OUTSIDE WALL FINISH Sheathing. The first operation in connection with the applica tion of the finish is that of covering the framework with sheathing, which should be about 1 inch in thickness, and for the best work, dressed on one side. The sheathing should be placed diagonally across the studding when the frame is of the "balloon" variety, but in case of a braced frame the boards need not be so placed. With the braced frame, the boarding may be started at any time, but with the balloon frame it is necessary to wait until all of the studding has been placed in the outside walls. The sheathing should be laid close, but need not be matched, and the boards should be fairly wide, say S to 10 inches, or even more. The most common material for this work is yellow pine free from loose knots. Spruce or hemlock may be used with good results.
The roof sheathing is nailed on at right angles to the rafters but the boards are narrower. The width is usually 4 inches but 6 inches works well also. They are laid with spaces between them for the passage of air. These spaces are from 2 to 3 inches wide and are left for the ventilation of the shingling or other roof covering, and for the cheapening of the rough boarding.
Roof boarding is not laid diagonally, but if this were done a very much stronger building would be obtained than where the boarding is laid horizontally, because each board acts somewhat as a truss to bind the whole framework more securely together. Some curved work, such as round towers and bay windows, is boarded diagonally, when it is impossible to place the boards in any other way. Each piece should be well nailed to each stud or rafter with large nails, ten-penny or eight-penny, and no serious defects such as large knots should be allowed in the sheathing.
Building Paper. Building or sheathing paper is now placed over the sheathing to keep out the weather and to cover more com pletely the joints in the boarding. This paper must be tough and strong as well as waterproof, and must be easy to handle and put in place. It must not be easily broken as any hole in it is an opening through which the weather will surely find its way. There are a
number of different kinds of building paper on the market, prepared with various chemicals to render them as nearly waterproof as possible. Tar is sometimes used for this purpose. The paper should always be laid with a good lap.
Water Table. Starting at the bottom of a wood structure, at the point where the masonry foundation wall stops and the timber framework begins, the first part of the outside finish which meets the eye is the water table, so called because its purpose is to protect the foundation wall from the injury which would result if water were allowed to run down the side of the building directly onto the masonry. The water table, therefore, must be so constructed as to direct the water away from the top of the foundation wall. This may be accomplished in several ways, some of which will be described and illustrated.
Fig. 26S shows the simplest form which can be used for a building which is to be covered with clapboards (this covering will be discussed later). A is the foundation wall, which may be stone, brick, or concrete. B is the sill, which may he in one or two pieces and which has already been described at length. C is the boarding or sheathing, which in this case is flush with the outside of the foundation wall, the sill being set back about 1 inch from this face. The hoard D is nailed so as to cover the joint between the top of the foundation wall and the sheathing, and on the top of it is fastened the water table E, which is inclined downward and outward so as to shed the water. The piece F is inserted to set out the first and lowest piece of siding G.
Fig. 269 shows another way of constructing a water table for a building with clapboards. In this case the sill B is set back about 4 inches from the face of the wall A, and a block is nailed to the bottom of the boarding, as at C, so as to set the piece D out clear of the face of the wall. This piece is rabbeted at the top as shown, so as to take in the bottom of the last clapboard.