In a hollow concrete block wall you can lay a wider strip foundation on the downhill or outer side of the wall and set in it L-shaped steel rods on which you can slot the blocks for extra reinforcement , then fill in the block cavities with concrete.

A tall wall over about 1.2m (4ft) high must incorporate supporting columns called ‘piers’ at each end, and also at intermediate positions along its length if it’s very long. You may, though, just want to include piers in a smaller wall purely for visual effect, where the wall breaks at each side of a flight of steps, or where the wall must support a heavy gate.

In a brickwork wall you should bond the piers into the structure for strength but in solid block walls you can simply tie a stack-bonded pier to the wall by setting galvanised expanded metal mesh in the horizontal mortar joints.

A wall of hollow concrete blocks can be similarly tied to a matching pier with special metal cramps, and the hollow cavities can then be filled with concrete for extra rigidity.

Another means of reinforcing an earth-retaining wall is to build it thicker at its base, stepping back the courses from the earth side to the final thickness at the top.

Long walls must also incorporate breaks in the bond called ‘movement joints’, which allow for seasonal expansion and contraction. Joints should run the full height of the wall and can be packed with a compressible material such as expanded polystyrene which can then be pointed with a weak mortar mix to conceal the gap. You should leave movement joints at every 3.6m (12ft) in brick walls and at every 1 8m (6ft) in block walls

Further Readings:

• How to Build a Wood Retaining Wall
• How to Plant a Hedge, Climber and Wall Plants

You can provide drainage in two areas: at the back of the wall and actually through its face. To drain the back you can set pipes of porous, unglazed terracotta or plastic slightly sloping and surrounded by gravel to quicken the rate of drainage – behind the wall, just above the foundation. Take the pipe run along the wall to each end, where the rainwater can drain into a soakaway or other suitable drainage point.

To drain the retained bank through the wall you can simply leave weep holes’ – open mortarless joints every one metre (3ft) just above ground level, or set short lengths of 75mm (3in) diameter drainage pipe in the wall at these intervals, tilted slightly downwards to the outside.

In very wet areas, or where you’re building a high wall, you’d be wise to dig out the earth behind the wall and make an infill trench of well-rammed broken bricks topped with gravel. This will help to relieve the pressure on the wall from expansion as the soil soaks up water in winter.

Where there’s an excessive amount of water draining from your wall you should make a shallow gutter or gully at its base to carry the water to a suitable drainage point.

In addition to providing drainage for the bank you can further protect your wall from damp by applying two coats of bituminous paint to the back face, or by tacking on a sheet of thick 250 gauge polythene. Take care not to damage this membrane when you back-fill behind the wall.

It’s not usual to incorporate a damp-proof course (dpc) in a garden wall, but for greater protection from rising damp you can bed a layer of slate between courses, or lay a course of water-resistant engineering bricks at this point instead. If the wall adjoins the house, and rises above the house damp course level for any reason, a vertical dpc must be included between house and wall to prevent any moisture from rising into the house structure.

Finally, you should bed sound copings of concrete or brick on top of your wall, to keep water out of the mortar joints. Precast concrete copings usually have a bevelled top for drainage, project beyond the face of the wall, and have channels called ‘drip grooves’ under the front edge to prevent water trickling back onto the surface of the wall. You can also buy a variety of special coping bricks with shaped edges for a softer, decorative effect.

Further Readings:

• How to Build a Retaining Wall
• HOW TO BUILD A WOOD RETAINING WALL

Bricks must be dense and durable to withstand the damp conditions to which your wall will be exposed, and can give a neat, formal appearance in a garden that has rigidly defined areas, such as lawn, patio and rockery Choose special quality or special engineering bricks which are quite impervious and ideal in wet surroundings. Ordinary quality or common bricks are far too porous and susceptible to frost damage, although if your wall’s going to be fairly small and in a sheltered situation you can use the more attractive second-hand ordinaries in conjunction with a water-proofing treatment.

The strength of a brick wall is in its bonding and the mortar mix used. A brick retaining wall, therefore, must be built a minimum of 225mm (9in) or one whole brick thick in a tough bond such as Flemish, English, or English Garden Wall bond for strength.

