Question #118889. Asked by star_gazer.
Last updated May 16 2021.
The introduction of holes reduces the needed volume of clay through the whole process, with the consequent reduction in cost. The bricks are lighter and easier to handle, and have thermal properties different from solid bricks. The cut bricks are hardened by drying for between 20 and 40 hours at 50-150 °C before being fired. The heat for drying is often waste heat from the kiln. European style extruded bricks / blocks are use in single wall construction with an applied finish inside and outside. They have many voids, the voids being a greater fraction than the solid, with thin walls of fired clay and come in 15-25-30-42-50 cm widths. Some models have very high thermal performance suitable for Passivhaus type buildings.
1. Holes save raw materials for the manufacturer.
2. The holes make the bricks weigh less.
3. Holes allow a consistent heat distribution throughout the brick when it is cooking in the kiln, resulting in a thorough and even cure.
4. Most important, the holes allow the masonry structure to be built more securely. The brick is turned during construction (you won't see the holes on the finished product) allowing mortar to fall inside. These holes, filled with mortar provide a "keyway," locking one brick to the next. The holes can also accommodate rebar if needed.