This section applies mainly to walls which run up and down slopes. Walls across slopes are considered here. Gravity has the advantage on slopes, and poorly built walls are prone to serious gapping and eventual collapse.

Dismantling

Particular care should be taken when dismantling walls on slopes to ensure that the section of wall uphill of where you are working is stable and not likely to collapse onto you during the dismantling or rebuilding process.

The process for dismantling walls on slopes differs slightly from that outlined for standard walls. Follow the principles here, adapting them as follows:

  1. Always dismantle the wall in a downhill direction, starting at the top of the section to be dismantled.
  2. Remove sufficient topstones to ensure the rest are stable, and not likely to slip and cause a cascade. The technique of roping the topstones for added security is described here.
  3. Remove the stones in layers, as for a standard wall, but note that the layers conform to the true horizontal, rather than running the length of the wall.
    Remove stones in layers
  4. Step the exposed end of the uphill section further back than you would for a standard wall, to ensure its stability.
  5. As you remove the stones, place them slightly uphill of the point from which they are taken. This is to counteract the tendency when working of only picking up stones which are uphill from your feet, which results in a shortage of stones at the top of the section and a surplus of stones at the bottom!

Direction of building

When building or rebuilding, start at the bottom of the slope and work upwards. This ensures that the stones are tightly butted together as you build.

Always build from the bottom of a slope

If you start at the top, no matter how carefully you place the stones they will tend to slide.

Stones will lside if the wall is built from the top of a slope

The easiest way to work is facing more or less uphill, choosing stones laid out to your side or just in front, which saves bending and back strain.

Use of wall heads

For added stability on slopes additional heads can be built into the wall to strengthen them, and to limit the extent of any gapping that does occur. Gaps are more of a problem on slopes than on the flat, both because the wall is subject to slippage, and because any gap which does form will tend to extend upward.

  1. When you build a head on a slope, it is most important that the head is structurally sound as its function is to support a considerable weight of stone. The fact that the head may be incorporated within a length of wall does not mean that any of the basic principles can be skimped, but rather the opposite. Use good runners and tie stones to bind the head to the wall on both the uphill and downhill side where possible, and carry the coping across the break
  2. Build a wall head at the base of a steep slope, or at a sharp upward break in slope. This head helps support the weight of the wall above it. Build the head after laying the foundations but before building the courses of the section uphill of the head.
  3. Where a wall runs up a steep hillside, the more heads the better. A head built every 22 yards (20m) may be appropriate.
    A dry stone wall running up a steep hillside
  4. To surmount a high outcrop, build the wall to a head against the bottom of the rock face. Start the wall again by building a head right on top of the outcrop, so there is no room for livestock to edge past.

Height and batter

On shallow slopes, the true vertical dimension of the wall is kept constant. The positions of the throughs and topstones are maintained at a constant height, measured vertically from the slope.

Keeping the true wall dimensions constant on a shallow slope

Batter frames or line bars should be used in the normal way, either in pairs, or set at a convenient distance from the existing wall or wall head. The lines are set horizontally.

Use batter frames in the normal way

Place the throughs as shown, so that each row forms a staggered line. Measuring the vertical height with a tape measure or marked stick should be sufficiently accurate, although a plumb bob knotted at the height of the throughs and the topstones will give a more precise measurement.

On steeper slopes, a problem occurs if the true vertical top height is maintained. The resulting reduced height, as measured perpendicular to the slope, can allow sheep to scramble over the wall. To prevent this, the wall may have to be built higher, in effect using the vertical top height to measure the distance perpendicular to the slope.

Keep the perpendicular height constant on steeper slopes

There are various ways of measuring to maintain correct height and batter.

  1. If using batter frames, it should be possible in theory to prop the frame perpendicular to the slope, which will give the required increased vertical height. In practice it’s difficult to prop the frame to the correct angle. Special frames can be made up for various angles of slope, but this is rather impractical.
  2. Line bars can be set up, either to the true vertical, or perpendicular to the slope, measured to the correct dimensions. This is probably the best method.
  3. A simple measured stick, held perpendicular to the slope, will give the correct heights, and the batter can be estimated by eye.

As the slope becomes steeper, the frames or line bars have to be set up closer together, in order to fit the horizontal lines. The lines can be anchored to the ground at the correct width with stones, but the frame or bars are still needed to give the batter and height.

Slope determines how close walling frames need to be

Some wallers set a line parallel to the slope, as an aid to grading the stone.

Foundations

Lay the stones on the true horizontal, whatever the slope. However large and heavy the stones, if set on a slope they are likely to slide, especially if they are slab-shaped. You can test this yourself by trying to shift a slab weighing about 1 cwt (50kg) on a flat surface. Try to shift it laterally. Then bed the same stone on a hard, sloping surface and see how easy it is to edge it downhill with a crowbar or other lever.

Follow these points to achieve level foundations:

  1. Dig a shallow trench along the line of the wall. Then to place each footing stone, dig out the trench a little more to make a step that is level both across and with the slope. Choose stones with flat bases. Opinion is divided as to whether the stones should be placed so they rest on each other, or independently. In practice the method chosen will depend on the degree of slope and the type of stone available. Thinner flat stone tends to be best overlapped, especially on steeper slopes. Larger and less regular stone is best placed independently, but closely butted together. Generally, the steeper the slope, the greater the need to overlap the stone.
    Foundation stones on a slope
  2. Check the bedding of large, flat slabs with a spirit level and board. Take care to get the first layer level, and then the rest should follow more or less naturally. With practice you should be able to align the stones by eye, but it’s always worth checking occasionally to make sure you are not being fooled by the slope, a problem which tends to occur more on shallow rather than steep slopes.
  3. On shallow slopes it is sometimes possible to taper the footings to form a series of ledges. The trench is still stepped to ensure that the foundation stones sit level, but each stone is slightly thinner that its predecessor, to form a ledge. Don’t carry this to extremes, using stones that are too thin to make adequate foundations.

Tapered footings on a shallow slope

Layering and grading

As with the footings, it is important that the stones are set to a true level, even though it is tempting on slight or moderate slopes to lay with the slope of the ground. Stones set with the slope are more likely to slide over each other, destabilising the wall during settlement.

Always lay stones horizontally

The layers of walls on slopes are different to those of walls on flat ground. On a slope, each layer starts with a footing stone at one end and finishes with a topstone at the other. Since the wall must be built wider at the hillside end of each layer than at the outer end, the guidelines, when viewed from above, should taper.

Differing layers on a sloping wall cause the sides to taper

Taking a vertical line up the wall, the stones grade from bottom to top just as in a wall on the flat.

Grade stones up the wall as on the flat

On shallower slopes you should work along a section of wall, placing stones to follow the true horizontal, rather than concentrating on building up one section. This helps ensure that you achieve an even distribution of the larger stones.

Take care to achieve the correct grading along and up the wall. Start at the footing and add the largest face stones, placing progressively smaller stones as you work outward along the layer. Keep the layer as horizontal as possible, which will mean doubling up the stones when you near the outer end.

Some wallers prefer to set their lines following the slope rather than to a true horizontal. This allows more accurate grading of the stone, by ensuring that along the wall, similar sized stones are used at similar heights relative to the ground. With this method of building you gain height and then length, rather than length and then height as in the horizontal method. Building for height and then length does have the disadvantage that it is more difficult to keep the stones tight. If using this method, it can be useful to also set a horizontal line to help in setting the stones level.

An alternative way to run the wall lines

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