CAD Standards September 2010personal.rhul.ac.uk/ukyb/044/Car Park 14 - Tender Pack/APPENDICES... · 2 CAD Drafting Standards 2.1 Overview CAD This section relates to traditional CAD

© 2010 Excitech Ltd Page 1 of 27

CAD Standards

September 2010

For

ROYAL HOLLOWAY

UNIVERSITY OF LONDON


Prepared by

Excitech Ltd Design Technology Centre 8 Kinetic Crescent Innova Business Park Enfield EN3 7XH (t) 0845 370 1500 (f) 0845 380 1400 (e) [email protected] (w) www.excitech.co.uk

Author: John Williams

Checked: D Bezants, Leigh Atkinson

Approved:


Contents

Contents ................................................................................................................................................ 2

1 Introduction..................................................................................................................................... 6

1.1 Document Purpose ................................................................................................................. 6

1.1 Scope ...................................................................................................................................... 6

1.2 Responsibilities ....................................................................................................................... 6

1.2 Document Audience................................................................................................................ 6

2 CAD Drafting Standards................................................................................................................. 7

2.1 Overview ................................................................................................................................. 7

2.2 File Naming ............................................................................................................................. 8

2.3 Spatial Co-ordination .............................................................................................................. 9

2.4 Origin and Orientation............................................................................................................. 9

2.5 External File Referencing...................................................................................................... 10

2.5.1 External Reference File Paths ....................................................................................... 11 2.5.2 Insertion points and origins............................................................................................ 11

2.6 Working Units........................................................................................................................ 11

2.7 Templates ............................................................................................................................. 12

2.8 Layers ................................................................................................................................... 13

2.9 Layer Definition ..................................................................................................................... 14

2.9.1 Mechanical .................................................................................................................... 16 2.9.2 Electrical ....................................................................................................................... 16 2.9.3 Architectural ................................................................................................................... 16 2.9.4 Public Health.................................................................................................................. 17 2.9.5 Fire................................................................................................................................. 17 2.9.6 Security .......................................................................................................................... 17 2.9.7 Gas ................................................................................................................................ 18 2.9.8 Topology ........................................................................................................................ 18 2.9.9 Annotation...................................................................................................................... 19 2.9.10 Ventilation ...................................................................................................................... 19 2.9.11 Location/Position ........................................................................................................... 19

2.10 Symbols ................................................................................................................................ 20

2.11 Line Definition ....................................................................................................................... 21

2.11.1 Line Widths .................................................................................................................... 21 2.11.2 Colour Plots ................................................................................................................... 21

2.12 Linetypes............................................................................................................................... 22

2.12.1 Ltscale............................................................................................................................ 22 2.13 Style ...................................................................................................................................... 23


2.14 Dimensions ........................................................................................................................... 23

2.15 Text and Scale ...................................................................................................................... 24

2.15.1 Text ................................................................................................................................ 24 2.15.2 Scale .............................................................................................................................. 24


2.16 Paper Space ......................................................................................................................... 25

2.16.1 Layouts .......................................................................................................................... 25 2.16.2 Dimensioning ................................................................................................................. 25 2.16.3 Viewports ....................................................................................................................... 25

2.17 Drawing Handover ................................................................................................................ 26

2.18 Statement of Compliance...................................................................................................... 26

3 RHUL CAD Standard Statement of Compliance.......................................................................... 27


1 Introduction

1.1 Document Purpose

This document details the Estate Services Computer Aided Design (CAD) Standards which users of RHUL CAD systems and external contractors are required to follow and sets out to describe the general management and creation of drawings as part of both major and minor projects. The use of this Standard will ensure a consistent approach and easier exchange of CAD data within RHUL and with contractors.

1.2 Scope

The department has responsibility for the management of drawing related information produced as part of major or minor projects related works

1.3 Responsibilities

The Head of Projects is responsible for implementation and monitoring the requirements of the following procedure.

1.4 Document Audience

a) Royal Holloway b) Excitech Ltd.


2 CAD Drafting Standards

2.1 Overview

CAD This section relates to traditional CAD Standards procedures and gives a detailed definition of the standard and methods to be used for CAD drafting production. This section sets out the underlying principles and procedures that must be used when preparing CAD drawings and models for RHUL. All drawings must be created in AutoCAD software or alternatively be supplied in an AutoCAD .DWG format that retains the AutoCAD structure. Where a non-AutoCAD drafting system has been used to originate the data, the contractor must ensure that the data can be used as per an AutoCAD created file and have suffered no loss of integrity or accuracy from any conversion processes. A sample of all CAD data must be validated and agreed by RHUL. DXF and Scan formats are only acceptable by prior agreement with RHUL. Whichever way the CAD files are created, they need to conform to the CAD Standards laid out in the following sections of this document.


