The laths principally required by the builder are of two kinds - those used for plastering, and those used for roofs to support the covering of slates or tiles.

Plasterers' Laths are thin strips of wood, about an inch wide generally, 3 or 4 feet long, and of a thickness varying according to the work for which they are to be used (see Part II.)

They should be straight; free from large dead knots, which fall out and weaken them; from splits; and from sap, which leads to decay.

They are sometimes made by hand, sometimes by machinery. In either case they should be split or rent from the log, so that each lath has its longitudinal fibres intact. In sawn laths the fibres are generally cut across in places, which makes the laths weak and apt to break across.

Oak laths are sometimes used, but for ordinary work laths should be of the best Baltic fir.

Thickness

Plasterers' laths are made in three thicknesses classified as follows : -

Single laths . . . 1/8 to 3/16 inch thick.

Lath and half laths . . . 1/4 ,,

Double laths ... 2 ,,

They are made also in various lengths, varying from 2 to 5 feet, but the lengths most commonly used are 3 feet and 4 feet.

Market forms. - Laths are split in this country, and are also imported from the Baltic and from America, and sold in bundles, round or half round, being either the whole or half of a young tree split up.

The bundles generally contain 360 lineal feet, but sometimes as much as 500 feet run of laths.

Metal Laths are manufactured from 28 BWG iron in any lengths up to 36 inches. They are fixed in the same way as ordinary laths, and the key for the plaster is afforded by the dovetail form into which the metal is bent. They are of common fireproof, and are very useful in special circumstances.1

Slate or Tiling Laths, or Battens as they are often called, are generally sawn out of boards and sold in 10-feet lengths, the width and thickness varying from 11/4 inch x 3/4 inch to 2 inches x 1 inch, or even 3 inches x 1 inch.