Construction drawings convey information through line drawings. In this video, Jim explains the various types of lines and line styles used on a construction drawing, and discusses the meaning of each line type.
- [Instructor] Understanding what the different lines on a drawing represent is really one of the key factors in being able to interpret the information that these drawings of trying to convey. So, throughout these course, we'll look at different views, details, and cross-sections and I'll make sure I point to different type of lines and symbols in our set of drawings and talk about what they mean as we progress, but what I want to do now is I want to start on this projects foundation plan on sheet A-102 to introduce you to some of the different lines and symbols that you might see on a typical set of construction drawings so we can talk about what they mean.
Now, for future reference as we progress through this course, we've also provided you with a separate exercise file of what some of these line types represent. So, for now, let's go ahead and zoom, again, remembering from our last video, to go to the title block and see what the sheet number is and the fact that it tells us that this is the foundation plan, so, I know that I am starting in the correct place, and what I want to do is this gives us an overview of the foundation for this project and, again, this project consists of this house.
It has a freestanding porch here and is connected to a separate garage here, so that's what we're going to build on this project, and what I want to do is zoom in to the house just a little bit and start to pick apart a lot of this information and a lot of these lines that this drawing is showing us. So, the first thing I want to look at are some notes and legends and keys. So, when I zoom in I see a lot of notes that say S6, S6, S6, and so on and those notations are inside of a rectangle, so, what I'm really looking for is a key that tells me what a note inside of a rectangle means.
Above it, you'll see another key that is not used on this particular sheet that would be a letter or a number inside of a hexagon and we'll look at some examples of where that's used in some future videos but for now, I want to know what this S6 means. So, I come over to the key and I can immediately see that S6 is a condensate drain. If I go back to my drawing, again, look at the S6, I see a little circle, that must be the condensate drain, and I also have some text here that says, yes, indeed, this is a condensate drain and you can see that I also have what's called a leader line coming from that call out down with an arrow pointing to that drain.
Now, below that, again, for this drain, which is an S2, or floor drain, I have some specific dimensions that tell me where to put that drain in this floor and, I want to zoom in so you get a good idea of where these dimensions start and stop, so, I have a dimension of nine foot four inches and underneath that I have the dimension line and if I take the dimension line and look at this little intersection symbol and follow the extension line up to where it stops, I can see that this nine foot four dimension is measured from the outside edge of this foundation wall.
If I follow the dimension line in the other direction and its extension line down to the floor drain, I can see that the dimension in this case is to the center line of that floor drain. So, this is something that's really important as you progress through your set of drawings and start to lay things out in the field, you really need to take a close look, zoom in if you need to, and see where these dimension lines start and stop so you understand whether they're measuring from the edge of a wall or the center line of a wall, or, in this case, the center line of that floor drain.
Let's go ahead and zoom back out and scroll over so we have our garage in view and there's just a little bit less information on the garage here, so, it's a little cleaner as we continue to look at some of the line types. So, again, this is the foundation for the garage and I have here a solid line that's actually with some shading in it that goes around the perimeter of the garage and since this is happens to be my trade, I used to be a concrete guy, and this is a concrete foundation, so, I know that this shading is typically used by designers to indicate concrete and if I look up here at the top we'll see in fact that, yes, this is a six inch wide concrete garage foundation wall and you can, again, see the leader line pointing to that and indicating that this is a six inch wide concrete wall.
This is a solid line which really tells me that this is some work that is going to occur on this level or this floor level that I'm currently working on right now. Next to that, you'll see a dashed line or some people refer to this as a hidden line. Anytime I have a dash line, that generally tells me that there's something underneath the level that I'm currently working on and, in this case, if I follow the Leader line up, I have another notation that says this is a two foot wide concrete footing and the dash line would indicate that that footing is underneath the foundation wall.
So, I'm going to go ahead and insert a picture that I clicked out of our detail sheet and we'll look at detail sheets later but, for now, I want to put this detail next to these notes so we get a clearer view of what these lines really tell us. Again, the dash line that indicates a two foot wide concrete footing is shown here and the solid line that indicates the six inch wide foundation wall is shown on top of that footing.
So, as we progress through these drawings, we'll talk about the difference between plan views and cross-section views but, basically, I'm looking at this footing and foundation wall in a plan view from the top and in this detail I'm looking at it as a cross-section from the side and I get a little clearer indication of what the two foot and six inch dimensions mean and the fact that this dash line is showing me something that is below grade. Now, speaking of grade and elevations, I have another notation here that can help me figure out what's going on on this particular drawing.
