This section is from the book "A Treatise On Architecture And Building Construction Vol2: Masonry. Carpentry. Joinery", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
189. Common brick should be laid in a bed of mortar at least 3/16, and not more than 3/8 of an inch thick. Every joint and space in the walls, not occupied by other material, should be filled with mortar.
The best way to allow for the thickness of the mortar joint is by the height of eight courses of brick, measured in the wall. This height should not exceed by more than 2 inches, the height of eight courses of the same brick laid dry. As common brick are usually quite rough and uneven, it is not always easy to determine the thickness of a single joint, but the variations from the above rule, in any eight courses that may be selected, should be very slight.
Pressed brick, being usually quite true and smooth, may be laid with a 1/8-inch joint, though a 3/16-inch joint is probably stronger, as it permits the use of more mortar, thus filling the joints better.
190. The best method of building a brick wall is as follows: The two outside courses are laid first; the mortar is spread with a trowel, along the top of the last course of brick, to form a bed for the brick to lie on; next some of the mortar is scraped against the outer vertical edge of the last brick laid, and then the brick to be laid is pressed into its place with a sliding motion, which forces the mortar to completely fill the joint. Having continued the inside and outside courses of brick to an angle or opening, the space between the brick should be filled with a bed of soft mortar, and the bricks pressed into this mortar with a downward slanting motion, so as to press the mortar up into the joints; this method of laying is called shoving. If the mortar is not too stiff, and is thrown into the space between the inner and outer courses of brick with some force, it will completely fill the upper part of the joints in the brickwork, which are not filled by the shoving process. A brick wall laid up in this way will be very strong and difficult to break down.
Another method of laying in the brick between the inside and outside courses in a wall is to spread a bed of mortar, and on this lay the dry brick. If the bricks are laid with open joints and thoroughly slushed up with mortar, it makes good work; but unless the workmen are carefully watched, the joints do not get filled with mortar, and the wall will not be as strong as when the bricks are shoved.
191, Some bricklayers lay the inside courses dry on a bed of mortar, as described in the previous paragraph, and then fill all the joints full of very thin mortar. This is called grouting. No more mortar should be used than will fill all the joints. This method is not considered as good as those previously mentioned, because the mortar, being so thin, lacks cohesion, and does not bind the brick together as well as does stiffer and more tenacious mortar. Grouting should never be done in freezing weather; the mortar contains so much water that it freezes very readily and is then useless as a bond.