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Unit 5: Understanding Layers and Linetypes

Overview

Correct use of layers and linetypes is a fundamental aspect of any architectural CAD draw-ing. The American Institute of Architects (AIA) has developed a standard for organization and naming of layers for CAD. In this unit you will learn about the AIA layer naming standard, and also the ANSI linetype standard. You will then apply these principles to the template drawings you created in the previous unit.

Objectives

• Create layers using the AIA naming standard.• Create linetypes following the ANSI standard.• Load linetypes following the ANSI standard and assign them to layers.• Create C and D size template drawings using the AIA and ANSI standards.

Introduction

In architectural CAD drawings, proper use of layers is essential. In many projects several dif-ferent drafters may work on the same drawing. One drafter may be responsible for geometry creation. Another may be responsible for dimensioning. Proper naming of layers is essential in all CAD drawings to ensure standardization in a company. The American Institute of Archi-tects has established standards for layer names in their publication CAD Layer Guidelines. This publication may be purchased on-line at:

http://www.cadinstitute.com/

Along with layers, there are also standards available for linetypes. AutoCAD contains a pre-defined alphabet of lines, including several that conform to ISO standard linetypes. ANSI also has standards available for defining linetypes.

Section 1: Working With Layers

Standardizing layer names and content is an extremely important aspect of CAD drawing. In a typical architectural drawing, you may easily have over 100 layers. You may, for example, have separate layers for symbols, walls, plumbing, electrical, HVAC, and dimensions. Com-mercial standards are available, such as those defined by the American Institute of Architects (AIA).

Without standardization, it becomes virtually impossible to have different people work on a project. In many cases the geometry you create may be used in several different places. The floor plan may be used to create an electrical and plumbing plan. Symbols may be used to represent doors and windows, and then obtained from the drawing to create a bill of ma-terials. Imagine trying to determine which layer contains a specific door symbol from a list containing over 100 layer names!

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Naming Layers

The structure of an architectural drawing is normally defined in the standards of a firm. A com-mercial standard exists that was developed by the American Institute of Architects (AIA).

Principles of the AIA Layer Naming Format

The AIA layer guidelines are organized as a hierarchy. The two formats offered for defining layer names are a long format using 6 to 16 characters, and a short format using 3 to 8 char-acters. While either format is acceptable, consistency should be maintained within a project.

Long Format Layer Names

In the long format, hyphens are used to separate the major group, minor group, and modifier to improve readability as shown in figure 5.1. While the AIA specification may seem highly detailed and exact, this degree of precision is needed to ensure standardization. It also allows individuals access to specific objects on a drawing. A complex drawing can easily have sev-eral hundred layers. The ability to quickly sort through these layers to display and plot spe-cific portions of the drawing is an important aspect of using a CAD system. The first space contains the major group specification. There are eight different major groups, as defined by the AIA. The eight major groups are shown in table 5.1.

Figure 5.1 The AIA long format layer groups.

A Architectural, Interiors, and Facilities ManagementS StructuralM MechanicalP PlumbingF Fire ProtectionE ElectricalC Civil Engineering and Site WorkL Landscape Architecture

Table 5.1 Eight major groups in the AIA naming format.

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While the major group areas correspond to the disciplines normally involved in architectural drawings, they are not designed to control or suggest which member of the design team should draw which objects. For example, the slab would be placed on the S-SLAB layer re-gardless of whether it was drawn by the structural engineer or architect.

Minor Groups. Minor groups are used to subdivide the major groups on the basis of infor-mation type or construction system. For example, the architectural major group (A) contains minor groups for furniture, roof, and ceiling information as well as for walls and doors.

Modifier. The modifier is added to a layer name to differentiate the minor group into catego-ries. For example, the doors (A-DOOR) layer can be further categorized as wood (A-DOOR-WOOD) or metal (A-DOOR-METAL).

User Defined Fields. The areas are designed to be open-ended, allowing additional layers to be added to accommodate special project needs. The user-defined field can be added after a modifier, or in place of a modifier. These fields can be up to 4 characters for long format character names.