Concrete blocks, which are much larger than bricks and much lighter to handle enable you to build a high wall relatively quickly. They’re available either solid or with hollow cavities to take reinforcement. Make sure you choose dense quality blocks that are suitable for use underground.

If you don’t like the plain, functional look of concrete blocks you can clad the completed wall with a cement render, or coat it with a textured masonry paint. A rendered finish, though, is likely to crack eventually in damp conditions. Alternatively you can just use the blocks underground and continue the wall above ground with bricks. Concrete blocks should be laid in stretcher bond to give the strongest structure.

Decorative concrete walling blocks are suitable for low retaining walls; they’re available both in brick size and in the larger 215×440mm (9×18in) size, and usually have a split-stone or riven face for a more natural, softer look. They also come in a range of reds, greens, and buff tones for a more attractive finish. You should only use this type of block above ground. Use the same bonding patterns as bricks for a stronger structure.

A cast concrete retaining wall is tough and durable, but it has a drab, slab-like appearance and calls for the construction of sturdy timber formwork to mould the mix while it hardens. If you think you’ll need such a robust structure you can make it look a little more attractive by adding a pigment to the mix

You can even build a dry stone retaining wall for an unobtrusive cottage-style garden wall, although it’s not suitable for holding high banks or heavy soil weights. The irregular soil-filled gaps between each stone make ideal places for introducing creeping plants to mellow the overall look of the wall. In this type of wall, each stone must be tilted downwards into the bank, forming a slanted or ‘battered’ wall. This will increase the strength of the structure, and will also give it a much less formal appearance.

Naturally rot-resistant hardwoods or preservative-treated timber can be used to make a wooden earth retaining wall, or you can use it as cladding for a concrete or blockwork wall. Railway sleepers, for instance, which you can often buy from specialist suppliers, can be used to make sturdy retaining walls if you pile them on top of each other, or stick them in the ground vertically, and support them with steel rods or stout fence posts set in concrete foundations. You could even stack concrete or wooden fence posts in this fashion, or in a dove-tailed design, to leave small soil-filled gaps between each post for planting.

Further Readings:

• How to Choose the Materials for Your Garden Walls and Fences
• How to Design a Family Garden

Building up to ground level

1. Start laying the first bricks at a corner if one is planned, at one end of the wall otherwise. Bed down the bricks in the outer ’skin’ first.

2. Having laid several bricks on each side of the corner, lay the first course of the inner ’skin’ alongside them. Note how the bond is arranged.

3. With the first course complete at the corner, check with a builders’ square that there is a perfect right angle inside and outside the corner.

4. Return to the corner, and start to lay the second course of brickwork in the outer skin, scraping off excess mortar with the side of the trowel.

5. After laying two or three courses of stretchers, lay the next course as headers – a bonding pattern known as English Garden Wall bond.

6. As you add each course to the wall, check that it is level, that the faces of the wall are truly vertical and that the corner is a true right angle.

7. When the footings reach ground level, form drainage holes in the wall by bedding short lengths of plastic waste pipe in a generous mortar bed.

8. Check that the pipe slopes down towards the outer face of the wall at a slight angle so that it will drain water away efficiently.

9. With the piece of pipe in place, you will have to cut the bricks in the inner and outer skin of the wall to maintain the bonding pattern.

10. Continue building up the wall above ground level, alternating three to five courses of stretchers with a course of headers.

11. As an alternative to building in short lengths of pipe to provide drainage, you can form weep holes -simple gaps left between the bricks.

12. Where you have left weep holes in the ground-level course, lay the next course as stretchers to bridge them and maintain the wall’s strength.

Completing the wall

1. Instead of English Garden Wall bond, you can use Flemish bond; each course has alternate stretchers and headers laid as shown.

2. When your wall has reached the height you want, finish it off with a soldier course – a course of bricks laid on edge to form a coping.

3. Since the top of the wall is the most exposed, ensure that a complete layer of mortar is chopped’ down between each of the soldiers.

