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.
Capped Joint is made between two sheets and in the direction of the current by means of a roll cap when zinc is used for roofs over boarding. One of the best descriptions of cap, and that adopted by Messrs. F. Braby and Co., the celebrated manufacturers of zinc roofing, consists of one formed out of a strip of sheet zinc and bent down over a wood roll, being confined with clips and fork connections (as further explained in the succeeding paragraph) so as to cover the upstanding edges of the sheets on both sides of the roll, and afford play for expansion and contraction whilst preserving its own position. Drawn roll caps consist of wood rolls with the zinc drawn over them by machinery. These only require to be laid upon the upstanding edges and fixed with screws down upon the boarding, the edges of the sheets fitting into grooves run on the underside of the rolls. In some cases three-quarter round strips stiffened with turned-up edges are slid on without wood rolls, and securely clasp the upstands through their elasticity, but these and other kinds require soldered ends, whereas Braby's zinc and square roll caps with saddle caps and stop ends, which are solid and not soldered, as described in their unique pamphlet on zinc roofing, appear to answer exceedingly well. The joints likewise between the turned-up ends of the sheets and the ridge zinc covering are capped. Other remarks relating to this joint will be found under Zinc Roll Cap Joint.
Clip Joint is one secured with zinc clips, and both the sides and ends of zinc sheets are thus jointed when the plain roll cap is used. The clips are strips about 2 in. wide laid under the wood rolls about 3 feet apart, with their ends turned down to clip the upstands of the sheets. The loose zinc roll cap is then slipped over and along, with fork connections inside soldered on to slip into the hooks of the clips. Such is a plan adopted by Messrs Braby and Co. Clips of similar width are likewise used with the fold joint. Drip Joint. - This is made in a similar manner to the lead drip, but soldering has to be resorted to at the angles. Flashed Joint. - This is likewise the same in principle as the corresponding lead joint, excepting that solder is occasionally necessary, and that the edge of the flashing is all the better for being stiffened with a bead.
This is shown in Fig. 151, as made by
Messrs. Braby and Co. It is used for uniting the upper and lower edges of sheets of zinc laid on boarding, having a slope at least of 1 in 7. Clips of the same metal about 2 in. wide are nailed to the boarding and doubled in between the edges of the sheets, whereby they are secured without too much restraint.
Folded Joint is a fixed joint, and not adapted for outside work like the foregoing. It is made by means of a fold, which is hammered and soldered.
This is shown in Tig. 152. There are, however, other varieties.