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.
This is explained under Bonding Joint, and may be made by lapping or crossing. It is essential in all good bond, and is introduced wherever possible at all the parts of the composite carcase, whether of stone, brick, wood, or iron.
Cement Joint is generally made with Portland cement and sand quite free from impurities where strength is required. For any other reason but that of economy the less sand mixed with it the better. Work hurried forward should be executed with quick setting cement, otherwise there will be unequal settlement. Neat Roman cement sets in about fifteen minutes, but gauged with an equal quantity of sand requires much more time. For a rod of reduced brickwork, about 75 bushels of cement and sand are required - and about 150 gallons of water and 37½ bushels of cement, supposing the Portland cement and sand to be in equal proportions. Cement bond is nothing more than three or four courses of brickwork in cement, which should be kept back from the face so as not to interfere with the pointing. When lines of hoop iron are built in it becomes hoop iron bond.
Chimney Pot Joint is formed by setting the pot or can, when of the red earthen or other similar kind devoid of collar, on the top of the orifice of the flue in cement mortar and well flanching it therewith, and sometimes additionally protecting the joint from the ingress of water by means of a flanching or covering of tiles bedded in cement. Terra cotta and other moulded or ornamental pots are often provided with a projecting collar near the base, so that in their case the base is stepped into the orifice and the joint made tight by flanching in the usual way.
This does not exceed in thickness ¼ in., and always requires good workmanship. Brick arches should be close jointed at the intrados. In this trade close joint is perhaps more correctly termed thin, whilst fine or very fine more particularly applies to those common to gauged work, which ought not to be more, and are sometimes less, than 1/8 in. thick.
This may be defined to be one thicker than is agreeable to the eye. The outside limit of thickness in good brickwork may be set down at ¼ in., whereas 5/16 in. may be assumed to be a fair working average for ordinary facing. A thickness of ½ inch and upwards may therefore be reckoned coarse, though frequently met with, especially where deformed and irregularly shaped bricks have to be worked in. It is necessary to remember, however, that where strength and not appearance is the desideratum, if the mortar is stronger than the bricks there can hardly be too much of it, whereas if it be weaker there can scarcely be too little. On the other hand, where appearance only has to be considered thick joints are inadmissible ; and so they are, having regard to the quality of mortar customarily mixed up and used by speculative builders, for it is not stiff enough nor adapted to withstand the squeezing produced by the weight of several courses while yet in the green state. Thick joints induce unequal settlement, are more pervious to rain, and require repoint-ing oftener than thin ones. Sometimes when the old standard of four courses to a foot or thereabouts has been insisted on, the bricks not coming up to the expected thickness have caused the bricklayers to make coarser joints than the designer of the fabric desired. When there is any doubt as to the thickness of the bricks, it is better to stipulate that no four courses shall rise more than a definite extent besides the height of the bricks, and to avoid thick joints the bricks must be equal sized and well shaped.