4. Complete the soldier course by pointing neatly between the bricks. Rounded joints, formed with a piece of metal or hosepipe, look neatest.

5. Finish the job by brushing down all the wall surfaces with a soft brush to remove any excess mortar that could stain the brickwork.

6. Leave the wall to stand for a few days, then start to back-fill behind it, tamping the soil down gently but firmly as the level rises.

Further Readings:

• How to Design a Large Banked Garden
• How to Build a Stone Wall

When erecting a fence, make sure you treat all sawn surfaces with wood preservative, “cap” the posts and install 6-inch strips of lumber (gravel boards) to protect the base of the panels from water splash and rotting.

Wooden posts are usually made of tanalized softwood. Hardwoods such as green oak are available, but they are expensive, heavy to lift, and can twist and split if they are not cured properly. However, they are highly resistant to rot, long lasting, and have an attractive grain.

When buying posts, check they are suitable for the panels you have chosen??heavy-duty panels need large posts. It is very important to check the length of your posts before buying. For most purposes, 24 inches of the post is buried below ground level. If the ground is uneven or slightly sloping, or if you are on an exposed site, the posts need to be longer. Always buy posts that are longer than you think you need, particularly if the ground is sloping; it is easier to cut off extra length than to add to posts that are too short!

In heavier soils, tanalized softwood posts supporting a low wooden or wire fence will last about 15 years when knocked straight into the ground. Concrete posts look harsh and utilitarian. However, they can be painted and will last indefinitely. Climbers that are naturally self-clinging will attach themselves to fence panels, but be prepared to drill supports for others into the concrete posts. A system of concrete posts and gravel boards, with fencing panels slotted into preformed grooves in the posts, is easy to manage and will last for years, but it is somewhat municipal. When removing old panels and slotting in the new ones, make sure you ask your neighbors to remove their climbers first!

Setting posts in concrete provides stability, particularly in lighter soils, but there is a tendency for wood to rot at the junction between post and concrete unless it is thoroughly treated with preservative beforehand; removing a lump of concrete to replace the post is a nightmare! A good alternative is to raise the concrete a few inches above ground level and slope it away from the post to encourage water to drain away and reduce the likelihood of this happening. Ready-mixed fence-post concrete is available from building suppliers or hardware stores and is an excellent, if somewhat expensive, small-scale option.

Fencing spikes are useful in heavier soils and can be fixed in concrete for added stability in light soils. The posts are fitted into sockets, making them easy to replace.

1. Before doing any digging or hammering, check the location of services such as electricity and water.

2. Make a pilot hole with a crowbar or metal spike and sledgehammer, This is particularly important on stony soil as the spikes twist if they hit large stones or flints.

3. Insert the driving tool designed by the manufacturers to avoid damaging the socket. If you hit the spike itself, the sides of the socket will splay.

4. Use a sledgehammer to drive the spike into the ground with vertical blows. Check with a spirit level every few strikes to make sure the spike stays vertical.

5. Stop when the “box” is just above the ground and screw in the post.

Further Readings:

• How to Pour a Concrete Slab
• HOW TO REVIEW THE SITE IN COTTAGE GARDENING

- The “base” line for each panel is along the top of the posts rather than at ground level, so that the tops remain level whatever the slight irregularities in the ground. The tops of the posts are cut to length and treated with preservative once the fencing is completed. Avoid cutting the base of the posts because these have already been treated.

- If the ground is steeply sloping, your fencing needs to be stepped. Work out the height difference between the highest and lowest panel and ensure the “steps” are equally spaced. Do this by securing a taut horizontal line from the top of the slope to the bottom, attach it to a cane and measure the change in depth. Measure the horizontal line to work out how many panels and posts fit in that length. When making important mathematical calculations, it is worth getting somebody else to check them for you; answers may have to be modified! The most important factor is that the fence looks level to the eye, even if it isn’t.

