Laying Out

LAYING OUT Having now considered the material and the most important of the tools with which the carpenter performs his work, we shall pass to a consideration of the work itself, and see how a building of wood construction is put together.

Ground Location. In undertaking the construction of any building, the first thing to do is to make a thoughtful examination of the piece of ground upon which the structure is to be placed. This is very important as the character of the soil upon which a dwelling is located will very largely determine its sanitary condition, and will influence to a great extent the health of the occupants. Very often a- difference of a few yards in the location of a building will be enough to cause the difference between a perfectly dry cellar and one which is constantly flooded with water. Water is, indeed, the one thing above all others which must be guarded against, since it is impossible to keep it out of a cellar which is sunk in damp ground, unless some elaborate system of waterproofing is employed.

Ground Water. Below the surface of the earth there is always to be found what is known as "ground water." This stands prac tically always at a level, and is not met with so near the surface on a slight knoll or other elevation as in a depression. If possible, a house should be located on comparatively high land, so that the floor of the cellar does not come below the ground-water level. Below the surface of a hill, however, there may be a stratum of rock which will hold the rain water and prevent it from sinking at once to the ground-water level. Such a ledge of rock causes the water to collect and then flow off in small subterranean streams, which will penetrate the walls of a cellar if they happen to be in their path.

A good way to discover the depth of the ground-water level or the existence of rock ledges beneath the surface of the ground, is to dig a number of small, deep holes at various points of the site. These should be carried below the proposed level of the cellar bottom. A suitable location for the building may thus be chosen. If, however, it is not easy to make so thorough an examination of the site as this would allow, another method may be employed. This consists in the use of an instrument called an "auger," which is very much.like an ordinary carpenter's auger or bit, though much

larger. The auger generally used is about 2 inches in diameter. It is driven into the ground, and as it descends into the hole which it bores it brings to the surface small portions of all the different kinds of material through which it passes. This material may be preserved and examined at leisure. The character of the site may be determined in this way.

Staking Out.

When the approximate position of the structure has been decided upon, the next step is to "stake it out," that is, the position of the corners of the building must be located and marked in some way, so that when the excavation is begun the workmen may know what are the exact boundaries of the cellar. This "staking out" should always be carefully attended to, no matter how small the building may be. In works of importance it is best to have the work done by an engineer, but on small work it is customary for the contractor or the archi tect to attend to it. It is well to have at hand some instrument with which angles can be accurately measured, such as a transit; but the work can be done very satisfactorily with a tape measure and a "mason's square." This simple instrument is composed of three sticks of timber nailed together as shown in Fig. 32, to form a right-angled triangle. It is important that the tape used should be accurate, a steel tape being always preferable, and that the mason's square should give an exact right angle. A mistake in the staking out may cause endless trouble when the erection of the building itself is begun, and it is then too late to remedy it.

There are several different lines which must be located at some time during the construction, and they may as well be settled at the start. These are: The line of excavation, which is outside of all; the face of the basement wall, inside of the excavation line; and in the case of masonry building, the ashlar line, which indicates the outside of the brick or stone walls. In the case of a wood structure only the two outside lines need be located, and often only the line of the excavation is determined at the outset.