Short Format Layer Names

The short format layer names consist of the major group, minor group, and modifier of the corresponding long format layer names. To create the short format layer names, combine the major group code, the first two characters of the minor group code, and the first two charac-ters of the modifier in the long format layer name. For example, the long format layer name A-DOOR-WOOD is converted to ADOWO in the short format. The short format layer names are composed as shown in figure 5.2.

Figure 5.2 The AIA short format layer groups.

The AIA layer naming format contains hundreds of modifiers that can be used when set-ting the layers needed for a drawing. The AIA publication CAD Layer Guidelines contains a detailed list of all the modifiers, as well as an excellent section describing how to determine what layers are needed for a specific project. The CAD Layer Guidelines publication can be obtained from the CAD Institute. They can be reached by calling their toll-free number 877-837-4100.

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Adding New Layers

You can add layers at any time with the Layer Control dialog box, accessed by entering layer at the Command: prompt, or by selecting the Layers button on the Object Properties toolbar.

Tutorial 5.1: Creating a Template with AIA Layers

For this tutorial, you will begin a new drawing and create layers for use in a D size architec-tural drawing. You will follow the AIA long format layer naming conventions.

1. Select the Open button from the Standard toolbar and load the DPROTO template draw-ing you created in Unit 4.

2. Choose the Layer Properties Manager button from the Layer toolbar.

The Layer Properties Manager dialog box appears.

3. Select the New Layer A-WALLbutton, enter A-WALL in the edit box, and press Enter. This layer is now added to the Layer Control dialog box.

Note that the first field contains an A, which is the major group architecture, interiors, and facilities management. The second field contains the minor group, WALL. This layer does not contain a modifier. Continue adding the following layers:

Layer Name Major Group Minor Group Modifier

A-CLNG Architecture Ceiling None

A-DOOR Architecture Doors None

A-FLOOR Architecture Floor None

A-GLAZ Architecture Windows None

A-PLFR-DIMS Architecture Floor Plan Dimensions

A-SHBD Architecture Title Block None

E-LITE Electrical Lighting None

E-POWER Electrical Power None

E-POWER-OTLT Electrical Power Outlet

E-POWER-SWCH Electrical Power Switch

P-FIXT Plumbing Fixtures None

S-FNDN Structural Foundation None

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4. After adding all of the layer names, your Layer Proeprties Manager dialog box should look like figure 5.3. Don’t close the drawing or dialog box; the next tutorial continues from here.

Figure 5.3 The Layer Properties Manager dialog box with the AIA layers displayed.

Changing the Layer Color

When a specific color is assigned to a layer, all objects drawn on that layer will display the assigned color. By assigning colors to different objects on the drawing, the drawing is much easier to read. If all dimensions are blue, for example, it becomes much easier to see the walls. If you are plotting to an output device that has color capabilities, you can also take advantage of the colors assigned to the layers and plot the drawing in color.

To change the colors of a specific layer, select the layer in the Layer Properties Manager dia-log box. The layer name becomes highlighted, and you can select the Set Color box on the right. Notice that you can also select more than one layer at a time if you want to assign the same color to several different layers.

Tutorial 5.2: Changing Layer Color

In this tutorial you will change layer colors for the layers you created in the previous tutorial. The AIA CAD Layer Guidelines publication leaves the selection of color up to the user. If you closed the dialog box after the previous tutorial, your layer names will be displayed in alpha-betical order.

1. The DPROTO drawing should appear on the screen, with the Layer Properties Manager dialog box displayed (figure 5.3).

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2. Select the color swatch beside the A-WALL layer.

The Select Color dialog box appears (see figure 5.4).

3. Choose the standard color Red. Notice that the word Red appears in the Color edit box. Continue changing the colors of the following layers. For layers that use a number in-

stead of a standard color, type the number in the Color text box in the Select Color dialog box.

