Cloddiau

Cloddiau is used here to refer to stone hedges which have the stonework set vertically on edge, and built in more or less even layers. As a method of construction it is particularly strong, as the stones wedge firmly together, as with the coping on a dry stone wall. However, cloddiau are quite different in structure from dry stone walls, as the stonework serves more as a protective skin to a relatively independent earth bank, rather than the face and hearting functioning as one structure, as in a dry stone wall. Cloddiau are much wider than standard dry stone walls.

Procedure

Dismantling

The basic process is similar to dismantling a dry stone wall. However, it is best to disturb the earth bank as little as possible, only cutting the face back 100-150mm (4-6″) more than the length of the building stones, to allow space for compacting the soil behind them. If both sides need repairing, it is best to dismantle and rebuild one face before dismantling the other. Much of the clawdd’s strength is reliant on the solidity of the earth core, and it is likely that no amount of manual compaction can make up for hundreds of years of natural settlement.

The stone is set out either in lines or piles of similarly sized stone, accurately graded to facilitate building. The width of cloddiau means that throughstones are very rare. However ‘bonders’, stones more than three times as long as they are high, are sometimes used, and if found, these should be set aside.

Batter

As with retaining walls, frames are not usually practical when rebuilding a clawdd, and line bars are used as described here. If a new clawdd is being built, a frame can be used, and should be set up as explained for free standing walls.

To increase their stability, cloddiau are not as steep-sided as dry stone walls. Put another way, cloddiau have a greater batter than dry stone walls, and the batter increases as the height of the clawdd increases, in order to maintain stability. Note, as in the diagram above, that a batter of 1:4 is ‘greater’, i.e. more sloping, than a batter of 1:6.

The diagram shows the minimum requirements for cloddiau. The standard clawdd has an minimum batter of 1:5, but may be more sloping, at 1:4. The high clawdd has a minimum batter of 1:4, but may be more sloping, at 1:3.

As cloddiau have a greater batter than dry stone walls, it can be difficult to maintain the batter and keep an even face to the stonework, without steps resulting. If the stones have rounded top corners this is less of a problem. With more regularly shaped stone you may need to tilt the stones slightly as shown in the diagram.

Another factor affecting batter is the length of stone available for building. If the building stone is not very long, that is, with a length less than twice as long as its height as laid in the wall, then a greater batter (about 1:4) is needed to maintain stability, even on a standard clawdd.

Medium stone, that is about twice length to height, can be used to build a standard clawdd at 1:5, or a high clawdd at 1:4. Unless the stones are very large, high clawdd should never be steeper than 1:5.

If the stone is long, or more than three times as long as it is high, then a smaller batter (about 1:6) is possible for a standard clawdd, which approaches the steepness of a dry stone wall.

Footings

Essentially the footings for a clawdd follow the same principles as for a free standing wall, bearing in mind the following:

1. When building a new clawdd, cut out the turf about 3-6″ (75-150mm) deep, and keeping it turf side up, put it aside to re-use for the clawdd capping.
2. Unless the stone is blocky, the footings should be set flat, even in a vertically coursed clawdd. If thin stones are set vertically in the footings the weight of the stone above will force them into the ground.
3. Unless the footing stone is over about 10″ (250mm) thick, it should be set below ground level.
4. When repairing a clawdd, it is normal practice to ‘trace’ any footing stones which would otherwise require considerable excavation of the bank. Whilst tracing is to be generally avoided, it is preferable to disturbing a stable bank. It is important that any traced footings are completely buried so that they cannot slip out of the wall.

Layering and grading

The largest stones are used at the base of the wall, with subsequent layers diminishing with height. The stones within each layer are of roughly similar size, forming distinct ‘courses’.

The key to coursing a clawdd is learning to use stones of somewhat varying size within a course, whilst retaining the identity of the course. Old cloddiau often have stones in the same course varying by about an inch, making a course that is gently undulating rather than absolutely even. However, adjacent stones must be as close in height as possible, avoiding the creation of steps, as building on top of any steps will be difficult.

