If back plastering of the walls or roof are contemplated it is better, and fully as cheap in many localities, to use the Byrkit Patent Sheathing Lath for the outside sheathing, placing the keys on the inside, and the plastering can then be applied directly to the sheathing. This sheathing lath, a full-size section of which is shown in Fig. 181, has now been in use for about ten years and is highly endorsed by architects who have used it. It is made by special machinery from pine, hemlock, cypress and spruce sheathing in random lengths and in 4, 6 and 8-inch widths, the 4-inch being the best to use, as it affords less opportunity for shrinkage and buckling.

The strips are tongued and grooved so that when put together they form a solid surface. Machines for making this lath have been placed in over 250 mills, principally in the Northwestern States and along the Mississippi River, and it is carried in stock in all the larger cities of those sections of the country. As it is very light (weighing only about 1 pounds per square foot), it may be sent a longdistance at a small charge for freight.

143 Byrkit s Patent Sheathing Lath 200120

Fig. 181.

The cost at the mills varies from $8 to $12 per thousand feet, according to the locality, and when in the building the cost should not exceed 15 cents per square yard, including nails and labor. The principal use of this lath appears to be on the outside walls of frame buildings, the lath being applied to the inside of the studding in place of the ordinary wood laths and the sheathing on the outside of the studding being omitted, siding only being used on the outside. This construction, while greatly superior to common laths without sheathing, cannot be recommended except for summer cottages and a very cheap class of buildings, unless it be in comparatively mild climates.

This lath, however, is intended for use in place of ordinary laths wherever the latter are commonly used, as on walls, ceilings and partitions, and can be used to advantage in places where ordinary lath cannot be used without furring or in construction for which the latter is not suitable. Besides its use for back plastering it maybe used for an under floor, where an open beam ceiling is desired, for sheathing outside walls to be finished with "rough cast" and for making solid partitions of short lengths (as between closets), by nailing back to back, horizontally and diagonally, and clinching the nails. Such a partition would be very slow burning. When used on sliding door partitions there is no necessity for lining the pockets, as, being tight, nothing can get into the pocket. In fact there are many places about the average building where this lath might well be used, even if not used for lathing throughout.

Kg. .31.

From information furnished the author by architects who have used this lath, it appears to answer all of the purposes of the ordinary lath, besides making the partitions much stronger and increasing the stiffness or rigidity of a frame building, and under an attic roof or on outside walls it keeps out more cold than the ordinary lath and plaster. The plastering will not come off, and cracks no more than on ordinary wooden laths, and a less quantity is required for covering a given surface. To obtain the best results for inside work 4-inch lath should be used, interlocked at all angles as in Fig. 182, and the plastering should be three-coat work, the scratch coat being allowed to dry cut before the brown coat is applied.

For unsupported partitions of wide span the lath may be put on diagonally from the supports to the centre, thus materially relieving the centre of the beams under the partition and diminishing the tendency to sag.

This lathing should be included in the carpenter's specifications on account of the tools, etc., required in putting it on.