2.2 File Naming

File names should be unique, and follow the convention laid out below. RHUL will issue blocks of numbers to contactors for use on specific projects. Any unused numbers must be discarded and new drawing numbers generated for new projects. The RHUL internal filename structure consists of 3 elements each separated by a dash “-“ symbol. The different elements are broken down as follows:

BUILDING NAME

LEVEL REVISION

FOUNDERS 1 A BUILDING NAME – The Building Name.

LEVEL – The floor level

. DRAWING NUMBER – A 4 digit numeric code. This is a sequential number starting from

0001.

REVISION – A single digit alpha code. This describes the revised state of the drawing. The initial issue will be A rising through to Z. A revision will be raised when single or multiple changes are made to a drawing previously issued as part of the tender or construction process, on its reissue to the tender or construction process. Filename example: FOUNDERS/1/0001/A


2.3 Spatial Co-ordination

CAD modelling systems assemble the model information needed to generate production drawings, based on Cartesian coordinates for all relevant points needed to define the project. The following sections describe the requirements of the fully coordinated system which are applicable to either a 2D or 3D design project. In Figure 4 the points 1, 2, 3 and 4 can each be precisely located in space by three coordinates, which are given in relation to three planes at right angles. The point of intersection of the three reference planes is called the ‘origin’ of the coordinate system (at coordinate reference 0,0,0). The coordinates are commonly referred to as ‘world coordinates’ and the space defined by their positive values is known as ‘model’ space. Spatial co-ordination is an essential requirement of good quality production information and a disciplined approach to managing coordinate systems across all data files is essential.

2.4 Origin and Orientation

Based on the guidelines in the preceding section a specification of a Building Origin and Building Grid must be defined for each main building within each RHUL project prior to any design work being carried out. The building grid definition must relate to a transformation from a Project Grid and be fully documented. Similarly, a Project Origin and Project Grid must be defined for each RHULproject prior to any design work being carried out. The project origin and grid definition must relate to a site survey and/or OS coordinate grid and be fully documented. The vertical (Z) coordinate must be included in any origin and grid definitions.

IMPORTANT: Potential accuracy issues with large x/y coordinate values when working in millimetres on a project must be taken into account and minimised. This can be done by ensuring that the (World UCS) origin in model files is defined in close proximity to the project data and by careful management of the building origin and grid within a project.

X1, Y1, Z1

X2, Y1, Z2 X1, Y1, Z2

X2, Y1, Z1

X plane

Z p

lane

Y plane

1 2

3 4

0, 0, 0


2.5 External File Referencing

The use of external reference file “nesting” is to be avoided as a general principle.

When working in the model file environment, the OVERLAY option should be used when attaching reference files to avoid “nesting”. Overlaying Models with Models as the standard procedure will prevent uncontrolled nesting and ensure that unwanted information is not unintentionally referenced into files.

Although the standard method of attaching external references to model files should be using the OVERLAY option, there are rare occasions where using the external reference ATTACH option may be appropriate. These include the use of repeated elements of the design (e.g. a toilet layout) which do not have a unique location in the project. The ATTACH option should be employed by default when referencing model files into sheet files for the purposes of producing a drawing sheet that will eventually be published as hardcopy production information.

A B A B

AT

TA

CH

OVERLAY

OVERLAY

A BSHEETS

MODELS

AT

TA

CH

AutoCAD external reference attach options


2.5.1 External Reference File Paths

This normally only becomes an issue when files containing other referenced files are issued outside of a company network. Attempting to replicate one company’s filing structure or enforcing a standard filing structure on all other companies in a project is not an option. The use of the AutoCAD “etransmit” function assists as it places all files in one place irrespective of their original location. If references cannot be found in a path that no longer exists – AutoCAD will search in the location of the current drawing file for its associated references. It is highly recommended that a “relative path” convention is used for attaching all external reference files.

2.5.2 Insertion points and origins

All referencing and insertion operations with respect to model files shall be carried out when in World UCS. The absolute xyz coordinate system within all model files within a project must relate to a defined building grid origin and orientation. Note that this is not the standard convention within the ADT and ABS Project Navigator where data for different floor levels is all created at a zero z elevation.

2.6 Working Units

With regard to working units the following will be applicable

Metric units must be used throughout.

Building layouts, sections, elevations and details shall be drawn in millimetres as the drafting unit with the AutoCAD units set to decimal and dimensions in millimetres. (Insertion Units to be set to millimetres.)

