The Branch is gradually increasing its activities in attempting to help preserve these walls which in some forms are almost uniquely Welsh and in many respects more neglected and their construction more of a lost art, than dry stone walls.
Literally translated the Welsh "clawdd" (plural "cloddiau") means hedge, dyke or embankment. Sometimes it is mistakenly used to describe all walls, although almost without exception older wallers etc., use the term specifically refer to stone faced earth banks.
Cloddiau are akin to Cornish Hedges, that is a dry stone outer with a compacted earth (or earth/rubble core). The pattern of the stonework varies considerably from area to area largely dependant on the stone type used and to a lesser extent local traditions. This type of structure can be found in most walling areas, but most notably Devon and Cornwall and Welsh Coastal districts, and to a lesser extent in the North West of England.
Generally they are found in lower lying areas where stone is scarcer than the uplands. Examples can be found throughout North Wales but they are generally the exception rather than the rule except for Anglesey, the Bangor/Caernarfon coastal strip, and the Lleyn.
Very often they have (or have had) a hedge on top of them, occasionally a ditch is present to one side (probably where the earth core was originally dug, and serving to gain height on one side). However they are often bare on top and can be surprisingly low (frequently less than a metre high). Most of the areas where they are most common were cattle areas and hence there was less need for height in terms of stock proofing. If additional stock proofing was required dead wood or gorse would have been piled on top of their (normally) wide top.
They tend to have greater sloping sides compared to dry stone work, primarily to aid stability, particularly important with taller cloddiau where the weight of soil contained can be quite considerable. In some cases (the norm with Cornish Hedges, but rare in North Wales) taller cloddiau would have a concave face. This would aid stability at the base, whilst the relatively vertical slope higher up would add to stock-proofing.
Random built cloddiau are not uncommon. These are essentially dry stone walls with earth centres, and are particularly unstable if the stones are not laid with their longest axis into the wall. They are particularly common in areas where shale or similar rock, especially slabs are common. Something of a rarity are random cloddiau with vertically set stone, but they do exist.
In areas where large boulders are present the clawdd is often built random between the boulders until a relatively even height is achieved, and then finished off with courses of smaller vertical stone. A similar method is employed in areas where larger 'river stone' is utilised.
Another pattern, common elsewhere, but a rarity in North Wales is "herring bone". Here the stones are set in courses but are sloped rather than vertical. In any one course the stones slope the same way, but the slope is reversed on each subsequent course. Occasionally between each pair of alternating courses a course of stones is set flat (i.e. as in dry stone walling). Every now and then you might come across a wall where all the courses slope the same way.
Some very low cloddiau are built in panels. At regular intervals along the wall a single stone is set which runs from base to top of the wall, the clawdd is then built as normal for the area between these. The size of panel varies depending presumably on the availability of the dividing stones when it was originally constructed.
It is a common misconception that Cloddiau are built with turves in their face. This misconception is probably brought about by the proliferation of growth on roadside cloddiau, and the occasional field-wall. This growth is almost inevitably the consequence of colonisation and low grazing pressure over a long period of years (hence the growth on roadside walls, just pop into the grazed field to see the difference on the other side). When reconstructed with a proliferation of turves in the face there is a serious risk of collapse as the turves almost inevitably dry out and shrink.
One of the important aspects of cloddiau which is often forgotten, is their wildlife role. The earth core can be a haven for small mammals - more so than a dry stone wall - and in fact I came across a clawdd once where there was a slight difference in field level either side of the wall and it was absolutely riddled with badger holes. Insects can abound between the stones, and then there is the flora. Cloddiau are a far more suitable habitat for a wide range of plants because of the soil. Where there is a hedge it gets even better (everyone seems to know how important hedges are, a clawdd can just be a raised hedge minus the larger trees), and add a ditch with water and you have a mini nature reserve. Something in excess of 80% of all the recorded flowering plant species in Wales have actually been found on cloddiau, which given that the montane species haven't been recorded as there are few if any cloddiau above 1000', this is a truly remarkable figure.