Breeze blocks, also known as concrete blocks or concrete masonry units, are a moulded concrete and aggregate product used for building structural walls. Breeze blocks feature an open-core design, typically two cores per block, that allows for adding both reinforcement and insulation to structures. Breeze blocks were mass-produced as early as 1904 and are available for both large-scale construction projects as well as small home improvement projects.
According to the Masonry Institute of Washington, the first concrete masonry unit was manufactured in 1882. Early masonry blocks were much larger in scale than modern breeze blocks, measuring 30 feet long by 8 inches wide by 10 inches high. The size of these early blocks demanded an on-site manufacturing process. By 1904, concrete blocks had shrunk in size to 24 inches long by 12 inches wide by 8 inches high. These smaller-scale blocks could be produced at a manufacturing facility and transported to the job site.
Modern breeze blocks are constructed using a mixture of water, Portland cement and aggregate. Breeze blocks for special applications may also include additives such as colourants. The production of breeze blocks begins with moulding the wet mixture into shape and allowing a short hardening time prior to removal from moulds. Breeze blocks are typically steam-cured after the hardening period prior to being gas-dried and stored for distribution.
Breeze blocks are a structurally sound and fire-resistant material suitable for construction. Concrete masonry units are widely used in the construction of foundation walls for buildings. Breeze blocks are available in two different grades, known as "N" and "S" grades. N-grade blocks are rated for use both above and below ground for both exterior and interior walls. S-grade blocks are subject to degradation from weather exposure and are rated only for above-grade use. S-grade blocks must be coated with a protectant to prevent weather damage when used in exterior walls.
Breeze blocks are manufactured in both standard and speciality form for sale to the construction industry by concrete suppliers. Homeowners in need of small quantities of breeze blocks can purchase them through big-box home improvement outlets, as well as from stone yards and landscape supply retailers.