What do Architectural Lines and Lettering mean?

The architectural lines and lettering come under drafting that is a universally recognized graphic language by a draughtsman, the architect, engineers, and so on for technical drawings and specification detailing like lines, dimensions, and so on.

Rules and guidelines for line mechanical drawing

Lines on a drawing should be of the best high-definition quality with a clear end product. Neatly and properly drawn lines are dark, crisp, sharp, and of a uniform thickness. There must be no modification in darkness, only a thickness variation is acceptable that is known as a line contrast.  The variation in sizes of lines has a certain identification purpose for each. It is mandatory to follow the set rule for the recommended line thickness, which is expected to be thoroughly defined in manual drawing than in architectural drawing or drafting.

Before commencing the mechanical drawing, make a note that the initial guidelines or construction lines must be as light as possible and straight lines since they are primarily used for making rough shapes and drawings, floor plans, guide marks for letter heights, basic drawing layout, and are temporary in nature. After the drawing is finalized, these lines should be typically invisible but suggested to be slightly visible for any changes to be done in the future.

A 4H to 6H pencil or a 0.3 mm lead pencil is advisable for perfect guidelines.

Types of lines (with respect to their thickness)

Bold lines

These are very dark with thick breadth. Usually seen in wall lines of the floor plan views and other views, perimeter outline of a 3-dimensional isometric or oblique projection diagram, and so on.

Use a soft B to 2B pencil or a 0.5 mm or 0.7 mm lead pencil.

Medium lines

Certain objects which include furniture or items inside the 2-D design of the floor plan or the 3-D design should be drawn using medium lines as well as the labeling of all the graphics on the layout.

Use HB pencil or a 0.5mm lead pencil.

Light lines

Lines that depict the direction of any moving structure, information lines, patterns like hatch patterns for sections, and fill patterns must be drawn with light lines.

Use an H to 2H pencil or a 0.3 mm or 0.5 mm lead pencil.

Border lines

They provide the margins of the drawing as well as the outline of the bottom right nameplate or personal details block. Twice as thick as compared to bold lines recommended.

Use a 2B to 4B pencil or a 0.7 mm to 0.9 mm lead pencil.

Types of lines (with respect to their variations)

Solid lines or object lines

They indicate visible objects, leader lines, and dimension lines.

Dashed lines (hidden lines)

They are used to depict the characteristic features that are not visible when seen from a particular angle. These lines are thin and usually drawn about 3 mm to 10 mm in length with a spacing of 1.5 mm to 3 mm between the dashes. The dashes must be kept equal in length on the drawing. It takes some practice to manually draw dashed lines and judge the uniform length of each dash.  Recommended leads for manual drafting are a 0.5-mm lead pencil with 2H or H lead, or a sharp pencil with 4H, 2H, or H lead.  Examples of dashed-line representations are beams, headers, kitchen cabinets, and so on in the layout design.

Extension and dimension lines

Extension lines show how much extent a dimension can go. The length of the dimension is seen by the dimension lines and at the edges, we can see a slash, arrowhead, or a dot closure. Arrowheads must have sharp terminals and darkened heads. The dimension numbers are typically kept above or at the center of the dimension line. Extension lines initiate with a short start distance but run beyond the last dimension line. For instance, when we give dimensions to the door’s center then its centerline becomes the extension line. Extension and dimension lines are usually thin, dark, crisp lines that are drawn with a 4H, 2H, or H lead and a 0.5 lead pencil.

Leader lines

Leader lines are also thin, dark, crisp lines. These lines are required for connecting notes that are in relation to the drawing features. They can be drawn freehand or a curve stencil can be used.

Break lines

Break lines are useful for instance to deduct a portion of something, depict a partial view and reduce the length of a long object. Two types of break lines; The long break line is generally drawn in architectural drafting and uses a break symbol drawn freehand.  The short break line is an irregular line drawn freehand and is used for a short area that is applied to some architectural reference designs. The short break line has a minimum usage in architectural drafting than the long break lines.

