Working Drawing Concepts Chapter 2 Working Drawing Concepts Sketching • Orthographic Projections • Dimensioning • Architect’s Scale • Linear Measurement • Symbols and Conventions

Sketches convey ideas graphically and are drawn using basic tools such as pencils, paper, and erasers. Sketching is the process of drawing without instruments. Sketches are made by the freehand method. The only tools required are pencil, paper, and eraser. See Figure 2‑1.

Plane figures are geometric shapes with flat surfaces. A plane figure is a geometric shape with a flat surface. Common plane figures include circles, triangles, quadrilaterals, and polygons. See Figure 2‑2.

Pictorial drawings show height (H), length (L), and depth (D) in one drawing. A pictorial drawing is a three-dimensional representation of an object. Pictorial drawings show the three principal measurements of height, length, and depth on one drawing. Three basic types of pictorial drawings used in the building trades are perspective, isometric, and oblique drawings. See Figure 2‑3. Common uses of pictorial drawings for residential work include exterior perspective drawings, isometric drawings of plumbing systems, and oblique drawings of cabinets.

Receding lines of perspective drawings converge to one, two, or three vanishing points. A perspective drawing is a pictorial drawing with all receding lines converging to vanishing points. Perspective drawings resemble photographs. Perspective drawings may be made with one, two, or three vanishing points. The object may be located above, on, or below the horizon to produce a worm’s-eye, eye‑level, or bird’s-eye view, respectively. The number of vanishing points used and location of the object in relation to the horizon determine the type of perspective drawing. Two vanishing points and an eye‑level view are commonly used for perspective drawings of houses. See Figure 2‑4.

The isometric axes are drawn 30° above horizontal. When sketching an isometric drawing, the isometric axes are drawn and end points for the principal measurements of height, length, and depth are located. Vertical lines are projected from the length and depth end points, and receding lines are projected from the height end point to construct two isometric surfaces. The top surface of the cube is formed by projecting receding lines at the corners. The end points for other lines on the isometric axes or lines parallel to them are located. These end points are connected and all nonisometric lines, circles, and arcs are completed. Object lines are darkened to complete the drawing. See Figure 2‑5.

The oblique axis of an oblique drawing is drawn 30° or 45° above horizontal. When sketching an oblique cabinet drawing, the true shape of the front surface is drawn to scale showing the height and length of the object. Receding lines are drawn to one‑half scale. All measurements along the oblique axis or lines parallel to them are made. Nonoblique lines are drawn by locating their end points on oblique lines. All nonoblique lines, circles, and arcs are completed. Object lines are darkened to complete the drawing. See Figure 2‑6.

The three-view drawing is the most common type of orthographic projection. In an orthographic projection, lines are projected from every corner of the object to be drawn onto an imaginary transparent plane. Three planes are usually sufficient to show all details of most objects. These three planes produce the front, top, and side view of the object. In printreading, the front view is referred to as the front elevation, the side view as the side elevation, and the top view as the plan view. See Figure 2‑7.

Elevation views are related by projection of features from one view to another. Projection lines that connect the parts of one view to another show the relationship of the elevations to the plan view. A transparent isometric box shows the house and indicates the various elevations and plan views. The box is then unfolded to show the relationship of views. Projection lines show that the principal measurements of height, length, and depth are consistent throughout the views. See Figure 2‑8.

A point on an elevation is shown as a line on the adjacent elevation and vice versa. Visualizing the relationship of points from one elevation to another aids in understanding the concept of three‑view drawings. See Figure 2‑9. The simplified pictorial of the tri-level house contains wall surfaces designated A, B, C, and D. Points on these surfaces are designated with lowercase letters a through h. Surfaces A and B are seen on the front elevation in their true shape and size. Surfaces C and D are seen on the right side elevation in their true shape and size. Points on one view are lines on the other view. For example, the point representing the main roof ridge is designated ab on the front elevation. The order in which the letters are presented indicates that point a is closer to the observer than point b. The roof ridge is shown as horizontal line ab on the right side elevation.

