Concrete Masonry Unit

A concrete masonry unit, commonly abbreviated CMU and often called a cinder block or concrete block, is a precast rectangular block of cast concrete, typically hollow-cored to reduce weight and material use, laid in mortar courses to build load-bearing and non-load-bearing walls. Standardized manufacturing developed through the early twentieth century made CMU a low-cost, fire-resistant, structurally reliable alternative to fired brick and stone masonry, and its hollow cores allow steel reinforcing bars and grout to be added for greater structural strength where needed. It became especially widespread in mid-twentieth-century commercial, institutional and utilitarian construction worldwide, valued for the speed and low skill required to lay it compared with finer masonry, and it remains a standard structural and foundation material today, often faced with a more finished material where appearance matters.