Types of Wall

Retaining walls are those designed to 'hold back' a bank of earth, usually a terrace or steep slope of ground. However, low retaining walls can also be constructed to provide raised planting beds. Boundary walls mark out the limits of your property, provide security and privacy but also form a solid background to trees and shrubs and support for climbing and rambling plants.

Many gardens also have dividing walls, forming a break between areas of lawn and a patio or vegetable garden, for example. Dividing walls are a great way of providing visual interest in featureless gardens and are a good way to create 'rooms' in the garden. They need not be high: a dividing wall of say 750mm (2ft bin) in height is easy to build and is a good structure on which to practice your building techniques.

Walls can be constructed from brick, stone or concrete blocks, or even concrete poured on site - although this is normally used to make strong retaining walls within gardens. Different walling materials are used in different ways, and the thickness of them will depend on their height. The thickness of a wall will also determine the number and spacing of piers and buttresses that are built to support the wall. You can avoid building piers and buttresses if you stagger a wall in a zigzagging manner, while curving or 'serpentine' walls - also called 'cringle-crangle' - will support themselves, although they will take up much more space.

Safety Tips

• If you hire a concrete mixer, read the safety advice supplied with it. Never put your hands inside the drum while the machine is switched on, don't lean over it to look inside and wear safety goggles to prevent any loose specks from irritating your eyes.
• It can be a good idea to wear protective gloves when working with concrete, as it can irritate the skin.

Capping Walls

The way you finish - or 'cap' - a wall will make an enormous difference to its final appearance. Stone walls often have a traditional capping, depending on the region, while concrete blocks - now available in a variety of attractive sizes and finishes - can be finished with concrete slabs or even brick. Concrete has suffered a great deal of bad press in the recent past; we associate it too much with grim inner city tower blocks instead of looking at its great design potentials.

Concrete is in fact available in a range of colours and textures from the dull, grey aggregate finish of the early material, to colours matching local brick and stone, or brightly rendered or painted. You could even tile over concrete with mosaic tiles or brightly coloured broken shards of pottery. Different regions also produce different local stone - or bricks - crushed and used as the aggregate in the composition of reconstituted stone blocks. These, and concrete blocks, are considerably larger than bricks so building a wall is much faster - and cheaper - than using bricks or stones. But, whatever material you use, the finished wall will only be as sturdy and attractive as you build it.

Scale, Texture & Pattern

Consideration of these factors at the planning stage will help you make some decisions as to the type of wall you want. Open-screen walling units, available in a range of patterns and materials - including precast concrete and terracotta units - are useful for piercing solid walls and adding a decorative element. These pierced units are also useful as wind baffles - slowing down the wind over large areas - rather than creating a barrier that causes wind resistance.

The shape of most of our gardens tends to be regular - mostly a long narrow strip at the rear of the house and possibly a small square at the front. The most common mistake is surrounding a regular site with some structure that emphasizes this regularity. The simplest way to provide relief to the visual monotony of a site is to vary the materials used. Use brick or stone nearest to your house, and perhaps timber or concrete blocks for the rest. Alternatively, use one material, but vary the height of the wall at different points along its length.

Useful Tips - Brick Walls

• Whatever materials you decide to use, the basic techniques for laying stone, brick or concrete blocks remain the same. If you have had experience of laying bricks and pointing then you should find the process straight-forward. If, however, you need a high wall, or one that is complicated in design and function in any way, then it's probably best to hire a professional to do the job for you.
• Whatever wall you build, it will require solid foundations: generally, the depth of the foundations will depend on the height of the finished wall, the type of soil - especially if there is a high moisture content present, such as in clay soils - and the level at which frost occurs or the movement of ground moisture. In most cases, a depth of 600mm (2ft) will be sufficient, but if there are difficult site conditions, it's best to seek expert advice.
• When digging a trench for foundations, make sure you avoid any tree roots or drainpipes. Avoid ground that has recently been filled in, which will be too loosely packed, and make sure the soil is well drained or you may get subsidence. If the trench fills with water while you are digging, it's time to call in professional advice.