Layer Name Color

A-CLNG White

A-DOOR 142

A-FLOOR 232

A-GLAZ Green

A-PLFR-DIMS Blue

A-SHBD White

E-LITE 203

E-POWER Magenta

E-POWER-OTLT 213

E-POWER-SWCH 221

P-FIXT Cyan S-FNDN White

Figure 5.4 Setting the layer color with the Select Color dialog box.

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Using Filters to Limit the Display of Layer Names

Some architectural drawings may contain hundreds of layer names. After you enter the names in the Layer Control dialog box, the names are automatically displayed in alphabeti-cal order when you close, then reopen the dialog box. To find a specific layer, you will have to scroll through all of the layer names to find a specific one you want to display or change.

The Layer Filter Properties dialog box allows you to change the way the layers are displayed. You can also set your own filter options (see figure 5.6). You can accesss the Layer Filter Properties dialog box by selecting the New Property Filter button in the

upper left of the Layer Properties dialog box or by pressing Alt+P while in the Layer Proper-ties Manager dialog box.

In the Layer Filter Properties dialog box, you can display layers that are on, off, frozen, thawed, locked, or unlocked (or any combination of these). In the Layer Filter Properties dialog box, you can use wild cards to specify layer names. This feature can be very handy if you follow the AIA standard for naming layers. For example, if you want to display only layers whose names pertain to the architecture, interiors, and facilities management (major group A), type A* in the Name edit box. Only layers whose names begin with A, and which refer to the architecture, interiors, and facilities management, appear in the list of layers. You can also use wild cards to display layers by Color or Linetype.

Figure 5.5 The alphabetized Layer Properties Manager dialog box with the AIA layers and colors displayed.

4. After changing all of the layer colors, your Layer and Linetype Properties dialog box should look like figure 5.5. Select OK to close the dialog box; the next tutorial continues from here.

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Tutorial 5.3: Filtering Layer Names

This tutorial continues from the previous tutorial. In this tutorial you will limit the display of layer names to the Electrical layers.

1. The DPROTO drawing should appear on the screen. Select the Layer Properties Man-ager button on the Layers toolbar to open the Layer Properties Manager dialog box.

The Layer Properties Manager dialog box appears with the layers you created in the previous tutorials.

2. Select the New Property Filter (Alt + P) button that appears in upper left of the Layer Properties Manager dialog box.

The Named Layer Filters dialog box appears, as shown in figure 5.6.

3. Enter Electric in the Filter name: text box. Enter E* in the Name text box. Your Layer Filter Properties dialog box should look like figure 5.6.

Figure 5.6 Enter E* to filter the layer names.

4. Select the OK button to add the flter name and close the Layer Filter Properties dialog box.

The Layer Properties Manager dialog box appears. Electric now appears as one of the layer filters. To apply a different filter simply select it in the menu on the left. After select-ing the Electric filter notice that only the Electrical layers appear as shown in figure 5.7. To turn off the filter and display all layer names, select All in the filters menu located on the left.

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Section 2: Understanding Linetypes

In the previous section you created layers following the AIA standard and assigned colors to them. Another important aspect of architectural drawings is the use of linetypes. The AIA CAD Layer Guidelines publication leaves the selection of linetypes to the user. The line conven-tions endorsed by the American National Standards Institute, ANSI Y14.2-M-1979 (R1987) are commonly used in many architectural drawings. This section discusses the creation of ANSI linetypes and how to apply them to your layers. In most cases, all elements on a se-lected layer will be displayed and plotted with the same color and linetype.

To use an ANSI linetype, it first must be created. While AutoCAD has a wide variety of line-types already created, including linetypes meeting the ISO standard, ANSI linetypes are not available. First you will create ANSI linetypes, then you will load them into the drawing. Lastly you will assign them to your template drawing.

What Are Linetypes?

A linetype is simply a repeating pattern of dots, dashes, and blank spaces. In manual drafting drawing a linetype can be a very tedious process, since you have to constantly measure and draw short dashes and spaces. Drawing with a CAD system makes this process much easier. When a linetype is defined in AutoCAD, the linetype name and its corresponding definition determine the specific sequence and relative lengths of dashes, dots, and blank spaces. When you use the linetype to create an object, AutoCAD automatically re-creates the specific sequence of dashes, dots, and blank spaces.

