When you look around you will see that there are many different types and colours of bricks available. A visit to a large stockist or a browse through a catalogue will enable you to choose something suitable. For garden walls you will probably want to choose a ‘facing’ brick which has an attractive decorative face and colour. The alternative here is to use second-hand bricks.
All bricks are sold in one size — 225 X 112.5 x 75mm. This is a nominal size since a brick is in fact 10mm shorter on each dimension. The 10mm is a ‘built-in’ allowance for mortar joints. It is therefore easy to calculate the exact number of bricks needed for a project.
The V-shaped indentation present in many bricks is called the frog. Generally speaking, bricks are laid with the frog uppermost since this allows for the mortar to lie in the brick and so produce a stronger bond, although, in fact, the frog exists only as a result of the manufacturing process.
For general bricklaying the mortar is made from 1 part Portland cement to 1 part hydrated lime to 6 parts clean sand. Where a wall needs to be stronger to withstand the elements, a mix of 1 part Portland cement to 3 parts sand is used. This mix should also be used for brickwork below ground level. A small amount of liquid plasticiser added to the mix will make it more workable. Also available are dry mortar-mixes in handy-sized bags, and these are especially useful for smaller jobs. The materials are in exact quantities ready for mixing with, water. A 50kg bag is enough for 60-70 bricks.
However you make mortar, aim for a stiffish consistency — sloppy mortar will not support the weight of a brick. Mortar goes off in about an hour — less in hot weather — so only mix up small amounts at a time.
Every wall, whatever its height, must be built on firm, level foundations. Hard and fast rules about foundation depths are difficult to make since soil conditions vary; clay in particular is likely to cause seasonal movement so here a minimum foundation depth should be 900mm. If you find it difficult to analyse whether your soil is firm or weak then err on the cautious side and go deeper.
As a general guide for a small wall up to m high the following can be applied: For a 215mm thick wall (two skins of brick) lay 230 mm of concrete in a 500mm wide trench at least 500mm below ground level. For a half-brick wall (single skin of brick) lay 150mm of concrete in a 300mm wide trench, 350 to 400mm below ground level. The concrete for foundations should be a mix of 1 part cement to 5 parts ballast.
Preparing the site
Set out the site by putting up profile boards at each end of it and well back from the trench. Cut notches in the top edge of each board and stretch string lines between them to represent the thickness of the wall and the width of the trench. It makes life a lot easier if the length of the wall is built to exact brick dimensions — this minimises cutting.
Dig the trench and drive timber pegs into the bottom. The tops of the pegs must be at the proposed surface-level of the concrete and should therefore be made level with a timber straight-edge and a spirit-level. Lay the concrete, compact it thoroughly and allow it to harden for at least four days before starting to build the wall.
A wall relies on the way the bricks are bonded for its strength. The vertical joints between bricks in adjacent courses must not coincide either on the face of the wall or
across its thickness. There is a variety of possible bonds. A half-brick wall up to 1m high can be built in stretcher or open bond. You should bond in piers (328 x 215mm) at the ends of the wall and at a maximum of 1.8m centres. A 215mm wall can be built using either English or Flemish bond. Careful cutting is needed at junctions and corners to avoid continuous vertical joints through two or more courses of brick.
Having mixed up some mortar on a clean board close to where you intend laying the bricks, transfer some to the mortar board. Start at one end of the foundation trench and spread a 15mm thick layer of mortar on the concrete. The mortar should lie between the inner profile lines. The first course of bricks is the most critical as it governs the line and level of the whole wall.
Place the first brick on the mortar and check it is horizontal using the spirit-level. Next lay a second brick 1.5m or so away from the first and check that the two are level by laying the spirit-level on the straight-edge across them. If necessary, use the handle of the trowel to tap down ‘high’ points of the second brick until the bubble in the spirit-level shows horizontal. Complete the bottom row of bricks, buttering some mortar about 10mm thick on the end of each brick before laying it. Ensure that it is straight and level with the first two bricks. When you come to the second brick laid, you may have to reposition it but by this time you will have a length of horizontal brickwork to use as a datum.
Next build up the ends or corners of the brickwork to about six courses so that a stepped formation is reached. Use the gauge rod as a guide to the uniformity of vertical courses and also use the spirit-level as a check that the end of the wall and its outer or inner face is vertical. If the gauge rod increments coincide with the top of each brick all is well.
With the ends of the wall complete, the centre can be bricked in. Attach the string line and pins into the joints at each end of the second course and use this as the guide to placing the bricks. Transfer the line to the course above as work proceeds. On a long wall the line may tend to sag in the centre. If so, a small metal device called a tingle can be used to support the line in the centre.
Spread the mortar along three or four bricks in the previous course at a time and more on to one end of each brick before it is laid. On a hot day in particular it pays to dip each brick in water before it is laid to make the mortar stick. As each brick is laid and tapped down, surplus mortar will squelch from beneath it. Remove this straight away by drawing the edge of the trowel along the bottom edge. When a course of bricks is complete, shape the joints using a pointing trowel or draw a small rounded piece of metal through the mortar to give it a concave appearance. An old bucket handle is handy for this or you can buy an inexpensive tool designed for the job.
Where a corner is reached the return wall can be treated as an entirely separate construction. Just check that the corners are truly horizontal and vertical.
If you have chosen a bond that necessitates cutting a brick then do so as follows. First mark the line of the cut with chalk. Use a sharp brick-bolster and club hammer to cut a groove on all faces of the brick. Place the brick on a smooth bed of sand and place the edge of the bolster in the groove. A single sharp tap from the hammer on the bolster handle should result in a clean cut.