The next development was to suit further members to help with the soundness of the roof in windy conditions and these were known as ‘sous-laces’ or braces. On roofs made on substantial masonry walls that were conjointly terribly thick, any struts or ‘ashlars’ were introduced to stiffen the lower section of the couple. Fig: 1.2 illustrates this kind of construction, the plate being well-fastened to the wall with an all-time low member of the stone halved over it to stop the roof slippery on the highest of the wall.





These currently terribly substantial ‘couples’ began to be spaced more apart and have become called‘principals’. Between these main members, easy couples or ‘rafters’ were placed, however, to avoid sag or to accommodate longer rafter length presumably not on the market in one length of timber, associate intermediate support was required and this was known as a ‘purlin’. The purlin is successively supported by the principal couples, as shown in Fig: one.3.