An architect’s scale is used to produce scaled drawings. Architect’s scales are read from left to right or right to left depending on the scale. See Figure 2‑10. A 1/4 = 1‑0 scale is read from right to left beginning at the 0 on the right end of the scale. The same set of markings is used for both the 1/4 = 1-0 scale and the 1/8 = 1-0 scale. The correct line in relation to the scale used must be read. For example, 18‑0 on the 1/4 = 1-0 scale is on the line representing 57‑0 on the 1/8 = 1‑0 scale. Inches are read between the 0 and the end of the architect’s scale.

Most tape measures have highlighted portions indicating feet. When reading a tape measure or ruler, the number of feet is determined first. Many tape measures have highlighted areas indicating feet. See Figure 2-11. Next, the number of full inches is determined by reading the last number on the ruler prior to the measurement.

Tape measures and other rulers used in the building trades are often divided into 1/16" increments. Most tape measures and rulers used in the building trades are divided into 1/16 increments. See Figure 2-12. There are 16 equal increments in each inch. Each inch on a tape measure or ruler is divided into 1/16 increments that are indicated with marks of varying lengths. The 1/2 mark is the longest mark between the two full inch marks. The 1/4 marks are slightly shorter than the 1/2 marks and are placed one-half the distance between the 1/2 mark and the full inch mark on either side. The 1/8 marks are slightly shorter than the 1/4 marks and are placed half the distance between the 1/4 marks and the full inch marks and the 1/4 marks and the 1/2 mark. The 1/16 marks are slightly shorter than the 1/8 marks and placed half the distance between the adjoining 1/8 marks.

A tape measure can be used by a tradesworker to measure a component and transmit information back to the architect. Tradesworkers may use a tape measure on a job site to determine a specific detail or to transmit information back to the architect. Each 1/4 space on a tape measure is equal to 1-0 on a print with a 1/4 = 1-0 scale. Each 1/16 space on the tape measure is equal to 3. Therefore, a distance of 1 3/16 on a print represents 4‑9 at the scale of 1/4 = 1'-0. The number of 1/4 spaces must be counted to find the number of feet. This number is added to the number of 1/16 spaces, which represent 3 each to obtain the total of 4‑9. See Figure 2‑13.

Symbols are drawn in proportion to other construction materials. Symbols are drawn to scale to indicate their relative sizes. A symbol is a pictorial representation of a structural or material component used on prints. Walls, windows, doors, plumbing and fixtures, footings, partitions, chimneys, roofs, and other features are drawn in proportion to their size. See Figure 2‑14.

Arrowheads, slashes, or dots may be used to terminate dimension lines. Dimension lines may be terminated by arrowheads, slashes, or dots at the points on a drawing where they meet extension lines. The dimension is placed above the dimension line unless the space is too small. If the space is too small, the dimension is then placed in the nearest convenient space and related to the space by a leader line. See Figure 2‑15.

Walls are dimensioned to facilitate construction methods. Framed, masonry, and other types of exterior walls are dimensioned according to dimensioning standards. See Figure 2‑16. The preferred method for framed walls is to dimension to the outside faces of stud corner posts. Most of the remaining structural members can be located in relation to these rough framing members. It is easier to locate openings for doors and windows if the dimensions start from the outside faces of stud corner posts than if the dimensions are given from the outside face of sheathing since sheathing is applied after the rough openings are located.

Partitions are dimensioned to their centerlines or faces. Interior partitions vary in thickness depending on the structural framing materials and finishes. Dimensions are drawn to the center or the face of a stud partition. See Figure 2‑17. Most common interior stud framed stud partitions have a nominal thickness of 4, not including the finish wall covering. Because of variations that may occur on the job site, the 4 nominal thickness aids in setting partitions accurately. Actual dimensions of a 2  4 stud are 1 1/2  3 1/2. Thus, a partition with 1/2 drywall on both sides is 4 1/2 thick (1/2 + 3 1/2 + 1/2 = 4 1/2). Partitions in bathrooms and kitchens may be thicker to accommodate plumbing soil stacks.

Openings for windows and doors are dimensioned to their centerlines. Locations of openings for windows and doors on the floor plans for frame construction are dimensioned to the center of openings. Locations of openings for windows and doors on floor plans for solid masonry construction are dimensioned to the center of the openings or to the finish masonry abutting the window or door. Dimensions to the centers of the openings are preferred. See Figure 2‑18.