The timber roof, from the thirteenth to the sixteenth centuries, is such a triumph of the English carpenter, demonstrating equally his skill and inventive ability, that some little space must be devoted to its consideration.
Until almost the end of the fourteenth century, the joiner was content to follow the mason at a respectful distance. He imitated him in such things as canopies, tombs, sedilia and the like, and even the early chests, if they were coloured in close imitation of stone, would deceive an eye judging by form and general details only.
The mason hews out of the solid block the piece he is fashioning; the timber worker constructs. The carpenter builds a box with framed ends, front and top, cutting his framing from planks. He makes his framing, tenoning and mortising his styles and rails, fixing in his panels, either in grooves or rebates. The mason has no other alternative than to make his frame and panel in one, from the solid stone. In other words, stone offers greater resistance than wood to crushing weights, but it has not the tensile strength. A Gothic church made from wood or a tie-beam made from stone, would both collapse, the one from the crushing weight of the superstructure, the other from the sagging strain.
It is with the timber roof, as applied to churches and sacred buildings, that the early joiner first emancipates himself from the stone mason's traditions. There is very little hiatus in the evolution, where the timber roof is employed in secular houses, although such decorations as religious symbols, winged angels, and with rare exceptions, painting in colours, are absent. The secular timber roof, - that is, one which is left unceiled, and with its timbers exposed, and, therefore, ornamented in greater or lesser degree, - has a comparatively short life in England. With the decline of the Great Hall and the advent of the Long Gallery, the custom arose of ceiling in, at comparatively moderate heights, and ornamenting the ceiling with moulded plaster. This method had the advantage of permitting of the subdividing, under a large roof, into apartments of moderate size, the partition walls being taken up to ceiling height, whereas with the open timber roof, such subdivision is not possible, without forming a number of cubicles, the decorative effect of which in a house would be disastrous. Barn partitions offer good examples of this cubicle effect.
Concerned, as we are here, with origin rather than purpose, there is a very narrow line of demarcation between an ecclesiastical and a secular building, especially in the earlier periods. The builders of churches and cathedrals were not altogether clerical, nor the artisans engaged on work to private palaces wholly secular. Hampton Court and Eltham were built for a great Cardinal; Westminster Hall for William Rufus, and its present roof for Richard II. Anthony Bec's Hall at Durham Castle is entirely ecclesiastical, both in inception and workmanship, whereas Middle Temple Hall (although late, dating only from the reign of Elizabeth) is secular in about the same degree. In no case, however, does roof construction differ, in essential details, whether it be in palace or church. The development of the English timber roof, therefore, can be traced without any deviation, whether in buildings erected for Royalty, the Church or the laity. The evolution of the constructive principles is the same in all cases.
It may not be out of place here to assume that both the technical terms used in describing the parts of a timber roof, and the principles and problems which arise in its construction, are unknown to the general reader, and to attempt a simple explanation of both. It must be borne in mind that it is not possible, in such an explanation, to be both simple and complete, and the division line between the incomplete and the inaccurate is frequently very narrow.
For our present purpose, we can consider roofs under three heads only, flat, lean-to and central-ridged or pitched. The end of a pitched roof forms a gable, hence the term " gabled-roof," which is frequently, but erroneously, used.
A flat roof is formed by laying beams squarely across the walls, at intervals according to the strength required. Transversely across these beams, timbers of lesser size, - known as joists, - are fixed, any piecing in the joist-length being supported on the beam-thickness. Sometimes the joists are framed into the beams, producing a panelled roof of the Somersetshire type. Transversely again across the joists, close boarding is nailed, and on this boarding the final roof covering, of lead or zinc, is laid. Tiles or slates cannot be used on a flat roof, as we shall see later. If a finished appearance be desired, the under side of the close-boarding is decorated with applied tracery or carvings. Rich examples have the ribs moulded and carved, with bosses or foliations at the intersections.