The use of lines is crucial to coursing. They should be set to a height that accommodates the average size of the largest stones you have left, so each time you should move them up by a slightly smaller amount. Always set the line to fit the stones available, rather than setting the line to an arbitrary height and then trying to find stones to fit. The line is only a guide to the course and batter, and cannot be used to determine the exact size of stone. However, with experience stone selection becomes more accurate and the courses will become more even.

Placing the stones

Placing a building stone is similar to placing coping stone. Once the height of the stone has been selected there are four major considerations for each stone:

1. Always place the stone with its long axis into the wall. This rule is never broken.
2. The stone should fit tightly with its neighbours, to the side and below, with no large holes or gaps in the face. Some small gaps are inevitable, but the fewer there are the stronger the wall.
3. Contact must be stone to stone, with soil or turf no substitute for stone in the face of the clawdd.
4. The stone must sit on a firm base, and make a good surface to build on.

Awkwardly shaped stones, particularly those with a triangular shape, will need trimming to provide good faces and surfaces.

When placing a stone, make a small ramp of soil inside the wall, just beyond the point the building stones will reach. Set a stone vertically on the foundation so that its top meets, or nearly meets, the string line.

You may need to use a small amount of soil from your ramp alongside stones with rounder bases to ensure they don’t fall over.

Avoid getting too much soil on the previous course, as good stone to stone contact must be maintained, with the stone holding the earth, and not vice versa.

When learning, it is best to work sequentially along the course, placing one stone and then the next. Use stones of complementary shapes where possible, and keep the stones tight and vertical. It is tempting to slope a stone to get it to the right height, but this will create a weak point, and put out the pattern of coursing above.

With courses of vertically placed stones, some hedgers recommend putting a turf layer about 1″ (25mm) thick on each course, tamping it down well between the stones. The argument is that this makes a bed for the next course and ensures a quick growth of grass over the face to bind it. However, this technique is not generally recommended, as the outer edge of the turf layer can become eroded before any vegetation establishes, destabilising the face. Stone and turf faces are also more likely to settle unevenly, or more quickly, increasing the potential for collapse.

Keystones

Keystones are used about every 2′ (600mm) to ensure a tight finish. These stones are slightly narrower at the base than at the top, and are forced down into the course to tighten the stones in the section to either side. The distance between keystones depends on the stone size and type, but they should be placed so every stone is ‘squeezed’ by its nearest keystone. If the keystone is too narrow, or the gap between keystones too wide, some stones will not be ‘squeezed’ as the keystone is forced in.

When learning, use the following sequence to place keystones:

1. Select a suitable keystone for the height of the course.
2. Place as normal in the sequence, but alongside a stone with a good flat side.
3. Choose another flat sided stone to place beyond the keystone, with the flat side to the keystone.
4. Remove the keystone, and move the single stone slightly into the gap left by the keystone.
   
5. Continue the course to the next keystone.
6. Force the first keystone down into the gap left for it, squeezing the building stones.

The keystone will be of little use if its immediate neighbours are not flat sided. In effect the keystone is one in a set of three, differing only from the other two in being slightly wedge shaped.

Initially this process will be a matter of trial and error, but with experience you will be able to choose the right stones to give a tight fit.

Wedging

Either sometime during this process, or at the end of each course, you need to firmly wedge the ‘tails’ of the stones, below and between.

A good supply of wedges is not always present when building a clawdd, and if you run out, you will have to use soil, firmly compacted into all nooks and crannies using the end of a hammer handle. Take care not to dislodge the building stones.

Fill

As each course is completed, the middle is filled. For a new clawdd, try and use soil with large granules, or a soil and rubble mix. Very fine soils are difficult to compact. When rebuilding, you should only have the gap between the face stones and the existing bank to fill. As necessary, dig a ‘borrow pit’ in suitable soil to provide the fill.

