An early common tiebeam roof: St Georges-de-Boscherville, seine-maritime, France: St Georges-de-Boscherville, seine-maritime, France

THE TRANSEPT roofs of the abbey church of St Georges-de-Boscherville date substantially from the construction of the original building, finished c. 1130. Minor differences apart, they consisted of common rafters and ashlar-struts, supported by longitudinal ‘box frames’ standing on massive close-set tiebeams, the latter being grooved at their lower edges for a boarded ceiling. Roof structures of this period are extremely rare, but Boscherville is unusual in the lack of integration between rafters and ties, the emphasis on longitudinal rather than lateral stability, and the box frames which achieved this, otherwise known only at Manglieu (Puy de Dome), It is therefore important in representing a stage in the development of large-scale roof structures in northern Europe before the introduction of the long-lived trussed rafter system in the early 13th century.