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.
Expansion Joint is one devised for averting the disastrous effects of interrupted expansion and contraction due to changes of temperature. The mediaeval plumbers as a rule laid lead as loose as possible, and were as lavish of lap joints as sparing in the use of solder. In metallic roof coverings rolls and drips and flashings are the usual artifices. In order to render their joints air or water tight, and at the same time to allow longitudinal motion, cast iron socket pipes have their cavities between the spigot and faucet closely packed with gaskets and grease, or hemp and red lead, or rings of india-rubber in the case of hot-water pipes, as described under India-rubber Joint. An expansion of 1 in. is usually allowed for every 80 feet of cast iron piping. Long lengths of ventilating pipes require expansion joints which, when of lead, are frequently made as described under Slip Socket Joint. An elastic joint is merely another term for an expansion joint invested with slight powers of extension through the medium of an elastic substance, which cleaves sufficiently tenaciously to the parts connected during their slight motion to preserve the tightness of the junction. Amongst the patent varieties Messenger's is a neat and economical example. This is intended for hot and cold water and gas, and consists of an india-rubber or other packing retained in the cavity of the socket by means of a loose iron ring encompassing the spigot end, and which is drawn up and bolted to the socket with nuts and screw bolts.
This maybe either a socket, slip socket, or astragal joint.
Flange Joint is a wiped soldered joint between two pipes, and is made with one flange only, which may be tafted back by degrees and by taking great care after the pipe has been opened out, but some plumbers cut the flange out of a piece of milled lead with the necessary orifice and to the desired diameter. This detached flange is then placed over the hole in the floor or cistern, etc, where the joint is to be situated, and the pipe is passed up through it without the edge being rounded off as with block joints. Its end is opened out with the tanpin as described under Taft Joint, and the flange and pipes being all properly shaved and prepared for wiping, the whole are united in the usual way quickly and with plenty of solder. Another kind of flange joint occurs when a lead flange is soldered to a lead pipe to correspond with the flange of an iron branch to which it is to be joined.
Red lead and hemp packing are inserted between the flanges, and an iron ring or washer is placed behind the lead one previous to bolting all through together with screw bolts and nuts.
A kind of lap joint formed by covering with a flashing the upstanding edge of a sheet of lead in a gutter, etc, or protecting by the same means any part of a roof cut into by the protrusion of gables, dormers, chimneys, skylights, etc. A flashing consists of a strip of 5 lb. lead, from 5 in. to 16 in. in width, secured along one edge to the wall with wall hooks, or else by tucking it into a groove or joint, whilst the other edge is left free and dressed so as to fall about 3 in. over the upstanding edge, which is about the same width as the flashing, or over or under slates, etc, as the case may be, so as to make all weather-tight and avoid checking any lateral motion of the lead during changes of temperature. In those cases where the flashing is notched and let into a succession of joints one above the other to accommodate it to an inclined upstand, it is termed a stepped flashing. The flashing at the feet of chimneys tucked into a joint, and lying down on the roof so as to allow the side or raking flashings to lap over it, is termed an apron or apron flashing, which title is applicable to any flashing that hangs over and covers an upstanding edge ; but where an apron occurs, the flashing under it is not fixed.