Site surveys, Site layouts and Site-wide external works and services shall be drawn in

metres as the drafting unit with the AutoCAD units set to decimal and dimensions in millimetres. (Insertion Units to be set to metres.) Millemetres may be used for site related modelling if required as long as this does not introduce a risk of the accuracy issues noted below.

IMPORTANT: Potential accuracy issues with large x/y coordinate values when working in millimetres on a project must be taken into account and minimised. This can be done by ensuring that the (World UCS) origin in model files is defined in close proximity to the project data and by careful management of the building origin and grid within a project.


2.7 Templates

To ensure continuity of format and layout, standard RHUL templates should be used. The templates (A0 – A3) are available from the RHUL CAD Symbol Library and have provision for contractor’s information. The benefits of this requirement are as follows: -

A standard format and layout used throughout all projects All contracting groups, from main contractor to sub-contractor, to use the same drawing

borders Standardisation of drawing window that will permit ease of information transfer within

RHUL and with external groups

Inclusion of key attributes within the title block for ease of transfer to RHUL's drawing register, when importing drawing files.


2.8 Layers

It is important that everyone involved in generating or using CAD data has a good understanding of the reasons for a disciplined layer naming convention. Typical uses for Layer classifications include – - Graphical representation Layers have traditionally been used in a 2D CAD drafting environment to control graphical representations (e.g. colour, linetype, lineweight). It is common practice to create CAD drawing objects where the default property for these representations is “BYLAYER”, so that they inherit the graphical properties assigned to the layer that they are on. This provides a convenient method for managing drawing information and controlling the appearance of the published drawings. - Visibility of data in different contexts The ability to turn the visibility on or off (freeze/thaw) for all objects on a given layer or set of layers has benefits not only while the data is being created and updated but also when the data is being published. - Ownership Within the concept of a Common Data Environment strategy there is only a single representation of any object within the CAD project database. Where an object needs to be referenced by multiple users and disciplines it is important that the “owner” of that object is the only one who can modify it. Layer classification provides one method of specifying ownership (typically via a “Discipline” field within the layer name). However a more appropriate method, particularly within a 3D CDE environment, is to specify ownership at a document level. - Locking Related to the concept of ownership, layers can also be “locked” (i.e. objects on a locked layer cannot be modified). This facility allows users to temporarily prevent accidental modification of objects.


2.9 Layer Definition

A consistent set of layer naming standards must be applied to all 2D and 3D CAD models and sheet files developed.

The use of ”layers” is a standard method of classifying CAD data. In AutoCAD applications, data objects (whether representing annotation or real world objects within the project) each exist on a specified layer. A basic RHUL layering convention has been established to cover most types of work undertaken. The layer then has a descriptive name to allow for easy recognition. The last part of the layer is made up of an optional 2 character code which best represents its position / location. Example layer name:

Natural Gas-BG

Natural gas – Below ground


On large drawings / projects there may be a need to create additional layers. The user may determine these, as long as they are suffixed by the standard alphanumeric characters. Additional layer names created should be used consistently throughout a project. The standard layer convention does not determine the allocation of screen colours to any particular layer and these should be determined in accordance with the Line Definition. It is acknowledged also that there are some existing construction industry layering conventions, such as BS1192 Part 5 and ISO 13567 etc. If these standards are used then they should be converted into the RHUL layer standard prior to transmittal of drawing data. Protocol checks will be carried out automatically once RHUL have received such data to verify conformity to the RHUL Layering standard. Protocol checking software can be obtained from RHUL. This software can be used to check a drawing for conformity to the RHUL standard before transmittal, therefore minimising on drawings being returned. The next set of 10 tables list the descriptive codes covering the most commonly used layers created when producing drawings:


2.9.1 Mechanical

2.9.2 Electrical

2.9.3 Architectural

CODE DEFINITION Acid & Alkali Acid / Alkali Chilled water Chilled water Compressed air Compressed air Condense Condense Cold water down service Cold water down service Cold water main Cold water main Dry riser Dry riser High temp hot water High temp hot water Hot water service Hot water service Hydraulics Hydraulics Low pressure hot water Low pressure hot water Medium temp hot water Medium temp hot water Oil Oil Refrigeration Refrigeration Steam Steam

CODE DEFINITION Conduit Conduit High voltage cable High voltage cable Lighting Lighting Low voltage Low voltage Cable tray Cable tray Trunking Trunking

