Bricks and blocks

Clay is the most common brick material. Commonly used is ‘fletton’ clay and the manufacturing method is ‘wire-cut’. Strong and durable. Some clay bricks are still made by hand.

Calcium silicate An alternative material (also called ‘sand lime’). Smoother and lighter in colour than clay. Concrete Moulded concrete bricks in a variety of colours and finishes available in some parts of the country.

Sizes and shapes

Standard rectangular bricks are 215mm (8!/2in.) long, 102.5mm (4in.) wide and 65mm (2’/2in.) deep. With a 10mm (3/sin.) mor-tar joint, this gives a ‘format’ size of 225mm x 112.5mm x 75mm (the metric size is slightly smaller than the old imperial size, but the difference can be accommodated in the mortar joint.)

Modular bricks are based on different format sizes: 300 x 100 x 100mm 300 x 100 x 75mm 200 x 100 x 100mm 200 x 100 x 75mm These will not fit with existing bricks and should be used only for free-standing walls. Solid bricks may have holes or have depressions (’frogs’) in one face. If the holes exceed 25% of the volume, the brick is known as ‘perforated’ (small holes) or ‘hollow’ (large holes).

Bricks and blocks are the basic building materials for houses. Bricks are generally used for the outer leaf of the cavity walls, load-bearing internal walls and for garden walls. Blocks, which are bigger, are used for the inner leaf of cavity walls, for garages for non load-bearing internal walls.

There are several different types of brick and block available — you need to know your way round the terminology to make the best choice.

Bricks are classified by their use and quality

Commons are used for internal walls or’ walls where they won’t show – they have a dull texture or poor colour. Commons are available in three qualities: ordinary for general use, interior for internal walls and special for use in exposed, damp or frosty conditions. The most common Common is the Fletton brick.

Facings are used where appearance is important – a wide range of textures and colours is available, often particular to certain areas. Hand-made facings are often very attractive. Faced bricks are commons with one to two presentable sides. Facings are available in ordinary and special qualities. Engineering bricks are heavy, strong and water-resistant. Their main use is for damp-proof courses, lining drains and sewers or very heavy walls. Generally only made in special quality. (Semiengineering bricks) are halfway between an engineering brick and a facing special.

Colours and textures

Most bricks are red in colour with a lightly-textured face. The name of a brick often indicates its colour and its origin – Leicester reds, Strafford blues, for example. Bricks from Kent and Essex are often yellow (’Kentish stocks’ for example); from chalky areas, often white.

Ranges of bricks are displayed in Building Centres. The London Centre has 800.

Buying bricks

Estimating For a singlethickness (102.5mm) brick wall, you’ll need about 60 bricks for each square metre; for a doublethickness (215mm) wall, allow 120 bricks a square metre. Allow 10% for wastage. Ordering The more bricks you buy, the cheaper they’ll be. Bricks are sold in 10s, 100s and 1000s as well as other amounts (packs of 350 or 700, for example, or a lorry-load of, say. 3000). Large loads should be delivered. Manufacturers will deliver lorry loads direct. Second-hand bricks Sometimes the only way of matching existing brickwork. Try demolition contractors.


Materials Most blocks are made from concrete, though hollow clay blocks are available in some areas for internal partition walls. Concrete blocks are either dense or lightweight (lightweight aggregate or aerated).

Sizes and shapes Most concrete blocks are rectangular and made to a format equivalent to six bricks (450 x 225mm), and 100mm (4in.) thick. Blocks are made in other sizes, including 75mm thick – the thickness of partition walls in many houses.

Clay blocks are made to a 300 x 225 x 100mm format though you can get other thicknesses. Types of block Like bricks, blocks come in different types for different uses.

For most jobs, lightweight blocks are preferable – they are easier to handle and to cut to size if necessary. Load-bearing and non-load-bearing grades are available. If used externally, lightweight blocks should be rendered or coated with a water-resistant finish. ‘Therma-lite’ is the most widely available brand of aerated block.

For damp conditions, choose dense concrete blocks which can be left unfinished or can be painted. Where appearance is important, use a facing grade of block (’reconstituted stone’).

For garden walls or carports, you could use hollow screen blocks – dense concrete with large pattern holes. Colours Most blocks are a very boring grey colour. Facing blocks come in more interesting colours and look like stone.