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A stack of rectangular concrete blocks
8in.x8in.x16in. hollow-core CMUs in a basement wall prior to burial
HVAC shaft with 2 hour fire-resistance rating under construction at DuPont Canada, Mississauga, Ontario, 1986.
Head-of-Wall building joint.
"Cinder block" redirects here. For the American singer, see Cinder Block (musician).

In the United States, a concrete masonry unit (CMU) — also called concrete block, cement block or foundation block — is a large rectangular brick used in construction. Concrete blocks are made from cast concrete, i.e. Portland cement and aggregate, usually sand and fine gravel for high-density blocks. Lower density blocks may use industrial wastes as an aggregate. Those that use cinders (fly ash or bottom ash) are called cinder blocks in the US, breeze blocks (breeze is a synonym of ash)[1] in the UK and are also known as besser blocks or bricks in Australia. Clinker blocks use clinker as aggregate. In non-technical usage, the terms 'cinder block' and 'breeze block' are often generalized to cover all of these varieties. Lightweight blocks can also be produced using aerated concrete.


Sizes and structure

Concrete blocks may be produced with hollow centres to reduce weight or improve insulation. The use of blockwork allows structures to be built in the traditional masonry style with layers (or courses) of overlapping blocks. Blocks come in many sizes. In the US, the most common size is 8 in × 8 in × 16 in (20 cm × 20 cm × 41 cm); the actual size is usually about 3/8 in (1 cm) smaller to allow for mortar joints. In Ireland and the UK, blocks are usually 440 mm × 215 mm × 100 mm excluding mortar joints (approximately 17.3 in × 8.5 in × 3.9 in).


Concrete block, when reinforced with concrete columns and tie beams, is a very common building material for the load-bearing walls of buildings, in what is termed "concrete block structure" (CBS) construction. American suburban houses typically employ a concrete foundation and slab with a concrete block wall on the perimeter. Large buildings typically use copious amounts of concrete block; for even larger buildings, concrete block supplements steel I-beams. Tilt-wall construction, however, is replacing CBS for some large structures. The holes inside concrete block allow rebar and concrete (creating reinforced concrete) to run vertically through the block to compensate for the lack of tensile strength. Because most people find the appearance of concrete block to be drab and unattractive, exposed surfaces are generally given a decorative finish of stucco, brick, paint or siding. This makes glazed masonry an ideal fit for areas in which special attention must be paid to moisture issues and sanitation codes. This includes car washes, pools, locker rooms, shower stalls and dining areas such as cafeterias and commercial kitchens.

In the United States, concrete masonry standards are maintained by the National Concrete Masonry Association.

Breeze blocks are no longer used in the UK[2] because of their low compressive strength. Despite this, the term is still widely used to refer to concrete blocks more generally.


This gallery shows images of 200 series (190 x 190 x 390 full blocks) modular concrete blockwork used in residential construction in a cyclonic region of Northern Australia. Typically there is a vertical reinforced (N12 [1/2" or #4 U.S.] or N16 [5/8" or #5 U.S.] rebar) concrete core at every corner, alongside each opening and at 600mm (24") centers elsewhere. Bond beams (typically 2/N12 [1/2" or #4 U.S.] rebar) occur continuously around perimeter and over all openings and under windows. Corefill concrete is typically 15Mpa (2,200 psi) compressive strength. For more photos of similar construction see hurricane proof building.

See also


  1. ^ "breeze, n.3". The Oxford English Dictionary (2nd ed.). Oxford University Press. 1989. Retrieved 2007-11-30.  
  2. ^ "Blocks & Blockwork". University of the West of England, Faculty of the Built Environment. Retrieved 2007-11-30.  

External links

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