18 months or so ago a form of walling revolution begun in the then Clwyd, as the replacement of dry stone walls, primarily along the A5, was begun. The chosen method was a new one - concrete panels with stone bedded into their face to give a dry stone look. Recessed mortar is visible between the stones although the joints have been subsequently reduced. The 'Clwyd Rockwall System' was born. In November 1995 an article "Facing Reality" appeared in "The New Civil Engineer" and subsequently a representative of Clwyd County Council gave an interesting talk at one of our Branch meetings.

Beauty is in the eye of the beholder and at the risk of being branded a heretic I don't think that some sections look that bad, not beautiful, but compared to some of the alternatives such as the contemporary mortared limestone work alongside the A5 immediately east of Betws y Coed, certainly not bad. At 50 m.p.h. I would have to concede that to the average motorist they probably do look like the real thing as was their designer's (David Buckland Clwyd County Council's group manager for bridges) intention.
[A5 Rockwall]

Left - Part of the A5 "Rockwall" retaining wall

One of the major justifications for their use is the damage to more traditional roadside walls through traffic vibration and salt spray. As an association we can harp on about the virtues of dry stone walls but it is always a stumbling block when it comes to trying to justify their longevity in the face of increased traffic levels and vibration it is almost impossible as our arguments cannot be quantified. In this respect we are always fighting a losing battle against engineers, they like concrete because they can calculate forces and stress loads, with dry stone work they cannot each stone is intrinsically unique and calculations can never be better than highly approximate.

This said a number of the arguments put forward in favour of the 'rockwall system' are highly specious and in themselves do not really 'face up to reality'.

I cannot refute the vibration argument but I do think it is far from being as simple as civil engineers would like us to think. For starters (theoretically) the degradation of dry stone work is exponential, i.e. once a waIl starts to show signs of collapse it does so at an ever increasing rate relative to time. The fact that many sections of the original wall were collapsing is probably at least part due to vibration, but that is the vibration of accumulated years of traffic in this case over about 160 years plus. Modern traffic levels are high but it is too convenient to assume that they alone are responsible for the collapse. It is unlikely that if walls were built now alongside the A5 they would last 160 years but equally the fact that they have really only fallen down in the last 5-10 years does not mean that walls built now would only last 5-10 years.

In fact many of the more recent repairs have only lasted 5-10 years, of course vibration is blamed. Other factors immediately spring to mind particularly the quality of work. We are always campaigning for better stonework and enforcement of quality control, few listen. Now when blatantly poor stonework fails it is not the wallers who are held responsible but the actual concept of dry stone work itself.

Another related factor in their collapse is the stone type and the method of construction. The stone used in the original work are mudstones and shales, and generally quite small at that. Examination of a number of collapses shows that many of the stones (too many) are "traced" i.e. placed with their longest axis running along the wall rather than into it or the bank. As any decently trained novice will know this is not exactly the strongest way of constructing a wall.

Beyond questioning the methods of original construction and more recent repairs it is also necessary to question the extent of more recent repairs. This is always a problem when dealing with contracting bodies. Experience shows that more often than not any visible degradation is only the tip of the iceberg. Perhaps not quite literally, it is not always the case that for every 1 m2 that the contracting body identifies as a problem requires another 9m2 of repair, sometimes it is and it is almost always more than just 1m2. If all the deteriorating wall is not stripped out and repaired, especially the foundations then the problem has only been treated it has not been cured, and continual treatment will be required if it is not going to collapse again in a very short period of time.

Salt spray is undoubtedly a problem with some walls and particularly in this instance where the rocks are laminates (i.e. built up in layers) and prone to damage. That is more the fault of the stone type than the fact that it is a dry stone wall.

This brings us into a tricky area as a Branch. We support a National policy of using local stone for walling works, but North Wales has a complex geology, not for us the vast tracts of land with a single rock type such as can be found in Derbyshire, Yorkshire or the Cotswolds. Very few of the stone types which constitute our walls are actively quarried, normally it is a choice of limestone, slate or granite, and then specific types not necessarily the same as those occurring in any given wall. In this instance it is possible to concede that in terms of deterioration (and size if a solid structure is to be achieved) the stone present is not ideally suitable for re-use. No similar stone is available locally. The stone in the rockwall panels is imported from England because it is highly durable, so why not import stone to build the wall, okay it will not be totally in keeping compared to local traditional walls, but compared to the rockwall panels.... Cost, maybe, that brings us to the thornier side of the "Facing Reality" article.

I hope I have shown that it is possible to question vibration and deterioration arguments even if they cannot be refuted. As such it is possible that the rockwall does have a roll to play. There are however more serious questions which can be raised as to their justification on productivity and cost. At the Branch meeting Clwyd's representative admitted that the article perhaps uses the best case scenario figures for the panels against the worst case figures for walls. The opening paragraph of the article reads:
"Traditional stone retaining walls built at the rate of 2m per hour. traffic disruption on adjacent busy roads minimised No skilled labour needed and total construct/on cost claimed to be less than half the going rate"

Hmm interesting... Much later in the article we discover that the panels are:
"…suitable for all retaining walls up to 1.5m high and claimed to be four times quicker than conventional masonry wall construct/on, needs no masons; no lorry loads of stone stockpiled along the route and crucially, significantly shorter lane closures."