Most architectural drawings contain a variety of different linetypes. A certain type of line may be used on a drawing to represent a floor plan. Other lines may be used to represent electri-cal wiring or a foundation.

Figure 5.7 The Layer Properties Manager dialog box with the filter applied.

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Creating a Linetype

Creating a linetype is done at the Command: prompt by entering -linetype. Entering linetype at the Command: prompt displays the following prompt:

Command: -linetype

?/Create/Load/Set:

The options available at the linetype prompt are:

• ? This option is used to display all linetypes available in a selected linetype file. Re-sponding with a ? will access the Select Linetype File dialog box shown in figure 5.8. Linetype files will have a .lin extension. The AutoCAD default linetype file is acad.lin. After selecting the proper lin file, the AutoCAD Text Window will appear, showing all of the linetypes available in the selected file.

• Create The Create option is used to define a new linetype. This option will be explained fully in the next section.

• Load This will load a previously defined linetype. In order to load a linetype, it must exist in a lin file. The linetype can be a predefined linetype included with AutoCAD, or one previously defined with the Create command.

• Set After creating and loading a linetype, you can use Set to assign the linetype to the current object.

Figure 5.8 The Select Linetype File dialog box is used to load a lin file containing existing linetypes.

Tutorial 5.4: Creating ANSI Linetypes

While AutoCAD has many different linetypes available including those that meet the ISO stan-dard, linetypes that meet the ANSI standard need to be created. In this tutorial you will define ANSI linetypes in your DPROTO template drawing.

1. Your DPROTO drawing should be displayed.

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2. At the Command: prompt, enter -linetype and select the Create option.

Command: -linetype

?/Create/Load/Set: c

3. AutoCAD next asks you for the name of the linetype to create. Enter nhidden for a new hidden linetype.

Name of linetype to create: nhidden

4. In the Create or Append Linetype File dialog box, change to the proper drive and sub-directory and use ansi as the filename. You do not need to add the extension, since AutoCAD will automatically append the filename with lin.

5. Next AutoCAD prompts for a descriptive text. Use your dash and spacebar keys to create a pictorial representation of what the linetype will look like.

Descriptive text: - - - - - - - - - -

6. Next you will enter the pattern, following the ANSI guidelines. Enter pattern (on next line):

A,0.125,-.04

This defines a new hidden line segment with a dash of 0.125 units and a space of .04 units.

7. Although the electrical linetype we are creating is not an ANSI standard linetype, we are creating it specifically to show electrical wiring in our drawings. Note that it is a slight modification of the Nhidden linetype. Create a center and electrical linetype, using the fol-lowing parameters:

Name Storage File Descriptive Text Pattern

Nelect ANSI __ __ __ __ __ __ .250,-.04

Ncenter ANSI ______ __ _____ .5,-.0625,.125,-.0625

8. After defining all three linetypes, press Enter at the ?/Create/Load/Set: prompt to return to the Command: prompt.

Loading and Setting a Linetype

After creating a linetype, it must be loaded before it can be assigned to a layer. Both of these tasks can be done in the Layer Properties Manager dialog box. To assign a linetype to a layer, first select the applicable layers. Next select Continuous in the Linetype column across from any of the selected layers. When the Select Linetype dialog box appears, select the Load button to access the Load or Reload Linetypes dialog box. Change to the proper drive and directory that contains the lin file of the linetypes you want to load. By default, the stan-dard AutoCAD linetypes are located in the acad.lin file.

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After loading the necessary linetypes, select the linetype you want to assign to the layer and click OK. Linetypes are assigned to a given layer so that all objects drawn on that layer will have that linetype automatically. Linetypes are set to a layer for the same reasons that colors are.

Tutorial 5.5: Loading and Setting ANSI Linetypes

In the previous tutorial you created three different ANSI linetypes for use in an architectural drawing. After creating a linetype, it must be loaded and assigned to a layer. In this tutorial you will load and assign the three linetypes you created to the DPROTO drawing.