Anytime we see this symbol, that is a universal symbol that tells me that they're trying to give me an elevation or a height and, in this case, if we zoom in so we can really see what this means, it says the top of the garage foundation wall is at elevation minus five inches. Let's put that in perspective and zoom over to the house where it says the top of the house foundation wall is at elevation zero. So, in this case, that's just what they used as their starting point.
They're going to say that the top of the house foundation is the zero point and the top of the garage foundation is five inches below that. Again, let's look at these lines and what they're telling us a little bit more. As we follow this around, we see that the shading inside these solid lines goes away, comes back, goes away again, and so on throughout this perimeter. Now, if I look at this elevation note, I see that in this section where it's not shaded, it indicates that that elevation is minus two foot eight inches.
So what that tells me is that the foundation wall at this point is two foot three inches shorter than the foundation wall around the perimeter of the garage and, since I understand that this is a garage and I know I have to pull cars into it, that kind of makes sense, I can start to see that this is maybe where the cars can pull in. Now, while we're looking at these line types, I want to go ahead and click through and look at the next two or three sheets in this set to show you how these line types change.
So, if we go to the next sheet, this is the basement plan and my hidden line showing the footing is underneath. I would need to start with the foundation plan to know that there's a footing underneath here. If I click and go to the following plan which is my framing plan, you can see I start to put some walls on top of my foundation wall and, as we progress through here, now I start to get a shaded line around here and I get a really good indication of where walls are, where windows are, where doors are, and the fact that, yes, this is probably where the cars pull into this garage.
So, let's zoom back, and look one more time at our dimensions and, again, I just want to emphasis how important it is that you understand what are these dimensions, so, in this case, this one is two foot three quarter inches, you need to follow the leader line down, or the extension line, in this case, down, and make sure you understand whether they're dimensioning to the edge of the wall or the center line of wall and different designers will do that differently, you just need to make sure you follow what the design tells you, so that you get these walls in the correct place.
If you follow the extension line, in this case, the other direction, you'll see that this one goes to a notation that is an E and this one leads to a notation that is an E.1 and, just for further explanation, if you follow that line across, you'll see that that is actually dimensioning to the center line of what will be these columns that hold up that porch between the house and the garage. So, we'll look in a later video at what these reference points means for us and how they can help us but the point that I want to leave you with in this video is to really understand where these dimension lines start and stop and what the lines are actually pointing to.
So, again, I know there's a great deal of information on these drawings, I know they can get cluttered, just remember a few key things. Sometimes, for one, the information on these drawings will contain abbreviations that you don't understand, so, I skipped right through this one, I read this as top of garage foundation. Again, I'm familiar with these drawings, I'm familiar with some common abbreviations in the industry, TO just stands for top of. There's not anywhere on this drawing that you're going to find that spelled out. Now, in other cases, if we scroll back over here and look at this line and this line, I have a notation that says CJ.
Again, I'm a concrete guy, I know that CJ stands for control joint, but if I didn't, sometimes you can scroll around and the designers are nice enough to spell out what CJ stands for the first time and other times they're just not going to and if you don't understand what the abbreviation means, you might just have to ask, especially if you're looking at drawings for work that is not your trade or that you're unfamiliar with. So, learn also to compartmentalize the information and pick out what pertains to you versus what pertains to other trades and then understand that these drawings come as a set and, as I showed you, you might have to flip through multiple pages and look at different views or details to figure out what's going on and what these lines really mean and that's how we're going to progress through the rest of this course as well, really, with each video building on the previous one and learning how to find different views to help us interpret the information being shown.
So, before we look at those views, though, let's go ahead and go to the next video and discuss these dimensions a little bit more.
In this course, learn how to read construction drawings. Jim Rogers helps you acquire this important skillset by taking you through the different components that make up construction plans, and helping you understand the language of construction drawings. He covers types of views, highlights different kinds of construction drawings—including architectural drawings, electrical drawings, and plumbing drawings—explains how to read general notes, and more.
- Deciphering the language of construction drawings
- Understanding line types
- Reviewing plan views, elevation views, section views, and isometric views
- Reviewing architectural drawings, structural drawings, and mechanical drawings
- Drilling down to the details
- Reviewing reference points on drawings
- Understanding schedules
- The future of construction drawings