Blocks are constructed using concrete or cement. They may include a hollow core to make them lighted and to improve their insulation properties. They have been in use since the 1930s when they were commonly used for the inner leaf of cavity walls. At this point they were made from an aggregate of stone or industrial waste such as clinker or breeze, hence the term ‘breezeblock’.
A standard block is the equivalent of 3 bricks high and 2 long, the maximum size that one person can comfortably lift. They are available in a range of widths from 50 mm to 300 mm.
The kind of block selected for a particular application will depend on its:
- Load-bearing characteristics.
- Weight and handling properties.
- Thermal characteristics, such as U-value or thermal mass.
Dense blocks are usually made from cement, fine aggregate and course aggregate. They can be produced in a range of crushing strengths and tend to be used for structural purposes, such as foundations and load-bearing walls.
The advantage of lightweight blocks include their thermal insulation characteristics and ease of handling. During the last 80 years a variety of aggregates have been used - clinker blocks (8 parts clinker to 1 part cement), and blast furnace slag. They may be slightly more expensive than dense blocks
- Their closed cell structure means they have good resistance to water penetration.
- They provide good fire protection.
- They are easy to cut with a saw.
- They can accommodate fixings such as screws and nails.
For above ground uses, they might include mixes such as:
- cement : lime : sand 1 : 1 : 6
- cement : sand with plasticiser 1 : 6
- masonry cement : sand 1 : 5
- cement : lime : sand 1 : 2 : 9
Dense blocks are typically laid in mortars of average strength, 1:1:6 or 1:2:9. Stronger mortars may limit movement and may cause cracking of the blocks, although they are sometimes specified below ground level.
 Related articles on Designing Buildings Wiki
Featured articles and news
A quick introductory article about preliminaries in construction.
Brandenburg Gate - an historic structure that went from symbolising German partition to European unity.
A discussion between construction key players and leading insurers on the future outlook for construction insurance.
New guide from BSRIA on building performance evaluation in domestic buildings.
Rogers Stirk Harbour and Partners complete new trio of towers at Sydney Harbour.
With a new government consultation underway, ICE look at creating a smarter, more flexible energy system.
International Ethics Standards Coalition publishes first set of ethics principles for built environment professionals.
British Antarctic Survey announces research station is to relocate 23km due to growing crack in the ice shelf.
A great example of mimetic architecture with the Fish Building of India.
Could e-bikes be a solution to congested and polluted urban centres?
Government publishes details of £500bn investment pipeline in infrastructure, described as the 'most comprehensive ever'.