Pierced-screen walling. Pierced-screen blocks are made of concrete and are open-work in the centre with a design of one sort or another. They are mortared together like bricks but because they are intended to create an overall open pattern, they are laid on top of one another with corresponding horizontal and vertical joints and not broken bonded like brick and stone. This means they do not have the strength of bonded bricks and stone, but for garden walling they are usually quite adequate. Because they are bigger than bricks and do not require bonding they are much easier for the amateur to lay, but they must be provided with a good foundation.
They can be erected to quite a height and are usually finished off with a precast concrete capping to tidy the job up and keep the weather out. Generally, unsupported runs need a pillar at each end and long stretches require intermediate pillars as well. Pre-formed concrete pillar blocks (pilasters) are available and are easy to erect, or the pillars can be made of toning or contrasting brick which can look very effective.
Pierced-screen blocks come in several shades and qualities. Some are very crude, but the better quality blocks are quite attractive. Moulds are also available, complete with instructions, for making the blocks at home — how satisfactory the results are largely depends on how good you are at this sort of thing and the raw materials you use for the job.
A section of pierced-screen walling incorporated into a solid brick wall can look quite pleasant and eliminates to some extent the shut-in feeling of high solid brick walls.
Because of the open nature of this kind of walling, the down-draughts experienced at the base of solid fences and walls are considerably reduced.
Pierced-screen walling is particularly useful for making certain recreational areas like patios more private without shutting them in entirely. Privacy is achieved as it is difficult to see through properly without actually peering through one of the holes, but behind such a screen you can get an impression of something beyond, and sun and air can penetrate to a certain extent. You also avoid the very claustrophobic feeling a solid wall or fence might induce.
Honeycomb walling. The function and effect of honeycomb walling is similar to that of pierced-screen walling but it is created with bricks, laid so that there is an open gap between the vertical joints, which leaves a hole between each brick in the course. The bricks are bonded in each course so that where there was a brick last time, there is a hole the next course up. These holes should not be too wide or it makes the wall weak. More skill is required to construct such a wall safely and effectively, though properly done it can be a very attractive feature.
Concrete blocks. This is a pretty austere material requiring almost the same skill and effort to erect as any other walling material, and the effect is so bleak that apart from cost it has little to commend it. Concrete blocks can be either solid or hollow – the hollow ones are slightly more useful in a garden as alpines can be planted into the holes in the top. Concrete blocks can of course be rendered and/or painted but this increases considerably the amount of maintenance work subsequently required and reduces the choice of plant you can grow up them, as you need to have regular access to the surface of the wall.
Hollow walls. These are constructed in exactly the same way as solid walls except they comprise two skins with a cavity in between, the purpose of this being that dwarf plants can be grown on the top of the wall. Hollow walls should be kept low so that you can see the plants better, but if you want a higher one, trailing varieties can be used. Hollow walls are also best used as internal divisions within a garden because of the temptation to children to walk along the top – if it is accessible to them – and trample all the plants down.
Foundations are needed as for any other type of wall and, especially with a dry wall, the earth should be replaced very firmly at the back of the structure as the work proceeds.