Related Building: Boscherville | Jumieges, Abbey Church of Notre-Dame | Briefing | Professor Lynn Courtenay

Early Roofing Systems in Northern Europe

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France, Jumièges, Abbey Church of Notre-Dame | Related Building: Boscherville
Professor Lynn Courtenay

The abbey of St. Georges stands in the commune of St Martin-de-Boscherville, 10 kilometres west of Rouen in the Seine valley not far from Jumièges. Originally founded in ca. 1060 as a house for secular canons by Raoul de Tancarville (d. 1079/82), chamberlain to William the Conqueror, it was refounded in 1114 as a Benedictine abbey, the canons being replaced by an abbot and ten monks from the illustrious frontier abbey of Saint-Évroult (Orne). Boscherville thus shares the elite patronage associated with Jumièges and the Norman dukes.

For our purposes, the transepts are of critical importance in that they contain some of the earliest roof carpentry in northern Europe.


France, Boscherville, St. Georges, Transept, Detail		France, Boscherville, St. Georges, Transept, Detail		France, Boscherville, St. Georges, Transept, Detail

While the complex sequence of the carpentry of the two transepts need not concern us here, the survival of the Romanesque roofing system above the vaults in both transepts is pertinent to the discussion of Jumièges. The most important features are: 1) the system of closely-space tiebeams (called common tiebeams), most of which have been cut when the masonry vaults were inserted ca 1225, and, 2) the presence of axial timbers (roof plates) that support a box frame for the roof structure, and 3) the presence of cut grooves in the sides of the tiebeams. One should observe that the lower axial plates are trenched where they cross the tiebeams, and some of these cuts correspond to the truncated tie beams, indicating clearly that the plates predate the truncation. They also demonstrate joining timbers end to end by means of diagonally cut scarf joints with three pegs.

The tiebeams extend to the outer face of the wall and are 12.5 m long (the internal span of the transepts being 8.7 m); these beams measure 22 cm x 40 cm in cross-section and are spaced about 90 cm centre-to-centre, not unlike the tiebeam spacing in the slots at Jumièges. It is clear that originally, all were complete, but now six of the ten tiebeams in the south transept have been truncated (as have seven of the twelve tiebeams in the north transept). The ties were presumably cut to facilitate vault construction in the 13th century.

Of particular relevance for the existence of ceilings in ecclesiastical architecture and the primary sources cited earlier, are the precisely cut, rectangular grooves (see tiebeam detail) that run along the full length of both sides of each tiebeam. These grooves are 4 cm across and 2.5 cm deep and occur 6 cm above the base of the tiebeams. Based on comparative evidence at St. Michael's at Hildesheim and St. Vincent at Soignies, it is likely that these grooves provided housing for the construction of a timber ceiling.

At Jumièges, corresponding evidence for a ceiling is far less evident than at Boscherville. It can only be stated from an examination of the masonry that the eight coggings (above) would permit the insertion of timbers with a cross-sectional dimension of roughly 14 x 19 cm. If the coggings were intended for axial timbers, they may have been part of the structure for a flat ceiling, rather than used as supports for vertical posts as in the transepts at Boscherville—an hypothesis based on the number and closeness of the coggings at Jumièges. Whether or not the 11th century tiebeams at Jumièges were grooved like those of Boscherville is impossible to know, but the proximity and patronage links between these two abbeys makes a tempting hypothesis that the chamberlain of Normandy would have emulated the interior design of his more prestigious neighbour.

While we can never know the precise design of the first roof at Jumièges and how it might have been braced, we can discern the scale and sectional dimensions (scantling) of the carpentry. The dimensions of the tie beams have already been indicated (ca. 26 x 31 cm) and archaeological evidence exists for the approximate rafter size of the romanesque roof at both ends of the nave. From the mid-level roof scar on the west face of the crossing tower, a rafter height of ca. 18 cm was measured, thus suggesting a maximum rafter size.

At the west end of the nave, the inner faces of both towers contain a series of narrow, oblique slots placed three courses of masonry above the tie-beam sockets discussed earlier. These angled housings are ca. 30 cm deep but only ca. 12 cm in width and are cut at an angle of ca. 40 degrees, corresponding to the pitch of the original roof of about 39 degrees. This evidence thus suggests a rectangular-sectioned rafter of a maximum of ca. 12 cm x 18 cm. or somewhat smaller.


France, Jumièges, Abbey Church of Notre-Dame, North tower detail		France, Jumièges, Abbey Church of Notre-Dame, South tower

In sum, the 11th-century, main-span roof of the nave of Notre-Dame comprised a series of closely spaced, tie-beam and rafter trusses of light and uniform section without longitudinal bracing above the base of the frames. These were presumably set within the bays defined by diaphragm arches, and hence the need for longitudinal bracing was not critical. Structurally, this roofing system placed a uniform load on top of the tall thin clerestory walls reinforced only by comparatively shallow wall buttresses.

It cannot be known whether horizontal collars were used to tie the rafters at a higher level. Early roofs that have been recorded like St. Denis in Liège and St. Gertrude in Nivelles suggest that vertical, canted struts without transverse collars may have been a more likely choice. To date, it can only be suggested that axial timbers supported a planked ceiling in the eastern bay of the nave, which, significantly, was part of the liturgical choir.

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