Concrete blocks are a cheaper and easier alternative to laying bricks. Solid concrete blocks are used for load bearing walls and are heavy to lift. The disadvantage is that they are less attractive than bricks and need to be rendered if used for an exterior wall, or if used for an interior wall, rendered and plastered. Dry lining, an alternative to plastering is also an option.
Alternatively, you can now buy faced building blocks with a stone textured or decorative and coloured facing, but they do tend to be more expensive.
If you are intending to insert support rods through a retaining wall, use concrete blocks with a cavity. There are two types of cavity block: one with a single cavity and another with two discontinuous cavities, which are also called cellular blocks.
The breeze block is made of cinder aggregate, is lighter than the concrete block and has some insulating properties. This type of block is generally used for building interior non-load bearing walls.
There are three types of stone block: cut, pitch faced or dressed and reconstituted.
As their name suggests, cut stone blocks have been cut into a block with all the sides dressed. This type of stone block is smooth on all sides and is therefore the most expensive.
Pitched faced (dressed) stone blocks have one rough face while the other sides are smooth allowing for neat mortar joints.
Reconstituted stone blocks are the least expensive as they are made of crushed stone, sand and cement which is moulded to look like natural stone.
Square concrete blocks that feature a decorative design that runs through or pierces the block are used to build garden screens. Screen blocks are not bonded in the same way as blocks are in standard construction, therefore supporting piers built of matching pilaster blocks (see below) are essential for the structural integrity of the screen wall.
Screen blocks should never be used to build load bearing walls, but they can support a lightweight structure similar to a carport roof built from timber and corrugated plastic sheets.
Pilaster blocks are used in conjunction with screen blocks. They will be the same size as the screen blocks and have a cavity through the middle so they can be placed over metal reinforcing rods. A recess or locating channel will be cut in one face or in two opposite faces (depending whether the pilaster block is located at the end of the wall or in between the ends) to house the screen block.
Thermal insulation blocks
These are lightweight concrete blocks that are thermally efficient with excellent insulation properties. Depending on the specification, thermal insulation blocks can be used for load bearing and non-load bearing walls.
Walls built of decorative glass blocks can provide a highly attractive and colourful feature. There is a range of colours available and a number of interesting effects such as marble, raindrops and cloud. Glass blocks are square and can be used for interior and exterior walls. Walls can be built exclusively of glass blocks or incorporated in conventional blockwork to create a more aesthetic design and to allow in more light.
Glass blocks are extremely difficult to cut and this should not be attempted. Half blocks are available to eliminate the need for cutting, as too are corner blocks for building walls with a right angle. A special mortar is required to lay glass bricks which will be available from your supplier.
Calculating how many to order
To calculate how many blocks you will need, divide the surface area of the wall you are building by the surface area of the face of one block. Sizes of block vary but a standard size for concrete blocks is 450mm x 225mm (18in x 9in).
The easiest way to cut a block is with a brick bolster and club hammer. Lightweight concrete or stone blocks can be cut with a stone saw. If you need to cut a block diagonally, use an angle grinder following a line marked on the block.