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.
Radiating Joint is one whose direction is obtained from, or whose tendency is towards, a centre or axis. In a right arch it was formerly called a summering by workmen, and in bridges it not unfrequently commences at the foundation or timber floor of the piling, being concealed at times by the outer courses which are laid, for the sake of appearance, with level beds. This kind of joint ought always to be normal to the soffit, but in a skew arch it usually forms part of a spiral surface that twists round the axis of the cylinder, by which means an equivalent degree of strength is obtained. This surface can be easily imagined by supposing it to be described by a straight line travelling uniformly along the axis whilst revolving round it at the same measured rate. Radiating joints occur in quay walls built with a curvilinear batter, and also in circular work with level or inclined beds, in which case an iron rod may with advantage be driven into the ground where feasible as a working centre in case of its being necessary to refer to it to keep the courses to the proper curve. In spire ashlar with raking beds the joints are little benefitted by radiating towards the axis, owing to the magnitude of the angle of repose of dry masonry. Joints in tracery radiate to the centre of the arch, or circle, or arc in which they occur. Conical openings in walls, ribbed groins, domes, niches in circular walls, etc, have radiating joints. The back rebates of stone steps likewise acquire increased stability by being cut to radiate.
This is made in fixing a metal apron,etc, when there is no convenient mortar joint into which the turned-down edge thereof may be inserted. The mason cuts a raglet, or groove, or chasing for the plumber to insert therein and secure the edge, the raglet being about an inch in depth and sufficiently wide to take the edge of the metal and the lead wedges, or bats, or molten lead required to fix it.
Raised Joint is one brought forward from the face of the work, and is usually formed by raking, stopping, and pointing, so as to make the joint prominent with a flat, beaded, or angular finish. Unless very well done with good lime it is apt to split off in course of time, especially if the stopping was negligently suffered to be too dry when laying on the pointing stuff.
This is the same as described in the Bricklayers' Section, and is much practised in rubble masonry, so far as regards clearing out the joints prior to stopping them with a superior mortar to that with which the stones are set.
Rebated Joint is formed by sinking a rectangular one-sided groove along the edge of a block for doorcases, etc, similar to that described under Back Rebate, or to the rebate taken by the joiner out of a board. In the same way holes in sink stones and sinks for traps, and in stones for coal plates, etc, are rebated to make a suitable and efficient joint, either fixed or movable, as the case may require. The exterior facing of breakwaters built on the vertical system sometimes consists of granite, or beton, or other blocks, checked or rebated into each other.