Refractory Bricks: Sizes and Shapes

Refractory bricks, also known as firebricks, are essential materials used to line furnaces, kilns, fireplaces, and other high-temperature equipment. But not all refractory bricks are created equal. They come in a variety of sizes and shapes to suit different applications.

Standard Sizes

The most common size for a typical refractory brick is 9 inches long by 4.5 inches wide by 2.5 inches thick. This is considered a “standard brick” size. However, there are many variations on this standard size. Some common sizes include:

  • 9″ x 4.5″ x 3″
  • 9″ x 4.5″ x 2.25″
  • 8″ x 4″ x 2.5″
  • 7″ x 3.5″ x 2.5″

Larger sizes are also produced such as 9″ x 4.5″ x 4.5″ bricks. These jumbo bricks have higher weight and lower porosity. Smaller brick sizes are available too for specialized uses.


In addition to different sizes, refractory bricks also come in various shapes. Some common shapes include:

  • Rectangular – The basic straight brick shape.
  • Wedge – A wedge-shaped brick used for lining curved furnace walls.
  • Bullhead – A brick shaped like a bull’s head with one end larger than the other. Useful where the wall thickness increases.
  • Arch – A brick shaped like an arch or voussoir for constructing arched furnace doors or entrances.
  • Cupola Block – A curved, elongated brick for lining cupola furnaces.


Most refractory bricks range from 2 inches to 3 inches thick. Thinner bricks around 1.5 inches are made as well. The thickness affects the insulating properties. Thicker bricks generally provide better insulation. But thinner bricks are useful where space is limited.

For most furnaces and boilers, a 2.5 inch thick standard firebrick is sufficient. But insulation bricks used on the exterior can be 3 inches or more thick for added insulation. The temperature, application, and desired efficiency determines the ideal thickness.


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