CODE DEFINITION Block work Block work Brick work Brick work Ceiling Ceiling Concrete Concrete Door Door Furniture Furniture Partition Partition Staircase Staircase Structural features Structural features Window Window


2.9.4 Public Health

2.9.5 Fire

2.9.6 Security

CODE DEFINITION Foul water drainage Foul water drainage Surface drainage Surface drainage

CODE DEFINITION Fire extinguisher water Fire extinguisher water Fittings Fittings Fire extinguisher foam Fire extinguisher foam Fire System Fire System

CODE DEFINITION Security Alarm Security Alarm Public Address Public address


2.9.7 Gas

2.9.8 Topology

CODE DEFINITION Acetylene Acetylene Air Air Compressed Air Compressed Air Helium Helium Hydrogen Hydrogen Low Pressure Gas Low Pressure Gas Natural Gas Natural Gas Nitrogen Nitrogen Oxygen Oxygen

CODE DEFINITION Tree boles Tree boles Bottom of a bank Bottom of a bank Change of surface Change of surface Dropped kerbs Dropped kerbs Fences Fences Foliage Foliage Survey gridlines Survey gridlines Gulleys Gulleys Inspection covers Inspection covers Kerbs Kerbs Street furniture Street furniture Top of a bank Top of a bank Tree canopies Tree canopies


2.9.9 Annotation

2.9.10 Ventilation

2.9.11 Location/Position

The table below shows the optional last 2 characters in the layer name which denote the object’s position / location:

The position of services is further indicated by the use of non continuous line types.

CODE DEFINITION Dimensions Dimensions TEXT25 Text 2.5 mm high TEXT35 Text 3.5 mm high TEXT5 Text 5 mm high TEXTV Text other height Drawing border Drawing border

CODE DEFINITION Extract Extract Supply Supply WC WC

CODE DEFINITION HL High level LL Low level IV In a void BG Below ground


2.10 Symbols

All symbols should conform where possible to the relevant BS or ISO standards. The main standards relevant to disciplines likely to be used on RHUL projects are: Mechanical (pipework) and HVAC -BS 1553 General Engineering Electrical -BS EN 60617 Fire Engineering -BS 9999 Security/Alarms -BS 4737 (part 5.2)

Any symbols which are generated outside of these standards, should be identified on a legend sheet, or alternatively, in the area above the title block on a drawing. Where AutoCAD Blocks are created of these symbols, they should be saved with millimetres as the insertion unit value and should have a descriptive name. Where applicable an adequate description of the symbol must be included within the AutoCAD dialog when creating the block.


2.11 Line Definition

2.11.1 Line Widths

Line widths, as they appear in finished plots, are traditionally determined by assigning different on screen colours to distinguish thickness of line. Conventional design office practice demands that most drawing work is plotted in mono for ease of copying and that differing pen widths are used to emphasise detail. Pen plotters have a limited range of pen widths available, whereas users of raster devices, such as inkjet plotters have access to a far wider range. The table below shows 5 of the AutoCAD standard colours being applied to the RHUL standard pen widths. Screen colours for pen widths.

.18mm .25mm .35mm .50mm 1 mm RED GREEN YELLOW CYAN BLUE

A standard RHUL.CTB (Plot settings file) can be supplied for use with plotting for AutoCAD 2000 and above.

2.11.2 Colour Plots

With the increase in colour inkjet technology, colours are often used on plots for presentation work. In these cases, the assignment of screen colour and pen widths must be individually set for the drawing.


2.12 Linetypes

For general guidance, the following linetypes are to be used for specific types of lines. CONTINUOUS - Low Level / General CENTRE2 - High level HIDDEN2 - Below ground PHANTOM2 - In a void Other Linetypes are permitted but must be accompanied by either a legend sheet or a key / legend within the drawing itself.

2.12.1 Ltscale

Ltscale is a variable inside AutoCAD which controls the spacing of the dashes and dots of a broken linetype. This needs to be kept to a standard setting to maintain uniformity of appearance between drawings.


2.13 Style

To keep the continuity between drawings the dimension style RHULDIM should be used. This style consists of closed filled arrow heads and is associated with the ROMANS text style. Text height for the dimension should be 2.5 mm high and this is set within the style. All text on dimensions is coloured yellow so as to plot at a 0.35 mm line weight.

