What is Fire Retardant Lumber?

Fire retardant lumber is lumber that has been chemically treated to resist ignition and flame-spread with the primary goals of giving people more time to react to the fire and to minimize damage to the structure.

How Does Fire Retardant Lumber Work?

When it comes to fire, there are three things that are needed for it to thrive.  Those three things are: oxygen, heat, and fire.  In this case, wood is the fuel for fire.  The cellulose and lignins that make up wood produce flammable gases when exposed to heat.  Once exposed, those gases in combination with oxygen fuel the fire and continue to expand it.  It should also be noted that fire retardant does not make wood non-combustible.  Fire retardant wood exposed to fire over an extended period of time will eventually burn.

The fire retardant treatment causes wood to burn differently than regular wood. When introduced to flame, the chemicals produce a non-combustible gas that resists ignition by producing carbon dioxide and water vapor to dilute the combustible gases.  As a result, a layer of char that slows the spread of fire.

What’s in Fire Retardant Lumber?

Depending on the expected exposure, there are two types of fire retardants; interior and exterior.  Fire retardants utilized for interior applications are water soluble and must be protected from exposure to water.  For this reason, interior applications of fire retardant lumber must be kept dry.  For exterior applications, fire retardants must be able to withstand extended and prolonged exposure to water and other weather conditions.

How Retardant is Applied

Fire retardant lumber is pressure treated through a process similar to that for normal pressure-treated wood. The wood is first kiln dried to remove moisture from its cells and then placed into a pressurized vessel in which the fire retardant chemicals are forced deep into the wood’s cell structure. The final step is to put the wood back into the kiln and dry it after treatment.

Discover More

American Pole & Timber offers fire retardant lumber for both exterior and interior applications.  Our treatments will ensure your structure is code compliant.  So, when fire retardant wood has been specified for your project, call us or contact us online for quotes and availability.