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Early Roofing Systems in Northern Europe
Briefing Jumièges, Abbey Church of Notre-Dame | Warwick, Lord Leicester Hospital
  Medieval Carpentry: An Introduction
This briefing is designed as an introduction to medieval structural carpentry—a topic rarely included in conventional texts and courses on medieval architecture. Because this subject is likely unfamiliar, I will introduce some of the major types of carpentry, investigative tools and approaches, essential terminology, and some general building categories as a preparation and context for a more in-depth consideration of two monuments: the Norman Abbey church of Notre-Dame of Jumièges near Rouen, France, dating to ca. AD 1035–1067 and second, the timber-framed complex of urban guild buildings known as the Lord Leicester (Leycester) Hospital in Warwick, England, dating roughly between 1346 and 1571. These two sites have been chosen for their contrasts. They are nearly four centuries apart in date and differ considerably in their type of construction and their carpentry. Moreover, each demands a rather different approach and methodology, one essentially archaeological, and the other typological and contextual. Notre-Dame at Jumièges, for example, is a ruin without its roof or any other visible timberwork intact! It thus requires archaeological detective work and documentary sources to envision what is likely to have existed for the main span of the 11th-century nave. By contrast, the Lord Leicester Hospital dating mainly to the 15th century is almost invitingly familiar, certainly picturesque, and immensely rich in original timberwork. Here, the amalgamated buildings, acquired by and built for the united merchant guilds of Warwick, constitute an exceptionally well-preserved example of urban domestic architecture that can be typologically, socially, and stylistically related to the larger picture of medieval secular architecture of towns and countryside in the high and late medieval period.

France, Jumièges, Abbey Church of Notre-Dame, Aerial view

Great Britain, Warwick, Lord Leicester Hospital, Exterior view
As with all early buildings, and particularly those of wood that are so vulnerable to fire, we rarely find a structure of one building that has not been substantially altered, rebuilt, or restored. In fact, it might even be assumed, as the Beowulf poet expressed, that even the greatest of halls were by their nature doomed to perish in flames. Our evidence before about 1100 is extremely meagre, and the vestiges of carpentry or where an imprint of timber survives are fragmentary at best. Yet, as will be seen in the study example of Jumièges Abbey, traces of timber remain that provide important clues. Thus, scrutinizing a structure from an archaeological perspective is one of the ways in which we must approach the subject of building in wood.

Another important aspect of architectural history is context, which gives a building its meaning. What purpose or functions was a structure designed to fulfil? What did patrons and master builders wish to communicate in their architecture and how did they realize these goals? For obvious reasons, dating a structure and the phases of construction are fundamental to finding answers to these questions and to our understanding of the evolution of technology, style, and content. While a number of the buildings encountered in this course will have documents (Fabric rolls, cartularies, chronicles etc.) that offer evidence for dating the structural fabric, buildings of lower social status that made up the villages, towns, and agrarian environments of medieval Europe are often without documentation. Moreover, roofs hidden above vaults or ceilings are unlikely to receive the comments of admiring visitors, who might remark on such visible wonders as the shrines of saints or the fountains in a monastic cloister. Fortunately, a new tool has, so to speak, come to the rescue: dendrochronology. Dendrochronology (tree-ring dating) used for dating medieval timberwork has dramatically transformed archaeology and the study of material culture. Since its importance is so great, the discussion of dendrochronology has been developed as a separate section, but it should be kept in mind that it is fundamental to the information that follows here.

Medieval carpentry on a large scale includes buildings that are entirely of wood such as Saxon and Viking [link to secondary in section 3] earth fast structures (with posts sunk into the ground) known exclusively from archaeology as well as more advanced and permanent timber-framed buildings built on ground sills or low plinth walls of stone. Many of the latter have survived and can be seen in a variety of buildings types, such as the Templars' Barns at Cressing Temple, Essex, and other kinds of vernacular buildings ranging from ordinary cottages to much grander royal residences, castles, or manorial and municipal halls like the Lord Leicester Hospital. Timber-framed construction was widespread in ecclesiastical buildings as well, for example, in the so-called stave churches of Norway, dating mainly to after 1200, or the rarely-surviving parish churches with timber-framed walls and roofs, such as Marton church in Cheshire.

