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.
Fillets of stone may be built up with the wall to receive the slating, as described under the corresponding bricklayers' joint.
The fine joints of ashlar are usually formed with a putty composed of lime, white lead, and a little fine sand, the fine mortar of the joint being kept back about an inch from the face to make room for the strip, which not unfrequently, however, consists of plasterer's putty or even common glazier's putty. Thin plates or pieces of lead are sometimes used to obtain fine joints as well as a little desirable play in providing a bearing where there has been some uneasiness as to variable pressure in the case of a voussoir or column tambour. A change from very thick to thin joints took place in the eleventh century.
Fine Tooled Joint is made by finishing off the margin drafts, worked round the stone smooth and neat, with the chisel termed a tool, which has a cutting edge about 3½ in. broad, the remainder of the beds and joints being sufficiently dressed by knocking off the protuberances to allow the drafts to come close. Or the whole surface of the joint is tooled smooth after being boasted, the marks left by the boaster, which may be either smooth and regular or random and rough, being taken out by the tool.
Flushed Joint occurs when spalls, chips, or flakes are splintered off at the arris from a concentration of weight owing to the bed being worked hollow. It is also sometimes produced by the use of fat lime mortar, which only sets where exposed to the air, and consequently offers more resistance to pressure at the arrises than further back from the face. The same term obtains when the inside joints are filled up with mortar and brought up to a level flush with the top surface of the course without leaving vacuities, and before the mortar for the next course is spread. The process occurs in all descriptions of coursed masonry, squared rubble, or even random rubble if need be, for the latter admits of being every now and again brought up to level courses and flushed. In stone walling sometimes the ordinary mortar is mixed with one-third fine clean gravel for flushing purposes.
This will bo found described in the Bricklayers' Section.
Grooved Joint is formed when opposite grooves are sunk in adjacent blocks for the passage of rod bolts, or in the end joints of the stones in horizontal and raking cornices to receive white lead. Vertical grooves of some size are occasionally made in facing blocks for the reception of concrete backing. In constructing sea walls without cofferdams, the edges of granite slabs are sometimes grooved to embrace and enclose the projecting flanges of iron piles, the grooved joint being filled in from the top with cement. Concrete and rubble form a good backing to this arrangement, the rubble protecting the concrete until it is set, or sheet piling may be used instead. Iron piles can also be protected and surrounded, and a strong interlocking facing obtained by cutting grooves on the sides of blocks as well as sinking central holes through them by which they may be dropped over the piles. Slabs of stone are correspondingly cut to fit the grooves of the casing blocks, and being slid down into placo the grooved joints are gradually rammed tight with cement.