This section is from the book "A Practical Treatise On The Joints Made And Used By Builders", by Wyvill J. Christy. Also available from Amazon: Practical treatise on the joints made and used by builders.
Heading Joint is the same as that of the plumber.
Besides the description of the similarly termed joint given in Section X., which is more or less applicable to this trade also, it is proper to note that there are other distinct forms, two of which are represented in Figs. 153 and 154.
Mitre Joint occurs when rolls or mouldings are returned, and is made with the copper-bit, as described under that head in Section X.
This is described under its alternative names of Capped Joint and Zinc Roll Cap Joint.
S-Joint is used to unite two edges by means of an intermediate strip of S-shaped section soldered to both, as shown in Fig. 155.
This name is given to a joint formed by turning up the edges of two sheets or strips against each other, but one more than the other, and turning the greatest upstand down over the least, as in Fig. 156. It also occurs between a saddle piece at the ridge end of a roll and the ridge capping Formerly it was necessary to solder saddle pieces to the roll caps, but Messrs. Braby and Co.'s patent solid saddle piece dispenses with soldering.
The parts where the solder is to fasten on are brushed over with hydrochloric acid (otherwise muriatic acid, or spirit of salt), killed, i.e. turned into chloride of zinc with a few small pieces of zinc, and are then soldered with the copper-bit and fine solder, as described under Copper-bit Joint in Section X.
Wedged Joint occurs when strips or pieces of zinc are secured in position at their junction with masonry, etc, by means of wedges.
This is synonymous with fold joint, which has been already explained.
Zinc Roll Cap Joint is formed between two sheets of zinc, as already noticed under Capped Joint, of which it is, in fact, another name. A common way of making it is as follows : - A wood fillet, about ¾ in. wide and ½ in. thick, is nailed upon the boarding along the line of junction, and upon this fillet is nailed or screwed a wood roll, about ¾ in. high and 2 in. wide, with its upper surface rounded and lower part left square, and bevelled off to the width of the fillet. The zinc sheets are laid against this on opposite sides with upstands of 4 in. and 3 in. respectively, which are closely fitted to and bent over the roll, the longest overlapping the shortest; and then a zinc roll cap of cylindrical form is slid on, gripping both sheets where the roll is narrowest and making a snug joint, with ample play for expansion and contraction. This plan requires a piece to be soldered to the roll cap under the saddle at the central ridge, or under the flashing if only a lean-to covering, and also necessitates a short length of roll cap to be mitred and soldered vertically at the edges, or eaves; but Messrs. Braby and Co. cover flats, etc, with rolls provided with solid stop ends, so that their plan almost obviates throughout the use of solder.