Sometimes, the simplest concepts in the CAD world are overlooked by instructors. We are so used to some concepts that we never even discuss them. That's often the case with drawing layout: those of us in the industry do it so often that it's second nature to us. in our mind it doesn't even require conscious thought. For anyone new to the CAD world though, it's a vital concept that requires some explanation. Hence, this article! These concepts apply to all CAD systems, whether your using AutoCAD, MicroStation, or any other CAD package, the concepts here are a must for you to become comfortable with.
Determining which scale to use for a particular drawing is the key to developing a complete set of construction documents. The primary factor to consider when beginning is sheet size: which size paper will enable you to present your design information at a readable size and in the most cost effective manner? The best way to calculate this is to take into consideration the size of your site/structure and how much of it can be displayed at what scale on a particular sheet size. For example: if you are drawing an architectural floor plan of a building that is one hundred fifty (150’) feet in length, and you’re considering presenting it on a 24” x 36” sheet of paper, a quick calculation of the sheet length, divided by the scale, tells you how many sheets of paper you are likely to need. In this case, if we use a 1/4” = 1’-0” scale, and we have an available 34” of horizontal drafting space (you need to leave an inch or so on each side for margins) that gives us the ability to draw 136’-0” of our building on one sheet (34/.25 = 136). This isn’t enough to show the entire building, so you need to decide whether to show the design on two separate plans with a match line, use a different drawing scale, or a different size sheet of paper. The determining factor here is usually cost. The fewer sheets of paper used, the less cost is involved with reproduction of the design drawings later on. Using the example above, if we choose to use two sheets at the 1/2” = 1’-0” scale, we double the reproduction costs. We could use a 1/8” scale instead, which lets us draw 272’ of building and stay on a single sheet (34/.125 = 272) but that scale might be too small for us to effectively annotate all the information we need to show. The last option is to use a larger sheet, such as 30” x 42”, which costs more that a single 24” x 36” but certainly less than using two sheets. With a 30” x 42” we can still use our 1/4” scale on a single sheet of paper (40/.25 = 160) and show up to 160’ of building length. We would also need to consider the vertical dimensions of the site/structure in exactly the same manner to determine what scale and sheet size to use.
You also need to consider the shape of your site/design when deciding which size sheets to use. If you are constructing something that has much longer horizontal dimensions, you’ll need to make use of sheet sizes with as much horizontal space as possible – 30” x 72” for example. If your design is more vertically oriented, you’ll want to use a taller sheet for your design. Depending on what type of output device you are using you may have the ability to print in either Portrait (vertical) or Landscape (horizontal) modes, which will allow you to make use of different orientations and/or sizes in order to display your design in the most efficient manner.