Substantial carpentry exists in roofs necessary to cover and protect masonry buildings whether they are vaulted in stone, brick, or timber, or have a wooden ceiling or open roof. The timberwork created by the carpenter needed to be strong and rigid in order to support the external roofing material, whether it was thatch, clay tiles, slate, or sheets of lead (the primary covering for the great cathedrals of Europe) such as Notre-Dame of Paris. In tall buildings like Gothic cathedrals, roofs needed to withstand considerable wind pressure and the stability of the structure often depended on the efficacy of the timber joints used to connect the members of the roof. The carpenter also needed to minimize horizontal forces (outward thrust) and to distribute efficiently the weight of the roof on the thin, upper clerestory walls. Medieval carpenters also needed to allow for water drainage by overhanging eaves or devise a roof whose seating would accommodate a guttering system on the masonry parapet. Hence in all great churches and many secular buildings, carpenters and masons had to work together as architectural partners in a carefully coordinated enterprise.

An important category of medieval buildings containing substantial timberwork is the aisled hall with load-bearing masonry walls. These structures include medieval barns, like the large Cistercian [secondary below] barns of Ter Doest, Belgium, or Great Coxwell, Oxfordshire, market halls of northern France, or monastic and collegiate refectories and infirmaries. The most important differentiation among the various functions and the design of these building types concerns fenestration; or, quite simply, the desire for light. Barns, for example, do not need windows for the central aisle, and thus, they generally have a single roofing system spanning both aisles and nave. On the other hand, churches, infirmaries, and domestic halls, like basilicas with clerestory windows [cf. Old St. Peters in Rome] often have separate roofs for the nave and side aisles; this was the case at Jumièges.

Regardless of fenestration issues, the timberwork in aisled buildings, as in the timber-framed barn at Cressing Temple (above) is relatively consistent and such structures typically employ supporting vertical posts (arcade posts), aisle posts in the outer walls, and a gabled roof over the nave consisting of cross beams (tie beams and collars), inclined members (common and principal rafters), and various braces and struts that use triangulation to stiffen the frame in the transverse plane, perpendicular to the longitudinal axis of the building. These frames are then connected lengthwise by longitudinal (axial) timbers set square to the ground and called plates, (e.g. arcade plates; aisle plates, sole plates, and wall plates); other longitudinal members set diagonally and connecting one main frame to the next and supporting common rafters are termed, purlins. Purlins may occur at the ridge of the roof (a ridge purlin), at the collar (a collar purlin), and in the slope of the roof plane (usually classified by the way they are attached to the principal rafter), a distinction that need not concern us here. Clear examples of purlins carrying common rafters can be seen in the views of Cressing Temple (above) and the barns at Leigh Court (below) and Westminster Hall.

Within the masonry walls, a bay system of construction is used in timber much as it is in stone. Thus, early aisled halls, like their masonry counterparts, have a main arcade (in wood) that supports a clerestory elevation; divided into bay units by vertical posts and tie beams, as has been suggested in reconstructions of the 12th century Norman halls at Leicester Castle and the Bishop's Palace at Hereford; the latter now consists of partially preserved arcades in the attic of a later rebuilding, but is nonetheless, an important survival of a probably widespread form of construction.

