Standard clay and shale bricks are ceramic building units used in construction. The definitive answer to whether these common building blocks can catch fire is no. Standard bricks are classified as non-combustible, meaning they do not ignite or sustain a flame. This article explains the material science behind this fire resistance and details what happens to bricks when exposed to the extreme temperatures of a structure fire.
The Non-Combustible Nature of Bricks
Bricks are primarily composed of inorganic mineral compounds, lacking the carbon-based organic material necessary for combustion. Fire requires heat, an oxidizer, and fuel; bricks do not supply the fuel element. Unlike wood or synthetic siding, bricks are chemically inert when exposed to flame temperatures.
This inability to burn means a brick wall will not contribute to a building’s fire load. When flames touch the surface, the material does not decompose into flammable gases or melt away. The non-combustible classification allows bricks to act as a passive barrier against fire spread.
How Brick Manufacturing Creates Fire Resistance
The process of making a brick is essentially a test by fire, which permanently establishes its resistance to future heat. Standard bricks are formed from a mix of clay and shale, which are then dried and fired in large industrial kilns. The temperatures inside these kilns typically range between 1,000°C and 1,100°C (1,832°F to 2,012°F).
This high-temperature firing chemically alters the raw materials, fusing the mineral components together into a hard, dense ceramic structure. Any trace organic matter or moisture within the clay is burned off during this intense thermal process. Since the brick has already survived temperatures far hotter than a typical house fire (which generally peaks around 650°C), it is rendered incapable of further combustion.
Structural Damage from Intense Heat Exposure
While bricks do not burn, they are not immune to the destructive effects of prolonged, intense heat. A common type of damage is called spalling, where the face of the brick cracks, peels, or pops off. This damage is primarily caused by thermal shock, which occurs when there is a rapid temperature difference between the surface of the brick and its cooler interior.
The high heat causes the brick face to expand quickly, while the core remains relatively cool, leading to internal stress. If the brick has absorbed moisture, the water near the surface can turn to steam and expand rapidly, creating internal pressure that forces the outer layer to break away. Sustained exposure to fire temperatures, especially above 600°C, can also weaken the brick’s overall compressive strength, compromising the structural integrity of the wall itself over time.
Practical Fire Safety Applications
The non-combustible properties of brick make it an effective material for fire safety in construction. Brick walls serve as dependable fire barriers because they do not fuel a fire and significantly slow the transfer of heat. This delay provides occupants a longer window for safe evacuation and gives emergency services more time to control the blaze.
Due to their low thermal conductivity, thick masonry walls can achieve fire resistance ratings of up to four hours, depending on the wall assembly. This performance is recognized by building codes and insurance companies, often resulting in lower premiums for structures built with brick. Building with brick incorporates a high degree of passive fire protection.