2.14 Dimensions

Many of the problems that arise on construction sites can be traced to errors and ambiguities in the dimensions. Such errors occur when information is entered incorrectly, or dimensions are added as text that is unrelated to the underlying coordinate system. The use of incorrect dimensional information will prevent effective spatial coordination. All models will be created at a scale of 1:1 using real world coordinates and drawings will be based on the model information. Drawing models should all be constructed with component parts drawn accurately at nominal size or mid tolerance; this is essential in order to maintain model integrity. The concept of 'not to scale' within models will not be permitted. All dimensions must be generated as associative dimensions and never added as text; this is because text has no relationship to the underlying CAD coordinates and will cause the relative positions of elements in a drawing to be compromised. Dimension text must not be modified and automatic or associative dimensions should never be broken into their constituent parts. All dimensions should be placed on the N-DIMS layer.


2.15 Text and Scale

To maintain consistency between drawings it is advisable to work to a standard drawing style throughout a project. This is particularly so where BLOCKS or XREF’s are being used. BLOCKS and XREF’s must be inserted on layers that will not be frozen inadvertently.

2.15.1 Text

The standard AutoCAD font, ARIAL should be used in most cases. It is recommended that for dimensions and general notes the text height should be 2.5 mm, for sub-headings 3.5 mm and for main headings 5mm, all using a .35 mm (Yellow) or .25 mm (Green) line thickness.

2.15.2 Scale

All scale drawings must be created at 1:1 (Full Size). Where Paper Space is being used, the model should still be at 1:1. AutoCAD drawings will normally be created with one AutoCAD UNIT equalling one millimetre. When scale drawings are being created, the text heights and other variables such as Ltscale and Dimscale need to be altered to suit, if ModelSpace is being used. If a RHUL drawing border is inserted into a new drawing layout using the RHUL CAD Symbol Library, these variables will be set automatically, as shown in the following table. If all annotation is carried out in PaperSpace, then these variables will be catered for automatically.

Dwg Scale Ltscale Dimscale 2.5mm

Text

3.5mm

Text

5mm Text

1:1 1 1 2.5 3.5 5

1:50 50 50 125 175 250

1:100 100 100 250 350 500 1:50 is the preferred scale for most drawings, with 1:100 the second choice, but there will be drawings such as site plans, where other scales are more appropriate.


2.16 Paper Space

Paper space is to be used whenever possible.

2.16.1 Layouts

Layouts should be populated by the RHUL borders using the customised toolbars. This will ensure scales and text heights etc. are maintained.

2.16.2 Dimensioning

All annotation and dimensioning, where possible, is to be created in paper space using fully associative dimensions. Utilising this option will also help in productivity and unifying dimension scales across viewports.

2.16.3 Viewports

Viewports can be created and their contents scaled using the Viewport toolbar. If different scales are used within one layout then those scales should be clearly marked adjacent to the viewports.


2.17 Drawing Handover

All CAD files should be transferred to RHUL in either of the following formats: -

Electronic Transfer (e-mail). - For low volume transfer only. CD ROM, DVD or Flash Drive. - For high volume transfer.

A register of electronic file content must be provided with each issue and at the completion of a

project a database of project information must be provided, which conforms with the drawing and document management system used by RHUL.

2.18 Statement of Compliance

To ensure compliance with the Standard, contractors are shall complete and return the Statement of Compliance, a sample of which can be found in Section 3. Failure to do so may deem the tender submissions to be invalid. Main contractors must ensure that any sub-contractors supplying drawings also comply with this Standard.


3 RHUL CAD Standard Statement of Compliance

Completion of this form is required as confirmation of the contractor having read, understood and accepted the requirements of RHUL CAD Standards document. If this form is not completed and returned, as requested, any tender submissions may be deemed invalid. The contractor awarded the contract will be expected to provide a CAD Method Statement within 2 weeks of being awarded the contract. The main contractor must be responsible for ensuring that any sub-contractors supplying drawings comply with these standards.

Details of CAD System:

CAD software and versions Add on/ancillary software Work station types and no off Operating system Plotting facilities Back-up facilities and frequency Protection of Data (ie storage

methods) Method of data transfer to RHUL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Additional comments or information: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .

RHUL Project Reference

.................... ...................

Signed: ..............................................

Name: ....................... Position:

..... . . . . . . . . . . . . Date: ................................................

Company/Site:

........................ ..................... Tel No: ..............................................

NB: COPY OF COMPLETED FORM TO BE RETURNED TO RHUL.

RHUL Completed form seen and accepted by RHUL Representatives: INTERNAL Project Manager

.................... ............... Date: ...................... ................

USE ONLY CAD Manager .................... ..................

Date: ...................... ................

Documents

CAD Standards September 2010personal.rhul.ac.uk/ukyb/044/Car Park 14 - Tender Pack/APPENDICES... · 2 CAD Drafting Standards 2.1 Overview CAD This section relates to traditional CAD