Evolution from the Aisled Hall to the Unaisled Hall

In the history of medieval carpentry, one of the key technological and aesthetic developments in large-scale buildings was the transformation from a divided, aisled hall to an undivided interior. Single interiors without internal posts were certainly common in humble, small-scale domestic buildings that employed inclined timber crucks (forks, furcae, in Latin), but the application of this type of construction on a larger scale was considerably more challenging. Cruck construction is essentially an A-frame design in which roof and wall are supported by the load-bearing cruck blades, as can be seen in the cross section and interior of the largest, timber-framed cruck barn at Leigh Court or, by contrast in scale, on the exterior of a modest tenant house in Stoneleigh Village, Warwickshire. Each cruck frame forms a primary bay division of the structure and is thus a principal frame in a series connected lengthwise by purlins. While the complex classification of cruck construction need not concern us here, it is important to note that impressive interior spaces using cruck blades (large curved timbers) have been recently dated by dendrochronology to the mid 13th century. Full cruck spans are naturally limited by the size of the trees available and rarely exceeded 10 meters; and yet impressive halls such as the four-bay hall at Stokesay Castle Shropshire, dated by dendrochronology to 1285 and spanning 31' internally, survives to illustrate how these massive timbers might be employed where the framing begins some distance up from ground level (and in fact, the original blades have been truncated). Generally, however, spans of half that distance or less would be more of a norm for ordinary houses.

Also appearing in the second half of the 13th century, a very versatile roof form, called a base cruck, emerged as an important means of spanning a hall without interior supports. This type can be defined as a roof consisting of primary transverse frames (the principals) that begin well below the wall head and rise to the level of the lowest transverse member, most commonly a collar. Base crucks, typically used in rather large scale, multi-tiered construction, had the advantage of adaptability to wide spans as well as decorative potentiality. Like full crucks, associated mainly with agricultural and lower status vernacular buildings, the base cruck hall is characterised by large impressive timbers and strong bay divisions, as for example, in the vast infirmary hall (16 meters, ca. 53' span) at Byloke (Bijloke) Abbey in Ghent (dendro, ca. 1251-55) and the 14th century ecclesiatical barn at Bradford-on- Avon, Wilts.

A fascinating exposition of the stages of transition from aisled to unaisled halls has been recently charted with considerable archaeological expertise at the Pilgrim's Hall, a hostel for wayfarers, situated in the Cathedral Close at Winchester in Hampshire and recently dated by dendrochronology to 1308. Originally, one base cruck formed the central roof frame of the south two-bay hall before it was cut away, and the hall was divided into two storeys in the 17th c. This principal frame consisted of thick inclined blades sprung from below the wall head with arch braces tenoned and pegged to their under sides respectively. Significantly, such curved bracing between a major vertical and horizontal member, enhanced the arched profile of the roof and also echoed the arch braces between the posts and tie beam on the aisled frames. By 1300, then, we can begin to chart the progress of the decorative open-timber roof and the multiple uses of moulded and curved members that became standard components of open roofs of later generations such as those in the Lord Leicester Hospital and the larger guild hall, St. Mary's Hall in Coventry, Warwicks.

In its present condition, only a fraction of the former Pilgrim's Hall survives and can be visited, but, significantly, as well as the base-cruck frame, it contains perhaps the earliest known example of a decorative hammer-beam roof with figural carving and, thus, may be regarded as the ancestor of Hugh Herland's magnificent angel roof at Westminster Hall, London, commissioned by King Richard II and erected piecemeal in 1395-96 to cover the unprecedented clear span of nearly 68 feet! While there are numerous other examples of splendid roofs either surviving or known from antiquarian sources, there can be no doubt that by the 14th century, the open timber roof, embellished by figural carving, heraldic devices, elaborate mouldings and tracery, had become a major architectural form exploited as much for its aesthetic as for its functional merits.

From this cursory survey of several major features of medieval carpentry and building types, we may conclude that for both structural and decorative reasons, roofs deserve major attention. Roofing systems, like vaults, piers, abutment, and fenestration display a wide variety of characteristics in design and structure; more importantly, they provide us with both technological and cultural insights. When looking at the roofs of medieval buildings in general and in particular those provided here in the case studies of Jumièges and Warwick, the following criteria are important to bear in mind: 1) overall building scale; 2) internal span; 3) the decorative and aesthetic features exploited; and, 4) the support conditions provided by the walls, where building in wood and building in stone interact.

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