What is it?
Blockwork refers to walls constructed using concrete blocks, sometimes called concrete masonry units. Concrete blocks are similar in form to bricks but are larger and made from cement, aggregate and water rather than fired clay.
Blocks are typically 440 mm long and 215 mm high, and come in a range of widths depending on the required wall thickness. They are laid in horizontal courses by a bricklayer and bonded together with mortar to form a wall.
Their modular size aligns with standard brick dimensions, allowing blockwork and brickwork to be used together in masonry construction. A concrete block is approximately the equivalent of two bricks in length and three bricks in height, allowing the two materials to align within the same wall system.
- 1Brick
- 2Blockwork
- 3Cavity Closer
- 4Blockwork / Engineering Brick
What does it do?
Like brickwork, blockwork can be used for both structural and non-structural walls.
Concrete blocks are generally cheaper than bricks, and their larger size allows bricklayers to construct walls more quickly, reducing labour time on site. Because blocks are usually considered less visually attractive than brickwork, they are often used in parts of the building that will be hidden or finished with another material.
In masonry cavity walls, blockwork is typically used for the inner leaf of the wall, while brickwork forms the visible outer face.
In industrial buildings, or in situations where brickwork would be too expensive, blockwork may also be used as the visible external wall.
Structural
Blockwork can be used as a loadbearing wall, transferring loads from floors and roofs down to the foundations. It is commonly used for internal structural walls or the inner leaf of cavity wall construction.
Dense concrete blocks can also be suitable for below-ground construction, depending on the block type and the waterproofing strategy.
Non-structural
Blockwork may also be used for non-loadbearing walls, such as internal partitions.
Because of its density and thickness, blockwork can provide good fire resistance and acoustic separation, making it suitable for walls between rooms or between apartments. It can also provide improved security compared to lightweight stud partitions.
Where is it used?
Blockwork is commonly used in several parts of a building where a strong, durable wall is required but the surface will either be hidden or finished with another material.
Typical locations include:
In some industrial or utilitarian buildings, blockwork may also be used as the visible external wall finish.
| Inner leaf of cavity walls | Where brickwork forms the external face |
| Internal loadbearing walls | Supporting floors and roofs |
| Internal partitions | Where fire resistance or acoustic separation is needed |
| Party walls | Between apartments or adjoining buildings |
| Service risers and cores | Vertical shafts for services |
| Basement or below-ground walls | Depending on block type and waterproofing strategy |
Types
Concrete blocks are manufactured in different densities and strengths depending on their intended use.
Dense block
Heavier and stronger, used for structural walls and below-ground work such as foundations and footings, or wherever higher strength or better acoustic performance is required.
Lightweight block
Contains lighter aggregates, making it easier to handle and cut on site. Provides better thermal performance but lower structural strength than dense block.
Typical sizes
Concrete blocks are commonly manufactured to the following modular dimensions:
Length: 440 mm
Height: 215 mm
They are available in a range of widths depending on the wall construction, commonly including:
100 mm
140 mm
190 mm
215 mm
These dimensions allow blockwork to align with standard brick coursing, enabling block and brick masonry to be used together in cavity wall construction.
How to specify
When selecting blockwork for a project, several factors must be considered.
Structural performance
A Structural Engineer will advise on the strength and thickness of blockwork required to support the loads from floors, roofs and other structural elements. They may also consider the weight of the wall itself to ensure the supporting structure beneath is adequate.
Fire strategy
A Fire Consultant or Building Control Officer may advise on the fire resistance required for walls. This is typically expressed as a fire rating in minutes (for example 30, 60, 90 or 120 minutes).
Acoustic performance
An acoustic consultant may advise on the sound insulation required for walls, particularly in residential buildings such as apartments. This may influence the density or thickness of blockwork used.
Wall build-up
Blockwork is often used as part of a larger wall assembly, such as the inner leaf of a cavity wall. The specification may need to coordinate with other elements such as insulation, wall ties and internal linings.
Other considerations
Large panels of blockwork may require windposts to provide lateral stability.
When used as an internal leaf in a brick and block wall, the blockwork needs to be finished with either render or an internal lining to provide a presentable finish. Internal linings require more space but also provide a space for sockets, switches and cabling to be routed.
Any openings in the wall, such as those for doors and windows, should be provided with lintels to support them.