The most important aspect of filling is proper compaction, which should be done every 6″ (150mm) of soil. You can compact the lower courses of fill by walking on it, and there are even stories of donkeys being used in the past for this task. Higher courses can be compacted with a ‘tamper’, or with the head of a lump-hammer, taking care not to displace any face stones. A bricklayer’s hammer can be used in the same way for compacting small and awkward gaps. You can test for sufficient compaction by pushing your index finger into the fill. It should be difficult to push it down beyond the first joint.

Where rubble is incorporated in the fill, this should be placed in alternate layers with the soil, and never more than one stone deep before soil is added and compacted. Don’t try and eke out the rubble to obtain an even distribution throughout the height of the wall, but use it in the lower layers, where there is the greatest weight to support. In some cloddiau the rubble is used more or less as a second skin, behind the face stones and essentially following the same principles for placement, but with less emphasis on coursing or keystones.

The weather plays an important role in compaction of fill. In wet weather it is impossible to compact the core without turning it into a muddy quagmire, and it’s not advisable to work in anything above a light drizzle. In summer the soil can be so dry that it fails to bind well under compaction, and if there is a water supply nearby, it’s a good idea to dampen the layer using a watering can with a sprinkler head.

Subsequent courses and joints

The process described above is repeated for subsequent courses, with the height of each subsequent course diminishing. Construction should follow the ‘waller’s prayer’ of ‘1 on 2 and 2 on 1′, and running joints should be avoided. However, where a step has developed in the preceding layer, it is almost impossible to avoid a two-stone running joint. Choose stones which will finish at the same height, so the joint can be crossed in the next course. Make sure it does not develop into a three-stone joint.

With experience, you can use a less sequential procedure for construction which allows for better coursing and crossing of joints. Use the line as a more accurate indication of height, placing the stones by best fit to the line, and positioning the larger stones in the dips left in the previous layer. This is easier to do randomly rather than sequentially. Eventually a number of clusters of stones will result, and you can jam a keystone into each gap to finish. It can be a far faster and more accurate method of coursing, but is not recommended for beginners. If you are not careful, you will end up with sections too long for keystones to squeeze sufficiently.

When leaving an unfinished clawdd overnight, make sure that its end slopes gradually enough that it won’t slump even if it rains.

Finishing and capping

Various methods are used for the last course or layer of a clawdd. Frequently this is simply the last course of the smallest stone, but sometimes a course of larger, blockier stones is added for increased stability. A less formal variation is to finish with irregular rubble left over from the rest of the building process. Another variation is to use longer stone, projected from the wall every metre or so to discourage stock from rubbing against the top course or scrambling over the wall.

Whatever the method used for the last course of stone, turf will normally be added to completely cap the wall and give it a level finish. Consequently the last stone course does not need to have a regular top, as any irregularities will be disguised by the turf.

The process of turfing the top of a clawdd is similar to making a turf dome, except generally only one layer of turf is used on top of a dome of soil. With new cloddiau an earth dome 12-18″ (300-450mm) high is added on top of the last course to increase the height of the wall, and to allow for settlement of the earth core. When repairing cloddiau with a relatively stable core, settlement should not be a problem, but additional soil can be added to create a domed top if extra height is needed.

Place a line of turf on top of the last course, positioning each turf carefully so that the roots are not exposed at the edge, and tamping each one into place, butted closely up against its neighbour. If new turves are cut they should be cut to a diamond or trapezoid profile to ensure that they bind well together. Once the tops of both faces are turfed, continue by turfing the middle section of the domed top.

If you run out of turves and it’s not possible to dig any more, it’s acceptable to leave the rest of the top bare, as it will vegetate in time. However, you must ensure that the fragile edge of the dome is covered, to protect it from erosion.

Rule (1974) identifies a ‘thatch’ of three rows of turf used in certain exposed parts of the Lizard Peninsula. One row on each side is placed earth down, then a row on the back of it is placed earth upwards. More earth is packed on and a final double row is placed which overlaps the other rows by about two thirds their width. Finally an earth cover is put on to finish. This method promotes quick binding of the turf.