Explore the basics of dimensioning in technical drawings, including the key components and variations between architectural and engineering styles. Learn about the role of extension lines, dimension lines, and indicators in creating clear and accurate dimensions.
Key Insights
- Dimensioning in a technical drawing always involves an object, extension lines that extend beyond the dimension line, and a gap between the extension line and the object. An indicator, such as a slash, tick, or arrow, marks where the extension line and the dimension line meet.
- Architectural and engineering drawings can be distinguished by their dimensioning styles. Architectural drawings often use a tick as an indicator and position the dimension text above the dimension line, while engineering drawings typically use an arrowhead and place the text midway between the arrow lines.
- Dimensioning practices are similar for both horizontal and vertical dimensions. In architectural dimensions, however, the dimension text is rotated 90 degrees counterclockwise and is always readable when tilting the head to the left, regardless of whether the dimension is pulled from an object to the left or right.
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Let's spend a few minutes talking about dimensions, and we will use this example up here as our first discussion topic. You can see that when we dimension, we always dimension to an object, and what we're seeing is that it's three feet from the end over here to the end over here. Now let's look at the actual components of the dimension.
Again, I dimension to an object, I have an extension line that has a bit of a gap between the object and the extension line, which is this entity right here. So it's going from the end of this object, a bit of a gap, the extension line goes up and extends beyond the dimension line. So here's the dimension line, there's an extension line here, and another extension line here.
Where the extension line and the dimension line come together, there is usually an indicator, which in this case is an architectural tick or a slash. If we look down here, we can see that they've chosen to use an arrow instead. So again, with the dimensions, we dimension to an object, so we have where we're dimensioning from, we have an extension line, another extension line, there's the dimension line, there's the indicator, a slash, a tick, or an arrow, and here is the dimension text, which is saying three feet dash zero inches.
So this would probably be an architect's drawing because I'm seeing an architectural tick here. So you can see I have a tick and I have the text above the dimension line. Down here, this is probably from an engineer's drawing because instead of using the tick, they're using the arrowhead, and the text is located midway between the arrow lines.
So these are both horizontal dimensions. If we look at this example, this is a vertical dimension. Essentially, the dimension elements are the same.
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We have the object, extension lines, and a dimension line. This is an architectural dimension, so we still have our ticks or slashes. The dimension text is still above the dimension line, but rotated 90 degrees counterclockwise.
If you look at the floor plan, you will notice that the dimension text is always rotated counterclockwise, so that when you tilt your head to the left, you can read the text. This is the same if the dimension is pulled from an object to the left, like here, or from the right, like here.
