Structures built from concrete masonry units (CMUs) not only help prevent fires because of their noncombustible nature, they are extremely effective in slowing or blocking the spread of flames in the unlikely case of fire. This extra time is critical in saving lives and mitigating property damage.  

video produced by the National Concrete Masonry Association demonstrates how CMU compares against walls made of drywall and fiber-reinforced gypsum panels under fire conditions in the ASTM E119 laboratory test. 

After the CMU wall was exposed to fire for two hours, water from a fire hose bounced right off it. The drywall wall failed completely after 37 seconds, while the gypsum panels crumbled after just 10 seconds. 

MaterialTime to FailureWall Damage/Repair
Concrete Masonry WallNo DamageNone/Clean
Dry Wall37 secondsDisintegrated/Rebuild
Fiber-Reinforced Gypsum Panels10 secondsCrumbled/Rebuild

What This Test Means To You

Regardless of the structure type, building materials play a significant role in safety. Walls made from CMU do not burn and are proven much more effective at containing a fire. This is of particular importance in multi-family residential units such as dormitories and apartment buildings. These buildings are more at risk of fire hazards due to multiple kitchens, furnaces, space heaters and other potential fire sources.

Fire containment is another key benefit. Sleeping occupants have less time to escape, making the containment of the fire to its room of origin all the more important. CMU passes the test, keeping blazes to the room of origin 93% of the time. This compartmentalization allows firefighters more time to extinguish the blaze before it spreads.

Another benefit is that noncombustible block structures and walls do not add to the buildup of toxic gases and smoke in a fire. Smoke inhalation is a primary cause of death in structure fires. 

CMU is also an economical way to protect your property investment, as block exposed to fire requires only cleaning and some repair. Just 1% of block buildings exposed to fire are demolished. 

Interested in using CMU in your next project?
Use the NCMA CMU fire resistance calculator

For these reasons and more, building with concrete masonry simply makes sense. To learn more about the benefits of block, call the Southeast Concrete Masonry Association at 704-228-0474 or email

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