LATHING AND PLASTERING.
By the time that the outside finish has been brought to this stage, the inside of the house will have been given over to a new set of mechanics, the lathers. The trade of lathing, although a wood working trade, is in most localities distinct from the trade of the carpenter, and the lathers will have come to the building to put on laths and nothing else. For this reason it will be well for the super intendent to see personally that all of the furring has been completed and done properly. Walls, ceilings and soffits should be carefully examined to be sure that their surfaces are true, level and plumb; chimney breasts and projections of all kinds tried with a square to see that all angles are true, corners must be examined to see that nail ings are provided where the laths are to make an angle, and ;rounds and corner beads set wherever necessary for railings, or for a finish.
Corner Beads. The use of corner beads is a matter of custom, being general in New England, and more rarely used in the West. In recent years the use of metal corner beads has become common, and these are to be preferred where a sharp corner is desired. Either a wooden or metal corner bead should be used, as it results in a saving of time to the plasterer, and being set and rigidly secured by the carpenter while furring the house, a and square corner is assured. The superintendent should see that all beads are in one length, and that they are set plumb and square. Especial attention must be paid to arches, since the perfect shape of the arch is deter mined by the accuracy of the beads, and it will be difficult to remedy any defects after the plaster has been applied.
Lathing. 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 railings, 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 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.
Metal Laths. The use of metal lathing is continually in creasing and is a practice which should be encouraged even for wooden houses. This form of lathing holds the plaster more firmly and is not so liable to crack or sag, and it is almost impossible to detach it even if soaked by water. Added to this are the fire-resisting qualities, which render the use of metal lathing always advisable for the soffits of stairs in public buildings, under galleries and over all hot air pipes enclosed in partitions. Metal laths should always be used where wooden walls connect with brick walls or chimneys, and wherever a solid timber of any size is to be plastered over, a strip of metal lathing covering the timber and lapping well on to the adjoining wooden laths, will tend to prevent cracks which will occur if wooden laths only are used. For exterior plastering galvanized of painted lathing should be used, furred at least seven-eighths of an inch from the boarding.