This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
There are two occasions for making measurements of old buildings; one, when it is proposed to make alterations; the other, for the sake of study, making drawings of portions either for immediate study or future reference.
Materials. It is a good plan if possible to take a small drawing board, T-square, and triangles to the building. Cross-section paper ruled one-eighth inch between light lines and one inch between heavy lines is very convenient. See illustration, Fig. 22, showing use of cross-section paper. Drawings may be laid out directly to scale on this paper, at one-eighth, one-quarter, or one-sixteenth inch to the foot, or details drawn at three-quarters inch to the foot, or full size.
Measuring Tapes. The dimensions should be taken with a tape, and for architectural work a "metallic" tape or cloth reinforced with fine wires and having clear figures, is very satisfactory, though it will be advisable to use a steel tape for very accurate work.
Datum Lines. As a general rule, it is best in frame buildings to take the horizontal measurements on the sill line, making a small section to show the relation of the sill to the walls. In brick and stone buildings they should be taken on the outside wall face or ashlar line. For heights, the finished floor levels should be taken as starting points, the main first floor of the building being the general datum. If there are many projections in plan it will be well to draw a straight base line and measure it from this line. If old buildings are out of level it will be necessary to use a straight edge or draw a level line on the wall and measure up and down from this level.
Hand Level. The hand level will be found very convenient for obtaining approximately the grades about the building. This is a small instrument used by railroad engineers in working out the elevations on each side of the track. The level can be also obtained by looking toward the horizon, pulling down the hat brim until the point coincides with it, turning on the heel carry the horizon level to the direction desired. This will give a point at the level with the eye.
Elevation Measurements. Total distances should be taken, and interior heights from floor to floor (with thickness of floors) should be run from basement floor to top of roof, and if possible a line should be dropped down the outside of the building to check this. It is well to mark size of glass, and give outside dimensions of sashes, taking dimensions to centers of windows or edges of stone or brick openings. Measurements are given by some architects from frame to glass openings. Sketches or details should be made of typical windows, and variations from the type. Roof pitches may be obtained by a level and measuring the rise per foot, or outside dimensions and total rise may be taken. A convenient instrument for doing this work is a twelve-inch single-jointed rule and level, shown in Fig. 23. Arches. In measuring arches, the height A, Fig. 24, from the ground to the spring of the arch should be given, the total height B, and the width C. The curve is obtained by giving the length of the radii or by laying a straight edge, D F, against the curve and measuring the distance D E, which will locate one point in the curve. Other points may be taken by offsets from the straight edge.
Fig. 23. Twelve-inch Single Jointed Rule and Level.
Inaccessible Portions. In places where it is impossible to reach the point it is desired to measure there are several ways of obtaining the dimensions with considerable accuracy. A photograph should always be taken of the building measured, and a proportional scale can be made from the known dimensions, which can be used on the photograph for determining unknown dimensions.
Approximations. In brick, stone, clapboarded or shingled buildings the different courses may be counted and the totals figured from those that can be measured. Where rapid memorandum sketches are made distances may be easily obtained by pacing, some men taking nearly a three-foot pace, others walking easily five feet in two steps. In this case every other step is counted as five feet. The total heights may be obtained by measuring up as high as can be reached, then standing at a distance, holding a pencil at this known height, measuring the distance by the eye to the top of the building. Or, a man's height can be taken to gauge the approximate height. The foot rule may be held up at such a distance from the eye that every quarter inch corresponds to a foot on the building, and the dimensions can be read off in this way.
Rubbings. Rubbings may be taken of tablets, lettering and flat ornaments by laying paper on the ornament and rubbing over it with a shoemakers' heel ball. The pattern cut in will be left white and the rest of the surface will be blackened by the heel ball.
Fig. 24. Measurement of Arches.