This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Being satisfied that the rough work has been put in place correctly, the lathers are set to work, and it will be well to visit the building before much of the lathing has been done, to see that the laths are given the requisite number of nailings, and are spaced properly. Three-eighths of an inch apart is the right width, but there is generally a tendency to put them too near together, in which case the mortar will not press through and form a sufficient key. If spaced too far apart the wet mortar will not sustain its own weight. The matter of breaking joints is another important matter, the usual way being to break joints every sixth course (A, Fig. 41), but a better ceiling is obtained by breaking joints at every lath. Over door and window openings the laths must extend at least to the next stud beyond, to prevent cracking (B). The direction of the laths must never be changed, and this is a point which will need to be remembered, as there is a great temptation to fill small spaces which occur with laths running diagonally or otherwise, even if they come at right angles to the other lathing (C). This must not be allowed; as cracks are sure to appear where the change in direction occurs. The laths themselves should be well seasoned and free from large or black knots, bark or stains. Bark, which is usually found on the edges, is a serious defect, and any laths showing this should be pulled off and fresh laths replaced, as it will invariably cause a stain in the plaster.
Fig. 41. Lathing.