- If you are using concrete to secure the posts, erect a run of panels first, holding them upright with hardcore and supporting them with battens, then make any final adjustments before adding the concrete-rather than making up the concrete in small batches,

- It is vital that the posts are vertical; check them constantly, holding a spirit level against each face in turn and adjusting as necessary while packing rubble around the post to hold it upright. It is possible to buy spirit levels specially designed for checking posts, with both vertical and horizontal levels, which are attached to the post with elastic bands.
Make sure the string marking the fence line is level with the center of each post and work out whether the boundary lies in front of or behind the line, otherwise life might get rather interesting!

- If the first post of your run of fencing is attached to a house wall or outbuilding, secure it with 1/4-inch diameter expanding coach bolts. Drill the central hole first and the two other holes equidistant from that. Check that the post is vertical using a spirit level, then make pilot holes at the relevant points with a masonry bit, marking the brickwork below. Drill the holes of the correct size through the wood and fit coach bolts into the wall. The bolt head must be countersunk into the wood so the first fence panel lies flush against the side of the post. If there is a gap between the wall and the post, because the wall or post are not vertical, pack it with wedges cut from slivers of wood that have been treated with preservative, or use plastic wedges. It can be a nuisance trying to get the positioning right, but it is vital that the first post is vertical otherwise there will be gaps in the fence.

Further Readings:

• How To Maintain Potted Herb Gardens
• How to Grow your Organic Flower Garden

Hedging subjects can now be planted at almost any time of the year as they are grown and sold in containers. It is generally a bad idea to try and establish a hedge during the summer as you will have all kinds of watering problems to contend with, apart from which the purchase of container grown hedging is inordinately expensive compared with that of bare rooted stock purchased during the dormant season. Deciduous hedging is best planted during the winter, but broadleaved evergreens and conifers should be left until the spring.

Select plants that are well furnished to the ground and go for the smaller sizes as these are more manageable and easier to get estab­lished. Large plants seem to provide an instant barrier, but unless you are excep­tionally lucky they will tend to have naked lower parts and rarely fill out to make an impenetrable hedge. Plant between 30 cm and 50 cm (1 ft and 1 ft 8 in) apart depend­ing upon the habit of the subject, where space allows in an alternate triangular fashion. Naturally the closer the plants are set the more quickly the hedge will become serviceable. If time is not a serious consider­ation a good hedge can be made much more economically by spacing plants further apart and feeding them well to encourage rapid growth. Once successfully estab­lished, a young hedge requires considerable attention if it is to be an object of beauty in future years. It is always a mistake to let plants grow tall too quickly. Encourage dense bottom growth by keeping them low initially, otherwise they become top-heavy and unwieldy and can only be rectified by drastic pruning.

Further Readings:

• How to Maintain a Small Garden
• How to Design a Formal Garden

A modest form of built-in decoration is a simple coping placed on the top of the wall, often used to complement fine stone or brick. More of a feature can be made if tiles or slate are used to complement the fabric of the wall. Piers or columns are a means of creating a functional but decorative structure: they may be there primarily to support the wall, but they are also ornamental and can be used to break the monotony of a flat surface. Another way of decorating a wall is to create a small round or square window, which can be left as an open space or covered with a metal grill. This will allow a glimpse of the area beyond, encouraging the observer to explore further, while from a distance the feature will look like a picture hanging on the wall.

Fixed patterns and designs using different coloured bricks can be incorporated into the wall at the time of building, and certain bricks can be left slightly proud of the wall surface to form a raised pattern. A less subtle form of decoration is to use pierced concrete blocks in a geometric pattern. These can be used on their own or built on top of an existing low wall, their angular appearance used as an asset in a suitable, linear design, or softened by climbing plants.

Applied decoration does not need pre-planning and can be used to add variety to existing walls. Urns, balls, obelisks and finials all look effective placed on the tops of walls, and framing columns or piers next to gates or doorways can be highly decorative. A more creative approach is to attach items to the wall. These can be in the form of ready-made pieces of sculpture, such as decorative masks, or perhaps a few unique pieces found in an antique shop. Another possibility is to make a mosaic out of fragments of coloured tiles and porcelain embedded in cement.

None of these effects should be overdone or allowed to become too dominant; they need to be subtle in order to blend in well with the garden.