Camelford Heritage Guidance

Camelford Heritage Guidance: Camelford c 1955 Number 1: Roofing Contents: 1.0 Introduction 2.0 Historic background 3.0 Roofing forms 3.1 Simple vernacular 3.2 Sleigh roofs 3.3 Double pile 3.4 Deep plan 3.5 Symmetrical roofs 4.0 Types of slating 4.1 Rag slate 4.2 Scantle slate 4.3 The Delabole System 4.4 Sized slates 5.0 Details 5.1 Fixing methods 5.2 Ridges 5.3 Hips 5.4 Valleys 5.5 Eaves 5.6 Verges 6.0 Roofscape features 6.1 Rainwater goods 6.2 Chimneys 6.3 Dormers 6.4 Rooflights 7.0 New work 7.1 Choice of materials 7.2 Attention to details 1.0 Introduction Camelford is an historic town with a variety of old buildings that give it a distinctive appearance. Whilst most of the buildings of Camelford are individually modest, their collective value is significantly higher than the sum of its parts. The special character of the historic streetscape is derived from the form of the buildings, the quality of the materials and the workmanship expressed in the form of constructional details. There has been a Conservation Area in the town since 1997 and a Character Statement was adopted as a Supplementary Planning Document. Whilst Conservation Area status does offer some limited extra controls to the Local Planning Authority, it does not of itself guarantee preservation or enhancement of the special qualities of the place. The cumulative effect of decisions made by local people regarding the repair and maintenance of their homes and businesses is the most significant factor in overall townscape quality. This is one of three Heritage Guidance Notes prepared with the aim of encouraging an approach to maintenance, repair and design that will preserve or enhance the character of the Conservation Area. The guidance herein is based on the premise that in historic settlements the sensitive repair and adaptation of heritage assets is fundamental to the broader aim of economic regeneration. This Guidance Note is intended to help owners, specifiers and contractors understand how individual features contribute to the sense of place; then to offer guidance as to how character can be retained or reinstated. The roofscape is a key element of the special character of Camelford 2.0 Historic Background The slate of North Cornwall, especially Delabole, has been exploited for centuries on a commercial basis and no doubt much longer for local use. It was used in prehistoric times for hearth slabs and has been used in buildings ever since. Exploitation for roofing slate is known from documentary sources which indicate export to Winchester in the early 14th century. It has been used throughout the world and retains its reputation for quality, longevity and attractiveness. No wonder it was ubiquitous on the roofs of Camelford in the past and remains the dominant material today. By the time of its establishment as a market town in 1259 it is clear that the production of roofing slate was an organised trading activity. As once the blue-grey slate of Delabole spread across the globe, so today the situation is reversed and cheaper slate is flooding in from South America, China and Spain. Each slate has its own character and qualities; Cornish slate is proven over hundreds of years of use to be durable and to patinate attractively. Imported slates may be cheaper, but their performance is unknown and their appearance is certainly different from the outset and will no doubt be equally evident as they age. Cornish blue-grey slate is the finest available 3.0 Roofing Forms The form, shape and pitch of a roof is indicative of the period of construction. The availability of suitable timber and the technical skills of the builders in roof construction dictated the spans that could be achieved, and consequently the plan form of the building itself. 3.1 Simple Vernacular The plain pitched roof is the most ancient form of construction. Starting with cruck frames and evolving to A-frames, they usually have a steep pitch of over 40 degrees. The ends of a detached building could be gabled, but were often hipped to save building time and resources. In Camelford the ancient building plots meant that buildings were commonly linked on one or both sides into informal terraces. The technical limitations and limited joinery skills available meant that such buildings were normally only one room deep. Not so many examples remain in the town as there was much adaptation and re-building between the 17th – 19th centuries. The simple vernacular roof lends itself to extension into T or L forms using the same basic tried and trusted methods. Simple vernacular roofs are characteristic and take a variety of forms 3.2 Sleigh roofs The desire to enclose more internal space in the most simple and inexpensive manner led to lean-to roofs being added onto the back of the building. These were often added as a continuation of the main roof in a form that is known locally as a sleigh roof. Whilst offering generous accommodation on the ground floor, sleigh roofs give little or no usable space to the first floor. A classic example of a ‘sleigh’ roof 3.3 Double pile Those who could afford it would build an additional block on the back of the original property. This was effectively two simple vernacular roofs back-to-back with a lead valley between. Such a form offered much more usable space – especially if the roofspace was brought into use as well. The drawback was, of course, the lead valley that would be prone to blockage and leaks. 3.4 Deep plan More complex roof structures were in use by the very wealthy from medieval times, but did not move down the social ladder until the later 18th and 19th centuries. Advancements in joinery techniques using king-posts, tie beams etc meant that much deeper plans could be covered without the need for costly and troublesome valleys. Many larger and later buildings in Camelford exhibit this form of roof. Some show signs that use of the roofspace was intended from the outset; presumably for servant accommodation. This image shows how plans became deeper as buildings evolved Greater quality control and more standardisation in the production of roofing slate, coupled with improvements in laying and fixing meant that shallower pitches could be formed. This allowed greater economy of materials in both construction and cladding. Old steeply pitched roofs had become unfashionable and were considered vulgar; but Camelford doesn’t seem to have been too interested in such things as fashion – that is in itself part of the charm of the place. 3.5 Symmetrical roofs Residents of Camelford may have been happy to continue to show off their local slate roofs, rather than hiding them behind parapets; but there are signs that the craving for symmetry and visually lightweight roofs did have some impact. A symmetrical roof form with a low pitch 4.0 Types of Slating The appearance of slate roofs changes over time; but each approach is, in its way, a response to the need for economy and efficient use of the resources available. Traditional use of randomly sized slates eliminated wastage by ensuring that most of the slate produced could be used. 4.1 Rag slate This locally distinctive type of roofing is characterised by the use of large, (sometimes very large), irregular slabs of slate. So large are the slates that they are fixed with nails directly to the rafters without battens, (though the term is often applied to any roof with large randomly sized slates, even if they are fixed to battens). The largest slates are used at the eaves and verges and become generally smaller moving up the roof slope. As a unique approach to roofing, rag slate roofs are a finite and precious resource. Relatively few rag slate roofs survive in Camelford and they need to be cherished. The random character of a ‘rag’ slate roof 4.2 Scantle slate The term is applied to a variety of roofing techniques that all involve the use of slates in varying size. Larger slates are used at the eaves and on the verges to offer more resistance to wind; the rest of the roof is filled with smaller slates with a general reduction in size towards the ridge. A further characteristic of scantle slating is that the slates are hung onto riven laths using wooden pegs and bedded onto lime mortar laid on the head of the course below. Subtle variations of slate size epitomises the scantle roof Due to the tendency for slippage and loss of slates to occur, when pegs either rot or fall out, surviving roofs are often covered in cementitious slurry or have been ‘turnerised’, (covered with a bitumen soaked hessian cloth). Turnerising hides the slates and makes their re-use difficult 4.3 ‘The Delabole System’ A common feature of both rag and scantle roofs is that the slate is laid in random widths and diminishing courses – though in both cases this can be a bit haphazard depending on the slate available and the preferred methods of the slater. During the 19th century this tradition was refined and eventually set out as a defined system. The Delabole System allowed the skilled slater to plan the guage for battens once the slates had been sorted and stacked in various lengths. The church roof shows the Delabole system using smaller slate sizes This system remains the pinnacle of the slater’s craft and the resulting roof is of such character and quality that it is without compare.

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