Ask an Architect
What Different Line Types in Architecture & Design Drawings Mean
Thick lines, thin lines, lines with short or long dashes (or both!) — if you don’t speak the language of all these line types, an architecture or design drawing can be pretty mystifying. This primer on design drawing linework will give you a starter toolkit so you can tell what you’re looking at.
July 16, 2020
Dashed lines, solid lines, ones with dashes and dots, thick ones, thin ones… What do all these lines mean?
Have you ever heard someone talk in a jumble of letters and have no idea what the heck they mean? Well, we hate using acronyms, as they do a lot to make other people feel, well, not so smart. No one likes feeling like they have no idea what is going on. In the same respect, reading an architectural drawing is something that can be incredibly confusing to people who don’t know what the heck they’re looking at. Just like speaking in acronyms can sow confusion, we’ve found that when we show an architectural drawing to a client, they often don’t know what they’re reading, and conveying a design concept can be muddled by the fact that they just don’t quite know what they’re looking at.
So, in the interest of helping people understand what an architecture, interior design, or landscape architecture drawing is communicating, here’s a quick primer on what those pesky lines signify. We’ll note, though, that there are going to be exceptions to the rules here, and not all architects are the same. But most architects and designers are generally following these rules. We’ll also add, that if you don’t understand what something is you should absolutely feel OK asking, “What does this line mean?”
Solid Versus Dashed or Dotted Lines
The first and most basic rule of lines in design drawings is that solid lines indicate visible or “real” objects or surfaces, while anything drawing with dots and/or dashes indicates something that is unseen or “hidden” from view. Lines can represent different things depending on what “view” you are looking at — for example, are you looking at the face of one wall of your room and you see lines that represent a window? That’s an “elevation” view. Or are you looking at the floor and you can see lines that represent all four walls of your room? That’s a “plan” view. In both cases, the solid lines indicate the boundaries of what you are looking at.
Solid Single Line
In a plan view, a solid single line is usually something like the edge of a cabinet, a floor threshold, the nosing of a stair, or the edge of a tabletop. It isn’t a wall (read more about what walls look like below). In an elevation view, a solid line is something that has an edge or a corner, like a cabinet or a window frame or door jamb.
Solid, Single Lines Viewed in a Floor Plan
Usually, this type of line is indicating something that is an edge, such as the edge of a stair or the edge of a countertop.
Solid, Single Lines in Elevation Views
Like in a plan view, solid lines usually indicate things that are edges, like the edge of a window or the edge of a cabinet.
Two Solid Lines with a Hatch or Shaded Fill
This is a wall, and it only shows up like this in plan views. The hatch or shaded fill inside the wall varies per architect or designer, and there should always be a legend that explains what that hatch or shade represents. Typically, we will show an existing wall with a light gray shaded fill in between the lines, and show new walls with a dark gray shaded fill in between the lines.
Pairs of Solid Lines with a Shaded Fill in a Floor Plan
These pairs of lines indicate walls. If there are only two lines, they indicate the surface of the wall finish on each side of the wall. If there are other, thinner lines within the hatch or shaded area, these can indicate some of interior components that make up the wall.
A Short-Dashed Line
In a plan view, we denote a short-dashed line as something that is above what you can see in the rest of the drawing. A floor plan is actually a representation of a house if someone basically sliced the top of your building off at 4 feet above the floor, and then drew what they saw remaining. When that happens, there are things — like upper cabinets, or big, trimmed out openings above a pass-through between rooms — which you can’t see when the top half of your building is cut off. To convey these things, as they’re important to know that they’re there, they are shown with a short-dashed line.
Short-Dashed Lines Viewed in a Floor Plan
Lines made of short dashes in a plan view indicate things that are overhead, or rather, over the height at which the plan was “cut” — usually things above about 4' from the floor.
Short-Dashed Lines in an Elevation View
In an elevation view, these short dashed lines are usually indicating something you can’t see. In the plan view, you couldn’t see them because they were above the view plane. In an elevation view, you can’t see the things because they are behind doors, or otherwise hidden from view.
A Long-Dashed Line
A different type of dashed line (and it isn’t always consistent between design firms) can show things that are slightly different than a short-dashed line. In a plan view, a line with long dashes is often something that is much higher above you than something that would be shown with a short-dashed line, like the eaves of a roof. These can be helpful for reference and are called out in a different line type than their shorter-dashed sibling.
In an elevation view, long and short-dashed lines are usually depicting different elements that are all hidden from view, like shelves behind a cabinet door and a microwave sitting on that shelf. But they can also be used to delineate spaces that are “open” and not to be confused with a solid wall.
Long-Dashed Lines in a Floor Plan
Lines composed of longer dashes also show things that are above the view, but are used to show things that are much higher, like the eave of a roof overhead.
An Alternating Long and Short Dashed Line
This alternating long and short dashed line has a name, a centerline. This line is not “real” per se, it indicates the exact center of whatever it is passing through for purposes of alignment and spacing.
For example, you might see a centerline passing through a doorway or a toilet to indicate the location of these objects in the context of their surroundings. Sometimes (as with a toilet shown in a plan drawing) it has round edges, and the symbol for it in the drawing is a stand-in for the actual toilet. If its location is designated by the centerline of it, rather than a side edge, these small variations are accounted for.
A Line with Alternating Short and Long Dashes
These are centerlines, and they can show up either in plan or elevation views. They mark the centers of objects for the sake of locating them for construction.
In other cases, like the doorway, it could be that the most important thing about the location of the doorway is that it is centered in the room. Indicating how far the door jamb is from the corner of the room might not end up with the desired results, especially if the width of the opening changes during construction, whereas indicating its centerline is oriented in the room will.
This line can also be accompanied by the CL symbol, which is a helpful reminder of “Center Line” written in a fancy shorthand.
A Single, Curved Line Forming Part of a Circle
This is easily the one that I most often forget to explain to clients and a lot of people (you’re not alone!) have no idea what this means! It is usually drawn as a solid line (although some architects draw it as a dashed line) and conveys where the door will swing. This is shown to help convey how the door swings to the contractor and to ensure that the door, as it swings, won’t smack into something.
Arced Lines in a Floor Plan
These arcs are attached to the end of rectangles that represent doors. The arcs are tracing the swing of the door as it opens, from the edge of the door to the jamb.
Thicker vs. Thinner Lines
Is the line thin or thick or somewhere in between? Back in the proverbial day, when drawings were done by hand, the thickness of your lines helped convey the importance and hierarchy of what was depicted in the drawing. As we have moved into 2D and now 3D drawings, the weight of a line still conveys hierarchy. Typically, a thick line is either something closer to you (like in an elevation or building section), or is something more primary, like the edge of a wall in a plan. A thin line is either something farther away or something less important. This helps your brain understand and translate what you’re seeing.
Sometimes, clients already know what they’re looking at, but — we figure — better safe than sorry. Besides, like we said, not all design teams follow these rules exactly, so what you might have understood in years past working with another designer might not always translate perfectly. When in doubt, just ask. We always appreciate it when clients ask us questions!
