Retaining Walls and Terraced Steps
The materials available for walls are many. The choice is yours. For low walls, of not more than two or three courses high, a light foundation of rubble tamped into thewill be adequate.
But more generally in terracing, the wall is to be built in loose ground and you will need to dig down to provide a foundation of at least three inches of concrete. With taller walls, you will need a foundation of up to six inches of concrete, again set in the soil rather than on it, for terracing.
Where the wall is to retain a large amount of soil or hold back a fairly extensive terrace, you will certainly need a double course. A cheap brick or breeze block can be faced with the better quality material. The cavities along the top of the double walls can either be capped or filled with some of the wide variety of plants suited to this type of situation.
Where you have to dig into the soil for foundations, you will also need to insert a damp course about 6 inches above soil level. Weep holes for drainage are vital, too, and should be left at intervals of about 6 feet along the base of the wall. To assist drainage oh the retained side, crocks or cinders should be placed in the soil close to the weep holes.
Dry walls are generally not suitable for retaining walls on steep slopes, unless you are a real professional at building them. But you could try your hand at a low one foror a slight terrace effect. Dry walls more than a foot high should be given a backward slant of about one inch to a foot in height.
Tiny peat walls can also be most attractive for a low terrace but getting hold of the blocks may be difficult in some areas. They look best in rural settings or a garden with a slightly ragged look.
With solid walls, which are most suitable for terracing, the main points to remember are the absolute necessity of maintaining line, level and plumb. Adequate mortar joints and the need for piers or other forms of support are also vital in long walls that have to retain a large amount of soil.
Line level and plumb are assured by regularly checking with string line, spirit level and plumb line.
For concrete blockwork, mortars made with ordinary cement and sand are too strong. Using slightly weaker mortar of masonry cement and builders’ sand — not concreting sand — in a one to five proportion will ensure that any cracks that may develop through settlement or temperature changes will follow the mortar line and will not crack the blocks. Then, you can re-point as necessary. Mortar joints should be made about f of an inch thick for blocks and the blocks should be laid to ‘bond’, with staggered vertical joints as with brickwork.
Steps in Terracing
Creating steps requires that extra bit of expertise at the best of times. And certainly in terracing they may present more problems than is normally the case. Quite often, the situation will call for steps from a fairly high drop and thus constructed in a way that they are entirely safe for those walking on them.
There are numerous materials available, but for a difficult site the choice is fairly restricted-cither completely flat-surfaced slabs or heavy timber. Concrete, of course, could be used but is so permanent that it is seldom recommended for steps.
From a high drop the steps should not be too steep; each step should have a few inches extra length than is normally the case and with extra long flights and curving ones, a regular ‘landing’ perhaps with a seat may be useful. The treads should not be less than about 16 inches, and the risers about six inches. When you start the construction job, do it from the bottom and work upwards.
Give some thought too to the wings of the steps particularly on hillside sites. These side walls can take a variety of attractive forms. You could use cavity walls for planting, peat walls, stone, or formal brickwork capped for finish. If you do decide on planting the walls lining your steps, do not use training plants which are likely to grow down to the steps themselves. Otherwise, you could have a nasty accident.