1. Make sure that the DPROTO drawing is displayed and you defined three linetypes as described in the previous tutorials.

2. Select the Layer Control button on the Object Properties toolbar to access the Layer Properties Manager dialog box.

The Layer Properties Manager dialog box appears. If the filter is still applied to the layers, select All in the menu on the left.

3. Select the E-POWER layer and choose the word Continuous in the Linetype column.

The Select Linetype dialog box appears.

4. Select the Load button to access the Load or Reload Linetypes dialog box.

5. Select the File button in the Load or Reload Linetypes dialog box. Change to the proper drive and directory and load the ansi.lin file you created in the previous tutorial. This file contains the linetype definitions of your ANSI linteypes.

Figure 5.9 The Select Linetype dialog box with the ANSI linetype definitions.

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Figure 5.10 The Layer Properties Manager dialog box with the ANSI linetype definitions and colors applied to the layers.

6. Highlight all of the ANSI linetypes, then select OK.

You are returned to the Select Linetype dialog box shown in Figure 5.9 with the ANSI linetypes now displayed.

After loading the linetypes, the next step is to assign them to the necessary layers.

1. In the Layer Properties Manager dialog box select the word CONTINUOUS in the same line as the E-POWER layer. When the Select Linetype dialog box appears select the Nelect linetype. Select OK to close the dialog box.

You are returned to the Layer Properties Manager dialog box, with the Nelect layer as-signed to the E-POWER layer.

2. Assign the Nhidden linetype to the S-FNDN layer, and the Ncenter linetype to the A-FLOOR layer. Note that you do not have to reload the linetypes each time. Since you already loaded them, they will appear in the Select Linetype dialog box.

3. Your Layer Properties Manager dialog box should look like figure 5.10, with the proper colors and linetypes assigned to the layers.

4. Select OK to close the Layer Properties Manager dialog box, then select the Save button on the Standard toolbar to save the DPROTO template drawing

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Understanding Linetype Scale (LTSCALE)

When you created the ANSI linetypes, they were defined by a series of dashes and spaces. The LTSCALE command is used to change the relative scale of the dashes and spaces that define a linetype. As long as the LTSCALE is set to 1.0 (the default), the length of the dashes and spaces you defined for the linetypes will remain the same size.

Most architectural drawings are created full-size on AutoCAD. When the drawing is plotted, it remains full-size while the plot is scaled. If the drawing is going to be plotted at full scale (1=1), the default linetype scale is fine. If the drawing is going to be plotted at a different scale, you need to change the size of the linetype by increasing the value of the linetype scale (to 48, for example, if the plot scale is 1/4”=1’). You can change the linetype scale by selecting Options/Linetype/Global scale, or by entering linetype at the Command: prompt.

Using either method will set the linetype scale for all linetypes in the entire drawing. After you set a new linetype scale factor, AutoCAD automatically regenerates the drawing unless you have the automatic regen turned off.

Unit ReviewProper use of layers not only helps organize your drawing’s linetypes, colors, and objects, but also helps in visualization and plotting. Standardizing layers and linetypes is a very important part of CAD work. Without standards to follow, a simple drawing can become very confusing and difficult to use.

Fortunately, standards exist that aid in the standardization of architectural CAD drawings. The American Institute of Architects (AIA) , in their publication CAD Layer Guidelines, recom-mends layer naming and conventions for architectural drawings.

The AIA leaves the selection of color and linetype to users. Most architectural drawings use the ANSI linetypes, although this is not a requirement. If you want to use ANSI linetypes in your drawing, you will need to create them since AutoCAD by default does not contain ANSI linetypes.

Although most architectural drawings done on AutoCAD are drawn full-size, when the draw-ing is plotted, the plot is scaled to enable the drawing to fit on a standard size of paper. The LTSCALE command is used to achieve the correct linetype scale in the finished drawing. In most cases the linetype scale should be set to the working scale of the drawing.