Skip to main content
Al Whitley/3 min read

Understanding Dimensions in Architectural Drawings: A Detailed Overview

Dimension String Hierarchy

Overall Dimensions

Outermost dimensions showing total building width and length.

Module Dimensions

Major divisions (column to column, room to room).

Detail Dimensions

Smaller dimensions showing wall thicknesses, openings.

Tolerance

Note column for construction tolerances if they matter.

Master Blueprint Reading at Noble Desktop

Noble Desktop's Blueprint Reading & Construction Estimating Course teaches reading drawings, takeoffs, and estimating fundamentals.

This lesson is a preview from our Blueprint Reading & Construction Estimating Course Online (includes software & exam). Enroll in a course for detailed lessons, live instructor support, and project-based training.

This tutorial walks through understanding dimensions in architectural drawings: a detailed overview, covering essential tools and techniques for your projects.

Now, let's talk for a few minutes about dimensions. You can see up here that I have an overall dimension of 104 feet 5 inches. What this means is here's my dimension value, this line below it is called the dimension line, so this horizontal is the dimension line, and I have verticals on either end of the dimension line.

I have a vertical over here on the left, I go back to the dimension line, I'm at the text, I go over to the right, I have a vertical here. What this is saying is that it's 104 feet 5 inches from the slash, which is here, I follow the extension line straight down, it takes me to this wall that's right down here, so it's 104 feet 5 inches from the end of that wall to the end of this wall over on the right. So I have my overall dimension string here.

The next string of dimensions typically tends to be major bumps in the building. So you can see that it's 13 feet 9 inches from that same outside wall to the slash, go down to the extension line to the end of the foundation right there, it's 45 feet 10 inches from this slash over to this slash at this wall, it's going to be 24 feet 0 inches from this slash and its extension line right there over to this part of the building here, and it's 20 feet 9 inches to the end of the next building. Now, let's look at the building in a little bit more detail.

Here's what I'd like you to see. Way down in the bottom, I have a legend, and the legend is telling me different kinds of construction. You can see that I have a shaded area, and that's a typical stud wall.

I have my masonry units, which are shown typically as slash marks. I have a dashed line, which we in CAD and BIM terms call a hidden line. I have a hidden line showing line of structure above.

I have a net pattern showing a double 2x4 stud wall, and then I have some perimeter lines of other bits of geometry on the house. So, when I look at the house, you can see that this area over here is the major part of the house. I have the house above, which is shown by this dashed line here, and I have more house over there.

When you look at the drawing, you can see that we have the masonry wall with its hatch pattern. See the slashes in it? We have our typical stud walls, which in this case are wood walls with the darker gray hash inside of it. And if I slide down a bit, you can see that I have my double stud wall happening right down here.

So, let's just zoom in this area a little bit. What I can see, for example, is that it's 3 feet 11 inches from this masonry wall to the corner right here. It's 16 feet 10 inches from this corner here down to this slash right here, which is the outside face of the building.

It's 4 feet 6 inches from the outside face to the center line of the window, and the numbers continue from there. Again, we have the keynotes that are referencing back to the keynote list that's above.