The National CAD Standard version 3.1 is a consensus standard compiled from three existing standards and guidelines by NIBS (The National Institute of Building Sciences). These consist of the AIA Layer Guidelines version 3.0, the CSI Uniform Drawing System (UDS) and the Tri-Services Plotting Guidelines. The National CAD Standard v. 3.1 is supported where possible in AutoCAD Architecture 2021 toolset through the use of pre-configured Layer Standards, Layer Key Styles, plot style tables and annotation tools. While it is not required that custom content be compliant, when creating new content for use in the United States you should take this support into account.
The Imperial templates provided with AutoCAD Architecture 2021 toolset are pre-configured to load the AIA Version 3 Layer Key Style by default. This is based on the AIA Version 3 Layer Standard, which is in turn compliant with the AIA Layer Guidelines version 3.0.
The AIA v3 Layer Key Style includes line weights and linetypes that are in accordance with the Uniform Drawing System, and the colors that it specifies are compliant with the Tri-Services plotting guidelines. Additionally, the drawing default display representations for all objects in the template files have been configured to adhere to the Tri-Services Guidelines and Uniform Drawing System recommendations by assigning appropriate colors, linetypes, line weights and plot styles to all display components.
There are twelve templates that are provided with the AutoCAD Architecture 2021 toolset sold in the United States, and each one is pre-configured to use a specific plot style table:
| Template File Name | Description | Default Plot Style Table |
|---|---|---|
| AEC Model (Imperial Ctb).dwt | Used for model drawings with imperial (architectural) units and set up for color-based plotting. | AIA Standard.ctb |
| AEC Model (Imperial Stb).dwt | Used for model drawings with imperial (architectural) units and set up for named plot styles. | AEC Standard.stb |
| AEC Sheet (Imperial Ctb).dwt | Used for plot sheet drawings with imperial (architectural) units and set up for color-based plotting. | AIA Standard.ctb |
| AEC Sheet (Imperial Stb).dwt | Used for plot sheet drawings with imperial (architectural) units and set up for named plot styles. | AEC Standard.stb |
| AEC Model (Metric Ctb).dwt | Used for model drawings with metric (decimal) units and set up for color-based plotting. | AIA Standard.ctb |
| AEC Model (Metric Stb).dwt | Used for model drawings with metric (decimal) units and set up for named plot styles | AEC Standard.stb |
| AEC Sheet (Metric Ctb).dwt | Used for plot sheet drawings with metric (decimal) units and set up for color-based plotting. | AIA Standard.ctb |
| AEC Sheet (Metric Stb).dwt | Used for plot sheet drawings with metric (decimal) units and set up for named plot styles. | AEC Standard.stb |
| Structural (Imperial Ctb).dwt | Used for structural model drawings with imperial (architectural) units and set up for color-based plotting. | AIA Standard.ctb |
| Structural (Imperial Stb).dwt | Used for structural model drawings with imperial (architectural) units and set up for color-based plotting. | AEC Standard.stb |
| Structural (Metric Ctb).dwt | Used for structural model drawings with metric (decimal) units and set up for color-based plotting. | AIA Standard.ctb |
| Structural (Metric Stb).dwt | Used for structural model drawings with metric (decimal) units and set up for named plot styles. | AEC Standard.stb |
In addition to the default plot style tables assigned to the imperial and metric templates, there are several additional optional tables provided. Many of these are for use with older legacy templates and drawing files:
| Plot Style Table | Description |
|---|---|
| AEC Standard.stb | Default plot style for templates using named plot styles. This table uses generic names for plot styles and passes line weight control to the layer and object properties. All objects plot black. |
| AIA Standard.ctb | Default plot style for templates set up for color-based plotting. This table maps each color to an explicit line weight according to the Tri-Services guidelines. |
| AIA Standard Color.ctb | Optional plot style for templates using color-based plotting. All colors are mapped to explicit line weights according to the Tri-Services guidelines. Colors are controlled by the objects and layers. |
| AEC Standard Color.stb | Optional plot style for templates using named plot styles. This table uses the same names for plot styles as the AEC Standard.stb plot style table, but objects will plot according to their AutoCAD color. |
| AIA Standard.stb | Legacy plot style for older templates using named plot styles. This table includes plot styles named according to line weight definitions specified in the Uniform Drawing System. |
| AIA LWT by Object.ctb | Legacy plot style for older templates using color-based plotting. All colors are mapped to black and line weight control is by layer and object properties. |
| AIA LWT by Object.stb | Legacy plot style for older templates using named plot styles. All line weight control is by layer and object properties. |
| AIA Standard Color.stb | Legacy plot style for older templates using named plot styles. Plot styles assign line weight explicitly. Colors are controlled by objects and layers. |
| AIA Color LWT by Object.ctb | Legacy plot style for older templates using color-based plotting. Color and line weight control is by layer and object properties. |
| AIA Color LWT by Object.stb | Legacy plot style for older templates using named plot styles. All plot styles assign color and line weight according to object and layer assignments. |
Legacy named plot style tables have seemingly redundant plot style names that correspond to UDS line weight names. Many of these tables use the same plot settings for multiple plot styles. This was done to allow for consistency in naming when switching between plot styles. With the newer AEC Standard.stb plot style tables, this complex plot style naming has been abandoned in favor of a much more simplified system. Both the AEC Standard.stb and the AEC Standard Color.stb plot style tables use the same plot style names, however the former will plot all objects black while the latter will plot all objects according to their AutoCAD color. Aside from color vs. monochrome, the plot styles determine saturation:
The Uniform Drawing System also specifies formatting for symbology and annotation. This is supported in AutoCAD Architecture 2021 toolset through the content provided in the Documentation Tool Catalogs and in the drawing templates themselves.