A footing provides a supporting base, and should be two to three times the width of the proposed wall. As a rough guide, the footing should be at least 10 cm wider on each edge than the thickness of the brickwork.

Method

1. Mark out the site of the foundations with string lines stretched between wooden pegs.
2. Dig a trench the length of the wall of the required depth: a half-brick wall (the width of a single brick) will need to be 38 cm (15 in) deep, whilst a full-brick wall, (two bricks wide) or a double wall with a space for planting cavities, will need to be 43 cm (17 in) deep. On heavy clay or in cold areas, you will need to increase the depth of the footing so that it is below the frost line.
3. Check that the base is level and the sides vertical.
4. Drive in pegs to the mark where the final level of concrete should be. Align with a spirit level and a length of wood spanning the pegs. The top of the footing should be at least 15 cm (6 in) below ground level to give adequate frost cover.
5. Soak the trench with water and allow it to drain. Then add 13cm (5in) of hardcore in the bottom and tamp it down.
6. Pour in 10 cm (4 in) of concrete (or 15 cm (6 in) for a full brick wall), slicing into the mix with a spade to work it in and dispel air bubbles.
7. Compact the concrete by tamping it down firmly with a length of timber, and ensure that it is level with the tops of the pegs. Leave the surface rough as a key for the mortar for the first course of bricks.
8. Allow the concrete to harden completely for a few days before laying the bricks or concrete blocks.