Plates 1 and 2
Before starting the architectural drawing proper, one must be familiar with the two general methods of representing an object having three dimensions (length, width and height) on the sheet of paper which has only two dimensions (length and width).
One method is by Pictorial Drawings or pictures and the other is by Orthographic Projection Drawings.
To illustrate by a simple object, a brick is represented in the two above mentioned ways.
There are three kinds of pictorial drawings in common use which will be treated of at length under other headings. Only their distinguishing characteristics will be pointed out here.
Figure 1 on Plate 1 is a Perspective drawing of the brick in which it will be noticed that all except the vertical lines come together at what are known as vanishing points. The vertical lines on the brick are drawn vertically here. This is the way we actually see an object.
Figure 2 is an Isometric drawing of the brick, the characteristic of which is that all except the vertical lines of the brick are drawn toward the right or left at an angle of 30 degrees with the horizontal. The vertical lines are drawn vertically here as in the Perspective.
PLATE 1. PICTORIAL DRAWINGS.
Figure 3 is an Oblique drawing of the same object. In this all vertical lines remain vertical as in the others. The lines running lengthwise of the brick remain horizontal and those running from front to back are drawn upward or downward at any desired angle, usually 30 or 45 degrees with the horizontal.
These pictorial drawings each show three sides of the object, but in each of them either the edges are foreshortened or else some sides do not show in their true shape. This is what makes it impracticable to work from pictorial drawings.
So as to avoid these distortions the method of Orthographic Projection is used in making working drawings.
An Orthographic Projection drawing of the brick would consist of one drawing representing what would be seen by looking straight at the front of the brick, one drawing as if looking straight down on top of the brick, and a third drawing as if looking straight at the end of the brick. These three drawings would be arranged on the paper as in Fig. 4.
If a drawing of the bottom is required it should be placed directly below the front view, etc.
It will be seen now that the Orthographic Projection drawings show the true shape of the faces and the true length of the edges.
PLATE 2. METHODS OF REPRESENTATION.
The architectural draftsman must be familiar with this method of representation as all working drawings are made in this way. For those who are not fairly well acquainted with it, a study of the subject will be of value at this time.1
A building is represented in much the same way as the simple brick. A Perspective drawing of a simple building is given in Fig. 5, Plate 2. To show it in orthographic projection, a drawing would be made as though the observer were looking straight at the front as in Fig. 6; then as though looking straight at the side in Fig. 7 or 7a, and when looking straight down on top of it as in Fig. 8. The first three would be called "Elevations" and the last a "Roof Plan."
It should be noticed that the right side of the building, Fig. 7a, is drawn to the right of the front view. The left side, Fig. 7, is drawn to the left of the front view, etc.
If we imagine the building to be cut through parallel to the ground and the upper part removed as in Fig. 10, and then draw what is seen when looking straight down on the remaining part, we shall have what is called a "Floor Plan;" see Fig. 10a. It will be noticed that this horizontal section or Plan is taken at varying distances from the ground, when necessary, so that it may go through the features of the building which are to be shown on the Plan. This imaginary horizontal cut is taken along line A-A as shown by Figs. 6, 7 and 7a. Compare these with Figs. 10 and 10a.
If desired, a vertical section may be cut through from the front to the back of the house, one part removed, and the remaining part drawn as in Figs. 9 and 9a. This section may be taken at various places the same as the plan.
Plans, Elevations and Sections are the three devices which the architect employs to represent a building in orthographic projection.
The student should get this idea clearly in mind before proceeding with the work. A glance through the book just now will help him to see what Plans, Elevations, and Sections really look like. Notice for example the drawings of the Rae Cochran house on Plates 21 to 30.
1 Consult list of Reference Books, page 147.