And later still:
"Some 2.5km of wall is complete so far and total construction cost works out at around £1OO/m2. An average 70m stretch can be completed in a week ".

According to my calculations this means that dry stone retaining walls cost around £200/m2 and are built at the rate of 20-25m2 per week. I must be very, very rich.

I have just completed a roadside wall near Penmachno for The National Trust/Gwynedd Authority. This consisted of dry stone face with mortared core, 180m2 of single retaining wall, 80m2 of doubled retaining wall and 1 30m2 of doubled wall, (for ease of calculations and erring on the side of caution this would equate to about 450m2 of retaining wall) much of the work reached a height of over 2.1m. It took a team of 3 wallers backed up by labourers, scaffolding and plant hire sub contractors, 5 weeks. Long days were worked but a team of 4 wallers plus back up working normal days would have taken about the same time. So approximately 90m2 a week and at a cost of c.£55m2. Rates of pay were good for walling, graded according to DSWA Craftsman Certificate with for example Intermediate Certificate holders earning around £10/hour, and whilst I am not very, very rich l am more financially secure than at any previous time during my 10 years of self-employment.

Whilst direct comparisons are difficult, speed compares favourably and is of course determined by the number of people in the team - you employ the number of people needed to meet a deadline. The panels have to be placed sequentially, the length of wall you can work on is determined solely by the number of wallers. The Penmachno waIl did not include the cost of stone, but did include the cost of getting it to the site, it didn't include groundworks but did include the cost of materials for the mortar and its mixing, it also included the cost of scaffolding. Whatever the case it is almost impossible to come up with a scenario that could approach £150/m2 including stone and groundworks, let alone that being an average. Of course if you approach a large company that then subcontracts to a team of wallers or as often happens sub-contracts to someone who then sub-contracts the wallers, you could very easily get above £200/m2, but you shouldn't need to.

At the meeting we were told that there were not enough wallers around to do it any other way than through the panels. This just does not wash a team of 6 semi-competent wallers plus labour producing work of a reasonable quality should easily outstrip the panel team, and there would be no need to close any more of the road than for the panels. They close lOOm plus at a time, why would wallers need to close any more, you only need enough to keep just ahead of yourself moving the lane closure as you go. Similarly problems with stone storage usually come down to organisation and logistics, they do not need to become, or to be seen as, insurmountable. A larger team might need to close more of the road, but then the job would be finished sooner and hence overall closure would not be any greater. Clwyd, face reality.

In one respect Clwyd have probably faced reality, it can be difficult to get good wallers. For one off and smaller jobs it shouldn't be a problem, but to tackle every roadside wall it would be. Larger contracts tend to get sub-contracted and sub-contracted with inexperienced (if indeed they have any experience) wallers plucked from the dole. It is not surprising it can be costly and that the work falls down. It is a ludicrous way of approaching work. Amazingly Mr.Buckland is quoted in the article as saying "Correct stone placing is critical to the success of the entire operation". He is of course referring to the placing of stones in the concrete panels, yet these people cannot see that if walls are not built properly by good, experienced wallers, the walls fall down. It is always the concept of the wall itself that is blamed not the materials or the method of construction.

This is one of the more alarming aspects of mortared walling and the rockwall system. They persist because dry walls fall down often only because they were badly built. Good contractors struggle with continuity of work and the lack of large scale schemes to develop inexperienced wallers into good wallers, and so there are less competent wallers around. The whole system develops its own momentum as the need for and possibility of dry stone walling as an option is increasingly diminished.

The rockwall system probably does have a role to play in the right place. it is however worrying that when it is used on such a large scale it represents the thin end of a very large wedge. Much of the logic and rationale behind its use on the A5 seems to me to be ill-founded and highly misconceived not to say misleading. It already has an insidious nature. At the meeting we were informed that there were sections that had been done that possibly needn't have been, but it would have looked silly to have sections of dry stone wall interspersed amongst the panels. It would, but again it just means the chosen method builds up its own momentum, it is supposed to be a modern representation of an old tradition, but must replace the old because it no longer looks right. The lay-bys walls have also been replaced by rockwall panels. No problems of vibration and lane closure there, these were done we are told because it was convenient to use the panel team in this way during times when they couldn't work on the main highway. So now we are effectively getting walls replaced just 'because we can'. Very insidious.

There are many more arguments we could go into. Why not carry out routine on going maintenance to ensure longevity rather than spending millions on replacement? If the local stone can't be re-used and new stone has to be imported, why not provide a fillip to the North Wales slate industry? If panels are to be used why not use competent wallers to place the stones in the mould to give a complete dry stone effect? As the panels completely write off cars in heavy impact collisions what is their relative cost in terms of human lives going to be compared to more flexible and absorbent dry stone structures? There are many of these side issues, reality is not as clear cut as some people would make out.

Mr.Buckland it seems would like many other authorities to adopt his system. I firmly believe it does have a role to play, but I am concerned that it should be as a support to traditional methods and not become a panacea for all walling problems. The A5 wall restoration project could have been an opportunity to promote good dry stone walling. It could have provided for the development of good wallers. Whilst large scale wailing projects remain inaccessible to skilled craftsmen the future of good quality walling in North Wales will be continually compromised. As I observed in June 1995's "Opinion" -"Killing a Craft" a system which does not provide for continuity works against good craftsmanship, and many potential Master Craftsmen are lost to the craft. Is this and the Rockwall System the reality that people really want?