What Are the National CAD Standards, and What Do They Mean to Me?

Periodically, we have clients come to us asking for advice on working with the National CAD Standards (or NCS) because a client requires their drawings to be NCS compliant.
The important thing when working with clients who require compliance, is identifying what parts of the standard they want compliance with. Many organizations think of the layers standards and forget about the rest of the NCS, so may only be looking for compliance with the layer naming portion of the standards. In certain areas, there are options rather than a specific direction, so again, knowing what the client needs specifically is important. The version of the standards is important as portions of the standards have changed and included different options each version. In some cases, the standards aren’t detailed enough for design and need to be extended to support that. The standard has allowances for that. A single requirement statement requiring NCS compliance isn’t really enough due to some of those choices.

What Are the Standards?
The NCS is built from several different standards. The layering guidelines come from the American Institute of Architects. Drawing layout and construction comes from the Construction Specification Institute (their Uniform Drawing System) and plotting guidelines come from the National Institute of Building Sciences. The NCS coordinates these different guidelines into a single package. The National Institute of Building Sciences makes the standards available online through various license packages. The web address is https://www.nationalcadstandard.org/ncs6/index.php.
The NCS consists of several modules that detail various parts of the drawing process. The Modules are:
1. Drawing Set organization – Sheet order, identification, etc.
2. Sheet Organization – Sheet format, title blocks, sizes, etc.
3. Schedules – Guidelines for door, window and other schedules.
4. Drafting Conventions – Process notes for projects.
5. Terms and Abbreviations – Standard terms.
6. Symbols – Standard blocks organized by MasterFormattm divisions.
7. Notations – Guidelines for adding and linking notes.
8. Code Conventions – Regulatory annotations.

The layer standards have their own set of documents, including a Microsoft Excel file with the layering guidelines and a PDF describing how the standards work. The standards basically consist of a discipline indicator, a major and minor group (or two) and followed by a status or phase.
In addition, there are plotting guidelines, Excel sheets for samples and a set of blocks to match the standards.

The Standards and Autodesk
The industry specific versions of AutoCAD (Civil 3D, Architecture, MEP, etc) include templates with NCS layers (technically AIA layers) implemented. For example, Civil 3D includes the Autodesk Civil 3D (Imperial) NCS.dwt template which includes an implementation of the layers, complete with a number of layer descriptions filled out.

The challenge is there are no status indicators. For example, existing layers should include a status indicator to segregate new from existing or objects to be demolished. So that could potentially multiply the number of layers substantially. And of course, with Civil 3D, the BIM objects are managed as objects, such as surface, so the sub objects like contours, are dependent on the style definitions. So the surface itself may need to be on C-TOPO-D (to be demolished) or C-TOPOP-N (new work). The organization then decides whether it is necessary to create styles differentiated by status as well.
 
   

The need to explode the drawing to AutoCAD and remove the BIM objects would necessitate styles with layers detailed with that differentiation.
In the way the layers guidelines are applied to different projects or organizations, the same types of questions and answers should be generated for the other modules. For example, the sheet identification. The sheet organization describes methods and options for numbering sheets, but only addresses design sheets, and doesn’t address models or data references. Does the project require Level 2 discipline identifiers (ET for Electrical Telecommunications) or just the Level 1 (E for Electrical)?
Ultimately, the requirement to comply with NCS standards should be the start of a conversation and being familiar enough with the standards so you can address these questions can save a lot of time trying to figure them out during the design or save some heartburn during submittal. In the end, the goal is to get the design date integrated in with existing, operational data, and the standards are the key to migrating data from multiple sources.