Laying Reclaimed Setts

For various reasons, there is a fairly steady flow of clients looking to re-create what they imagine to be a 'traditional' sett pavement. Some clients have old properties and want an authentic looking driveway or forecourt, while some locations have listed status and the relevant authority, be it an architect or a Building Control Officer, wants sett paving, and wants it laid as it would have been 100 or 200 years ago. And this is where the problems start.

Because so few people are now trained as streetmasons or mason paviors, the old skills are rapidly disappearing, and since the Second World War, we've seen a growing reliance on cement-based construction for sett pavements, with highly variable results. The supposed strength and adhesion of cement mortars and concretes, it was hoped, would make up for the lack of time-proven, genuine skills from the laying operatives. The result was a disastrous period of around 30-40 years when sett pavements failed on a massive scale because the old understanding of how a sett pavement works and how to get the best from the various materials had been superseded by an over-reliance on “modern” techniques.

The publication of the SCOTS report at the turn of the millennium and the subsequent work on BS7533 Parts 7 and 12 , covering sett laying and jointing have done much to improve the situation, and it is now possible to construct attractive, functional and reliable sett pavements using modern materials, but these new standards are not always suitable for specialist heritage projects, or the accurate re-creation of traditional sett pavements.

Let's look at a typical 'reconstructed' traditional sett pavement and an actual, as-it-was-when-laid sett pavement and see if there are any obvious differences.

• 1 - it minimises the amount of jointing material required.
• 2 - it makes for a smoother, less humpetty-bumpetty passage for both vehicles and pedestrians

With regard to the jointing material, this was often a matter of economics rather than structural benefit. The stone for the setts or cobbles more often than not came from a (reasonably) local source and so wasn't overly expensive or hard to obtain. However, the jointing would often need to be sourced from farther afield and could, in some cases, cost more than the stone for the setts. Lime, for the occasional mortared joints would have to be brought from a limestone region of the country where the raw material was crushed and fired and slaked to make a usable product, while pitch, a more popular option due to its flexibility and inherent ability to re-seal itself, had to be brought from overseas (The West Indies was a popular source).

For lower grade pavements, a crushed rock or splitt might be used, which was obviously cheaper than pitch or lime, but in such cases, keeping the joints 'tight' ensured better vertical interlock of the splitt/grit between adjacent setts and therefore of more structurally competent pavement.

So, whatever the jointing, the key was to keep it to a minimum.

Returning to visual differences between genuinely old pavements and re-constructed settwork using reclaimed materials, another important difference is the gauging. The width of a course of setts is referred to as the gauge. Setts of various widths need to be sorted to ensure each course comprises setts of a specific width or gauge which in turn helps ensure joint width can be kept to a minimum.

New setts, especially those with hewn surfaces, often have a permitted tolerance of ±15mm, which can result in as difference of as much as 30mm between individual units. Consequently, pre-sorting of setts and cubes into carefully gauged widths reduces the tolerance of each course and so ensure tighter jointing. However, all that pre-sorting involves a good deal of labour, and so the overall construction cost is increased. In the end it comes to a trade off between quality of work and job cost.

Almost invariably, there will be an edge course of longitudinally-laid setts to every sett pavement, regardless of where in the country it might be, or which materials were used in its construction.

Lanes, ginnels, alleys and other narrow access ways were very often laid with a prominent camber . This was almost always done to improve drainage, sending surface water the aforementioned edge channels, but there are instances where despite more than adequate endfall, a camber has been included.

The amount of camber is usually pretty moderate, so that even at the steepest part of the curve (nearest the channel edges) the crossfall is rarely more than 1:80 (1.25%). On a 2.4m wide pavement, the centre would typically be just 20-30mm higher than the edges, while on a 4.5m full width roadway, an elevation of 60mm or so in the centre would be typical.

This was partly covered in the discussion regarding joint width , but traditional sett pavements, which for convenience we'll define as those constructed prior to WWII, were almost never jointed with a cement mortar. There are one or two exceptions, but they really are rare. Reliable cement mortars only became widely available in the early 20th century and their use for jointing sett pavements didn't come about until the post-war construction boom when cement was seen as the cure-all for any construction project.

When good quality reclaimed setts are well laid and then carefully jointed with a genuine sett-jointing pitch, it can be a real thing of wonder. The jet black colouring of the pitch tricks the eye into ignoring its presence and, instead, your focus falls on the stone, which is where the real beauty lies.

Pitch is self-healing, so any minor movement is accommodated and, when the summer warmth returns, the pitch re-seals itself. It's also sufficiently durable to withstand regular pressure washing, so the 'good as new' look is easy to maintain.

In these days when any stone, from any part of the world is readily available at short notice and keen prices, it is easy to forget that, when those original sett pavements were constructed 100 years or more ago, they very largely relied on local stone. The concept of hauling stone any further than was absolutely necessary was viewed as a nonsense, and so we see gritstone and yorkstone setts in the northern counties of England, while granite is the medium of choice in Scotland and Cornwall.

There are some exceptions. Much of the granite seen as setts and kerbs in Liverpool and south Lancashire orginally came from the Wicklow Mountains 120 miles across the sea in Ireland. However, there was method in the madness. With no coal resources of its own, Ireland, and Dublin in particular, was reliant on imports from the Lancashire coalfield, and rather than send back empty ships, the holds could be stuffed with granite paving units as a form of merchantable 'ballast'.

The only source of granite in the English midlands, and for the south-east, is Mountsorrel in Leicestershire, so we see its distinctive red form on many highways and by-ways of English towns of those regions, while the much softer but more readily available limestone setts from the southern Peak District are rarely seen more than 20-30 miles from source.

There are few surfaces, if any, to match a well-laid pavement constructed from reclaimed setts, so it's understandable why they are so popular for heritage projects and buildings of character, but all too often what should be a stunning work turns out to be a bit of a mess because the laying operatives don't have sufficient experience in laying setts and this is compounded by a designer or project manager who doesn't understand why sett paving is laid in a very particular way.