Center lines

Used to indicate center or axes of any view or objects respectively and if two centers intersect each other, usage of short dashes at the junction is advisable.

Section lines

Imagine the object or feature being cut, that is the section line. It also comprises arrows that show the direction from which the cut section needs to be seen.

Lettering or Text depiction

The letters or the text used must be precise, readable, and legible for seamless reading without any confusion to the reader. Poor lettering or text demonstration may even ruin the best of the drawings. These artistic text styles are typically used by architects, drafters, and designers. With the emergence of CAD, various architects prefer a computer-produced font style or text.

The following is the basic terminology commonly related to lettering:

  • Composition: It indicates to layout, spacing, and overall image of the drawing.
  • Alignment should be justified: This helps in bringing the text into a set framework from both sides.
  • Lettering: Used for handmade drafting of letters and numbers whereas the text is the term for lettering that is inscribed using CAD. 
  • Font: It is a style used for the text to give an aesthetically pleasing look.
  • Text style: It is a character set that contributes to the font, height, width, and angle of the text and the drawing layout.
  • Alphabet annotation accepted by architects must be of the same size, font, and height throughout.

Types of lettering (mechanical symbol drafting)

  1. Single-Stroke Lettering
  2. Slanted Lettering

Rules and guidelines for text and lettering mechanical drawing

  • Annotation for foot and inch units must be (‘) and (‘’) respectively.
  • All the dimensions and values in architectural layouts are in millimeters (mm) generally.
  • Make a note that all the metric values must be in lowercase. Exceptions are the SI units like K, Pa, and so on.
  • For unit short-forms, use vertical text and space should be left between numbers and the SI units like 60 kg, 40 mm, and so on.
  • No space between the units like ‘k g’, correct is ‘kg’. Also use either symbol (e.g., ‘m’) or full names (‘meters’).

Types of Text (CAD Software)

  1. Arial font
  2. Times font
  3. Country Blueprint font
  4. Stylus BT font
  5. San serif font
  6. Romans font
A specimen sheet by William Caslon shows printed examples of Roman typefaces.
CC 1.0 | Image Credits: https://en.wikipedia.org | William Caslon

Context and Applications

The topic is taught in courses related to:

  • Bachelors in Technology (Civil Engineering)
  • Masters in Technology (Computer Aided Drafting)
  • Masters in Science (Structural Engineering)

Practice Problems

1. An H to 2H pencil and a 0.3 mm or 0.5 mm lead pencil is used for which type of lines?

  1. Bold lines
  2. Medium lines
  3. Light lines
  4. Border lines

Correct option- c

Explanation: An H to 2H pencil and a 0.3 mm or 0.5 mm lead pencil is used for a light type of lines.

2. Which one of the following is/are the type(s) of line with respect to its variation?

  1. Solid and dashed lines
  2. Extensions and dimension lines
  3. Leader and break lines
  4. All of these

Correct option- d

Explanation: The type(s) of line with respect to its variation are solid lines, dashed lines, extensions, and dimension lines, leader lines, and break lines.

3. Which of the following is a type of text style used in CAD?

  1. Single stroke
  2. Times font
  3. Slanted
  4. None of these

Correct option- b

Explanation: Times font is a type of text style used in CAD.

4. Which line shows that a view or an object is being cut to see the inside hidden cross-sections?

  1. Section line
  2. Center line
  3. Break line
  4. Dashed line

Correct option- a

Explanation: The section line shows that a view or an object is being cut to see the inside hidden cross-sections.

5. What is the annotation accepted legally by an architect, designer, or publisher?

  1. 25 mm
  2. 4 km
  3. 6 feets
  4. 6’

Correct option- d

Explanation: Annotation accepted legally by an architect, designer or publisher is 6’ (6 feet).

  • ASME (American Society of Mechanical Engineers)
  • Architectural graphics
  • Georgia serif typeface

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