Although Cornish hedges, like cloddiau, have an earth core, in dimension and structure they are more like dry stone walls. Rather than being an earth bank with a stone skin, the stonework and earth core of a Cornish hedge make an integral structure.
The standard stone hedge design specified for roadside work by the County of Cornwall is shown below. Farm hedges are frequently higher than this, being 6′ (1.8m) or more where they border a track worn below field level. Whatever the size, the general principle is that the width of the hedge at its base should equal its height.
Procedure
Construction of a Cornish hedge is essentially the same as building a retaining wall, with a few minor differences relating to the concave batter, placement of stones and earth fill. When repairing or rebuilding a Cornish hedge you normally have to take down the earth core at least to the half way height, because the earth core is narrow and unstable without the supporting stones. The lower part of the earth core is best left undisturbed if possible.
Batter
Erect a batter frame or ‘pattern’ just beyond the end of the section. Alternatively use a frame which you can hold up against the side of the hedge from time to time.
Not all Cornish hedges have a concave batter, although it is by far the most common shape for walls in the area, dry stone walls and cloddiau type structures included. With a concave batter the hedge, as it settles, remains slightly concave or straightens out. With a straight batter the hedge may belly out and become weak as it settles. Another supposed theory for the concave batter is that it creates less wind turbulence, and thereby improves the shelter value.
Lines are raised at intervals of around 12″ (300mm) as for dry stone walling, although when you are first learning it is best to raise them in smaller increments, about corresponding to each layer, otherwise you are likely to lose the correct curve for the batter.
Placing stones
The basic principles for dry stone walling apply also to Cornish hedges. It is particularly important for the strength of the hedge to lay stones with their long edges into the wall. However, a major difference is that stones are placed to that they tilt slightly down and into the wall, opposite to the normal method for dry stone walling. One possible theory is that this directs rain water into the bank and promotes a better growth of plants. It is more likely that the stones are tilted to help achieve the correct batter.
The first three courses are tilted strongly down into the hedge, while succeeding courses are brought gradually up so that the top layers have their faces nearly perpendicular, as shown in the diagram. A rule of thumb is to have about 3″ (75mm) of batter in the first 1′ (300mm) of hedge height, and to decrease this progressively to perpendicular at the top. Follow the batter frame closely.
Fill
Menneer (1994) suggests that the only correct material for the fill is ‘rab’, which is a soft clayey or gritty shale, or sometimes decomposed granite, used as precursor to tarmacadam in road surfacing. In practice, as with cloddiau, any soil that combines well when compacted will suffice.
As with cloddiau, the earth packing is brought slightly above the level of each course so that the next course is adequately supported. Generally the rule that ‘stones hold the earth and not vice versa’ is followed, but some Cornish hedgers pack a layer of soil on top of the stones to help bed in the next course.
Finishing and capping
There are various ways to finish off the hedge. In the County of Cornwall specifications, the stonework is brought to within 1’6″ (450mm) of the proposed hedge top, above which are placed two rows of small stones. If granite they may either be finished (trimmed) or random (rough). If the top two rows are slate they are built in herringbone, to use up the small pieces split from the ‘raisers’ or face stones during construction. Herringbone also provides a good rooting medium for plants.
Once the stonework has been built to the full height, the earth core is finished to a well packed rounded profile, and then the turf is laid. Alternatively, a single or double staggered row of young hawthorn, beech or other hedge shrubs can be planted on top, and then the turf laid upside down around the plants. The turf will help protect the earth bank from eroding, whilst not encouraging grassy growth which would severely compete with the young shrubs for water and nutrients. Keep the shrubs weeded and watered until they have established. Details are given in Hedging – Planning a new hedge.
Other patterns
Chip and block
In Cornwall, the emphasis is on building horizontal courses in a neat masonry-block appearance, especially when using trimmed stone. However, the more regular the stone, the more poorly it binds, and trimmed granite hedges have a tendency to collapse outward or inward as the bank settles.
A method that is preferred in Devon is to build in the ‘chip and block’ style, where large ‘blocks’ and small ‘chips’ are used together. Although the stones are roughly graded from biggest at the bottom to smallest at the top, there is a mixture of chips and blocks within each course. The chips are used to wedge the blocks from behind so that they sit well and bond with the earth packing. The blocks are trimmed of any awkward projecting noses or inside corners which would otherwise keep them from tightening as they settle.
Some hedgers frown on this style, believing that the hedge can become unstable if the wedges shift as the hedge settles. The contrary argument is that the use of stone wedges rather than soil minimises settlement, and there is no problem as long as the wall is well built in the first place. The use of wedges on the face of the hedge is avoided by all hedgers.
Vertical random
Vertical random is usually associated with larger slates and some other fissile stone.
When building this style with non-fissile stone it is usually necessary to trim off any rounded ends to that the stones above will sit securely. With very fissile material you can usually tap the stones down securely without any shaping. Vertical joints are unavoidable, so instead you must break the horizontal joints as shown.
Other styles
Some cloddiau are built like a dry stone wall at the base, using stone not suited to horizontal coursing. Build random stonework to a reasonably consistent height along the length of the clawdd, levelling it out with the first course of vertically placed stonework.
A variation used in areas with large boulders is to build the clawdd with random walling between the boulders until a relatively even height is achieved, and then finish off with courses of smaller vertically placed stone.
Herringbone pattern is used in some parts of North Cornwall, the Devon coast and parts of Exmoor, where slate, level bedded sandstone or other fissile rock is common.
This method is particularly strong as the slates bind together well, and it is impossible to build a running vertical joint.
Occasionally a course of stones is set flat between each pair of alternating courses.
Rarely, you may find a wall with all the courses sloping the same way.
‘Shiners’, or large stones set vertically on edge and traced can be found in many areas, and are particularly striking in some of Dartmoor’s hedges. Although these break the normal rules of walling, they are stable because they have a good batter and are well tied in by other stones along their tops. This practice is explained in more detail here.
At Culloden battlefield near Inverness, the National Trust for Scotland have reconstructed a turf dyke thought to be similar to the boundaries which would have existed in 1746. The Leanach turf dyke, named after the area, has 12-14″ (300-360mm) of stonework, with a stone only fill, topped by turf. The overall height and top width are each 39″ (1m), with a base width of 4′ (1.2m).
The Highland Vernacular Building Trust in Newtonmore have done a similar reconstruction, creating a bank 36″ (900mm) wide at the base, and 28″ (700mm) wide at the top, 44″ (1.1m) high, including a 8″ (200mm) dome. The bank has three layers of stone sandwiched with turf, topped with turf alone.
