When it is found necessary to make alterations or additions to an existing building, the draftsman finds himself in need of a graphic record of the structure as it stands. If the original drawings of the building are not available, it is necessary that measurements be made and recorded in some quick and accurate manner so that workable plans, elevations, etc., may be drawn from them. The amount of detail and care with which this record must be made will be determined entirely by the new work to be done and will vary with every case.
The first record is made on coordinate paper. This paper is ruled vertically and horizontally with lines 1/8 inch apart forming 1/8 inch squares. Every eighth line is heavier than the other seven, thus forming 1 inch squares also. As the sketches are usually made at a scale of 1/8" = 1' - 0", the plans, elevations, etc., may be easily drawn on this paper in good proportion, for each small space represents one foot at this scale. The paper should be fastened to a piece of cardboard or other lightweight board so that it may be easily carried and marked on. A 6 foot folding rule and a steel tape will be needed for making the measurements.
Care should be exercised to make the notes complete at first, for if anything is omitted, much time may be wasted in repeated trips to the building for the missing information.
First, the floor plans should be measured and recorded. These should show all principle dimensions of rooms, the location of stairways with the number and dimensions of the risers and treads; then the thickness and material of all walls, the width, character and location of all wall openings and then any other features such as heating and plumbing equipment, etc., are recorded. In connection with the plans, any horizontal sections, such as window jambs, etc., may be detailed as needed. As a check to the numerous smaller dimensions of the plan, over-all measurements should be taken. They may be secured outside the building or on a straight line through the inside where doors are conveniently located.
In recording the vertical dimensions, the story heights should be secured first. This may be done by dropping the tape down through a stair well where the building is such as to make this possible. They may be measured also on the outside wall from sill to sill of the windows and then adding the sill-to-floor dimensions of the lower story and subtracting corresponding dimension of the upper story. The height and detail of belt courses, cornice, etc., must then be secured. At least one of each type of window and door openings should be shown in detail on these sketches. Where it is impossible to measure outside heights directly, the number of brick courses or of siding boards may be counted and, by measuring these features where they are within reach, the inaccessible dimensions may be arrived at. Another method of obtaining such dimensions is by taking photographs of the elevations, preparing a scale from known dimensions on the picture and using this to measure those parts that are out of reach. Roof slopes, chimney heights, etc., may also be found if the pictures have been taken from the proper station points. The photographic record will be found of much value in the subsequent work.