Section through the Roof. The dotted lines show the finish of the original scissors-bracing. The parts shaded show the additions made by Mr. Walter H. Godfrey when the hall was re-erected. Erected in 1470 for Sir John Crcsby, d. 1475.
Figs. 56 and 57 are the braced-rafter types, in each case, scissor-braced above the collar. In Fig. 56 each sixth rafter is arch-braced to corbelled wall-posts, the rafter being framed to the post with a sole-piece notched to the twin wall-plate, and the intermediate rafters are strutted with ashlar-pieces from the wall-plate. In Fig. 57 there are neither arch-braces nor wall-posts. This is an early type of high-pitched roof, and shows the development towards the next form, the barrel, which is really an arch-braced instead of a straight-braced rafter roof. Examples are shown in Fig. 58, Horwood; Fig. 59, Lapford; and Fig. 60, Tawstock Chapel. Fig 59 is ceiled in to barrel-form above the rood-screen. Fig. 61 is a rare double-coved and barrel roof, close-boarded in. The side-covings really mask hammer-beams, which carry the longitudinal hammer-plate. This arch-braced rafter, or barrel-form of roof is typical of Devonshire and Somerset Churches, although it is unsafe, at the present day, to attempt a classification of timber roofs into types of localities, without many drastic exceptions.
The roof of Crosby Hall, Figs. 62, 63 and 64, enters into the logical sequence of timber-roof development here, and also serves to show how narrow is the division line between a roof and a ceiling. Practically all of the visible woodwork of this roof is purely decorative, but the sectional view, - for the drawing of which we are indebted to Mr. Walter H. Godfrey, the architect under whose supervision Crosby Hall was removed from its former site in Bishopsgate to its present location in Sir Thomas More's old garden at Chelsea, - shows that it is really of the scissor-braced rafter variety. In the drawing, the dotted lines at AA show the original bracing, which was in a very decayed state at the time of the removal, and BB the new scissor-brace which was inserted by Mr. Godfrey, to strengthen the original bracing. At the same time the king-post C was also introduced. Fig. 64 is from an idealised sketch made by Herbert Cescinsky of the Hall before its demolition in 1908, and Fig. 62 shows it in its state as re-erected.
It is only this original scissor-bracing which removes this roof from the category of ceilings. Actually, a ceiling may be defined as the covering of a room or hall which is fixed to, and supported by either roof timbers or the joists of the floor above. Thus, the visible joists, even when carved and decorated, with the interstices filled in by the floor-boarding above, do not constitute a true ceiling, no part of which should be constructional, but merely decorative. Crosby Hall, therefore, can be described as having a ceiled decorative roof, of which the arched-ribs with their wall-posts are the only visible constructional members.
Fig. 65, the nave roof of Haughley Church, in Suffolk, introduces the tie-beam roof. This is distinguished from the cambered or firred-beam types in being higher in pitch, and in consequence, possessing a ridge-purlin, but without collars. In this example, the tie-beam is introduced between each alternate principal only, and is braced below to corbelled wall-posts, and above, from the beam to the purlin. The intermediate principals are arch-braced to wall-posts direct. At the junction of each brace with its purlin, and each principal with the ridge, is an applied pendentive ornament in the form of a carved floral boss.
Fig. 66 is a secular roof from a house in Lady Street, Lavenham, in process of restoration. The tie-beams are cambered, and the rafters are halved at their intersections without a ridge-purlin. To compensate for this a collar-purlin is fixed under the collars, and this is stiffened by a braced king-post from the centre of the cambered tie-beam. The end of the tie-beam, visible in the illustration, illustrates the decay often met with in these early timber roofs, to remedy which it is necessary to take the roof apart to repair it. In the illustration, it will be noticed that each joint has been marked to facilitate the re-erection.
Fig. 64. Crosby Hall, Bishopsgate. - From an idealised sketch by Herbert Cescinsky made in 1908.
Fig. 65. Haughley, Suffolk. - The Roof of the Nave. Span 24 ft. 6 ins. Length 58 ft. 4 ins. Late fifteenth century.
Of similar type is the nave roof of Edwardstone Church in Suffolk, Fig. 67, where the sag of the tie-beams, in spite of their camber, may be noticed. All four braces from the king-posts are tenoned into the collars, instead of the lateral braces being carried past them to the purlins, as in the previous example. In addition to this support, the collars are braced to the rafters, which, in turn, are ashlar-strutted from the wall-plates.
Fig. 68 is the nave roof of St. John's Church, Henley-in-Arden, of the arch-braced queen-post type. The tie-beams have an acute camber, and are arch-braced to corbelled wall-posts. The collars are high and small in scantling, and the roof is without ridge-purlins. So rare is it to find the queen-post type of roof before the Dissolution of Monasteries, that the presence of these posts may be taken as an almost infallible indication of the latter half of the sixteenth century, or even later. St. John's Church has a fine pulpit, which will be illustrated in a later chapter on the development of the English oak chest.
Fig. 66. Hall Of Timber House In Lady Street, Lavenham. - King-post type of roof with collar-purlin. Middle fifteenth century.
Fig. 67. Edwardstone, Suffolk. - Roof of Nave. Braced king-post and collar-purlin type. 17 ft. 10 ins. span.
Fig. 68. ST. John's, Henley-In-Arden, Warwickshire. - The Nave Roof. Braced queen-post type.