood
- Heat Exposure – When fire treated wood is exposed to flames or high heat, the chemicals inside begin to activate.
- Chemical Reaction – The fire retardant chemicals promote char formation rather than open flame. This char layer acts as a barrier, slowing how fast heat and fire can travel through the wood.
- Reduced Combustion – By limiting flame spread and reducing smoke generation, the treated wood helps meet critical fire safety standards and gives people more time to react in a fire situation.
This process is what allows Biewer FRTW to achieve a Class A flame spread rating (ASTM E84) — the highest rating possible — meaning it slows the spread of flames significantly compared to untreated wood.
Benefits of Fire Treated Wood
- Code Compliance Made Simple – Meets IBC and IRC requirements for fire resistance.
- Peace of Mind – Extra protection for multifamily, commercial, and municipal buildings.
- Better Performance – Biewer FRTW is kiln-dried after treatment (KDAT), making it dimensionally stable and easier to work with on site.
Why Choose Biewer FRTW
Not all fire treated wood is created equal. At Biewer FRTW, we use proven fire retardant formulations that are safe to handle, non-corrosive to metal fasteners, and backed by third-party testing. Plus, our technical support team is available to answer questions and provide documentation to keep your project moving smoothly.
The Bottom Line
When you understand how fire treated wood works, you can appreciate why it’s a critical part of safer construction. The fire retardant chemicals inside don’t just check a box — they help protect buildings, reduce risk, and keep people safe.
Looking for the best solution for your next project? Choose Biewer FRTW for quality you can trust, performance you can rely on, and expert support every step of the way.