Technical Drawings in Interiors

TECHNICAL DRAWINGS IN INTERIORS 4(1+3)

Lesson 2: Measurement, Scales And Dimensioning

Definitions and Dimensions

The dimension line is a thin line, broken in the middle to allow the placement of the dimension value, with arrowheads at each end.
An arrowhead is approximately 3 mm long and 1mm wide. That is, the length is roughly three times the width. An extension line extends a line on the object to the dimension line.
Dimensions should not be placed in a haphazard manner merely to fill gaps; they must be done in a methodical way and with due thought given to their placement and extent. The first dimension line should be approximately 12 mm (0.6 in) from the object. Extension lines begin 1.5 mm from the object and extend 3 mm from the last dimension line. A leader is a thin line is used to connect a dimension with a particular area. A leader line may also be used to indicate note or comment about a specific area. When there is limited apace, a heavy dot may be substituted for the arrows.

The purpose of dimensioning is to define size and location of the various materials and components.

1. Dimensions should be read across the sheet and are usually placed at the bottom; vertical dimensions must be readable from the right-hand edge.
2. Dimension lines should be set apart from object lines by spacing and line weight so that the chance of their being mistaken becomes minimal; extension lines are taken perpendicularly from the building lines out to the dimension lines. Extension and dimension lines should be kept light in value but should have enough line weight to reproduce in their entirety.
3. All dimensions are placed above the dimension lines and should always be given in feet and inches; the exception to this rule applies to dimensions of less than 12 inches. The draftsperson must decide whether to use 12 inches or the symbols for feet and inches (12” or 1’-0”). Anything larger should be referred to in feet and inches




4. Fractions should be shown with a diagonal slash by which the numbers are separated for greater clarity.
5. All dimensions less than 1 should have a leading zero. i.e. .35 should be written as 0.35
6. There are usually three dimension lines: the line closest to the building should describe its small elements - for example, door widths, and window openings; the second line should carry some of the small dimensions and reflect major features such as a wing, section or offset; the third line (farthest from the building line) should be an overall dimension that will show the total distance from outside face to outside face of the building. Various types of construction will demand slight changes in dimensioning; for instance, wood frame dimensioned from face of stud to face of stud.
7. Dimension lines should be defined by an arrowhead or some other symbol. The arrowhead or other designator should point to an exact extension line. Dimensions are definite measurements from one point to another.
8. Similar dimensions or the same dimensions may be required several times on different drawings. Similar dimensions should, however, never be duplicated on the same drawing. Needless repetition should be avoided.
9. The clarity of the drawing can be improved if extension and dimension lines do not cross. In some instances crossed lines cannot be prevented, but placement should be made with the greatest care possible to obviate confusion.
10. Dimensioning of architectural drawings involves actual sizes, regardless of the scale employed. A note may contradict the dimension given; for example, a 2x4 stud may show a measurement of one and one-half inches (1 ½”) by three and one-half inches (3 ½”).
11. Obvious dimensions may sometimes be eliminated. A door place in a narrow hallway does not necessarily have to be dimensioned, the inference being that the door will be centered.
12. To avoid needless dimensions or crowding, door and window sizes are often eliminated by the use of marks and a scheduling system;
13. Beams and columns are located by their centerlines. A column, for instance, would have a centerline running in both directions.
14. To increase legibility, identical units, spaces, or solids should be dimensioned at one element of the series, and by a note in a specific area should be shown as repetitive. This will eliminate the need to repeat each unit from start to finish of the series. The limits of any series should be marked by showing their extension and dimension lines and arrowhead designators.
15. The dimensional system cannot be left hanging in limbo; it must be tied to tangible usable items apparent in the construction. The building line, or perimeter of the structure, can be used for this purpose. Items are often referenced one to another.