Category Archives: Guidelines for Using Building Information Modelling

Guidelines for Using Building Information Modelling – Technical Requirements Spatial Location and Co-ordination

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5.1.1  Spatial Location and Co-ordination

The BIM origin point and orientation of the model should be based on the actual location of the development by referring two widely used Hong Kong geodetic horizontal and vertical control networks, namely the Hong Kong 1980 Grid System (HK 1980 Grid) and Hong Kong Principal Datum (HKPD).

The HK 1980 Grid and HKPD should be presented in metres corrected to three decimal places (i.e. (8XX,XXX.XXX mN, 8XX,XXX.XXX mE) and (X.XXX mPD). Negative sign should be added for negative mPD (i.e. – X.XXX mPD).

Guidelines for Using Building Information Modelling – Technical Requirements Mathematical Modelling

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5.1.1  Mathematical Modelling

All dimensions should be true dimensions generated automatically by the software. Numerical dimensions inputted manually in the BIM file are not acceptable.

Guidelines for Using Building Information Modelling – Technical Requirements Unit and Measurement

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  • Unit and Measurement

The model should use consistent unit and measurement across the project with default drawing units in millimetres (mm) with a precision rounded up to the nearest mm unit.

All floor areas and volumes should be presented in square metres (m2) and cubic metres (m3) respectively and rounded off to three decimal places.

All site areas should be rounded off to the nearest 0.1m2 for site area less than 2,000m2 and to the nearest 1m2 for site area of 2,000m2 or above in accordance with PNAP ADM-21.

Guidelines for Using Building Information Modelling – Specification for Native File

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1.  Specification for Native File

The native file should contain the building proposal model and complete with all views, schedules, calculations and annotations essential for the production of the prescribed plans. All BIM submissions should adopt a unified modelling methodology, and the native file should be created in a standardised file structure.

Guidelines for Using Building Information Modelling – Level of Development

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4.1          Level of Development

BIM technology enables the BIM model to contain geometrical and non- geometrical information as BIM elements. Geometrical information includes size, volume, location, orientation, etc. while non-geometrical information includes specifications, performance data, cost, etc.

BD notices various international organisations attempting to standardise BIM elements. One of the popular standards is the “Level of Development” (LOD), according to the American Institute of Architect. The LOD is classified into six categories namely LOD 100, LOD 200, LOD 300, LOD 350, LOD 400 and LOD

500. Reference on the LOD classification and specification may refer to https://bimforum.org/ . As a general principle, APs are advised to adopt LOD 300 in the preparation of BIM files though on some occasions APs may adopt LOD below 300 (e.g. indication of E/M plants, exhausted ducts) or LOD above 300 (e.g. special design details).

Guidelines for Using Building Information Modelling – Administrative Requirements

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4.1          Administrative Requirements

  • The BIM files should be stored in a non-rewritable DVD-ROM in ISO/IEC 13346:1995 format (i.e. DVD format). Except otherwise agreed by the BA, all other electronic submission media are not acceptable.
    • Each BIM file should be limited to the size of 500MB. Each BIM  file should contain 3D model, views, schedules, as well as the pre-set drawing sheets including plans, area diagrams, calculations, etc. for the production of the hardcopy of prescribed plans. The text file should be included in the DVD-ROM to describe the linked files’ hierarchy structure.
    • BA currently accepts BIM native files created by (i) Revit version 2017 or later and (ii) ArchiCAD version 21 or later only. As BIM technology is fast developing, there may be add-ons assistant programs or in-house scripts used for enhancing automation in the BIM file production. Add-ons or other implanted automation may cause the submitted BIM file not  usable by BD’s standard Revit or ArchiCAD software. It is the APs’ responsibility to ensure that the purposes of the BIM model are served, as elaborated in the Guidelines, without relying on add-ons or additional scripts.
    • The use of software, other than Revit and ArchiCAD, requires prior acceptance from the BA. As a general rule for such prior acceptance, the APs should submit at least one test sample together with the enabling software to the BA for installation and testing. For the avoidance of doubt, BA does not accept any web based BIM software.
    • Revit files should be saved in “.rvt” format and ArchiCAD files in “.pla” format only. All other lightweight, compressed or zipped file  formats such as “.dwf”, “.dwfx” and “.bimx” will not be accepted.
    • Drawing title blocks with drawing number, revision number, legends, site

/ project title, drawing title, etc. as detailed in Section 5.4.1 should be inserted in every drawing for identification purpose.

  • BIM files submitted in DVD ROM format should be self-contained and detached from the originating server. It shall be able to  be  opened on any standalone computer with the abovementioned software. All “X-Ref” files for the BIM model such as xlsx and pdf files should be stored in respective sub-folders in DVD ROM, and the link between all “X-Ref” files and BIM main file should be appropriately connected.

Guidelines for Using Building Information Modelling – BIM File Submission Requirements

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1.  BIM File Submission Requirements

  • 4.1          Introduction

This chapter describes the requirements on BIM GBP electronic files (BIM files) accompanying the submission of the prescribed GBP plans to the BA for the purposes of PNAP ADM-19.

4.2          Performance Requirements

  • All BIM files shall meet the following requirements:
    • BO and all allied regulations;
    • Relevant codes of practice, PNAPs and circular letters issued by the BA; and
    • Relevant BIM sample templates (Revit or ArchiCAD) prepared by the BA.
    • Information contained in BIM files shall be identical to the information shown on the prescribed GBP plans. Prescribed plans submitted to the BA should be directly generated from the corresponding BIM model.
    • The Colour Code System as specified in Section 5.1.4 of the Guidelines for various building components and area diagrams shall be adopted.
    • Area diagrams should be shown with the corresponding halftone under laying floor plans for ease of verification.
    • All linear dimensions and area diagrams of the BIM file should be fit for verification to the extent that the accuracy of area calculations can be checked and mathematical errors, if any, can be identified.
    • The computation of all area diagrams on prescribed plans should be verifiable with the BIM software, both by selecting a pre-set zone / area and by specifying points to define what to measure.
    • All irrelevant data for statutory submission, such as lighting, reflected ceiling plan, building services provisions and the like shall be removed from the BIM file.

Guidelines for Using Building Information Modelling – Scope

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The Guidelines cover the following:

  • BIM file submission requirements
    • Specification for native file
      • Technical requirements
      • Essential views for composing the prescribed plans
      • Essential schedules for composing the prescribed plans
      • Amendment Plans and Alterations & Additions Plans
      • Other essential information on prescribed plans or BIM files for BD
      • Other information on prescribed plans or BIM files for other departments
    • File structure and file naming convention

Guidelines for Using Building Information Modelling – Objectives

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1.  Objectives

The Guidelines aim to set out:

  • General guidelines to facilitate APs in preparing GBP by BIM authoring software; and
    • Recommended good practices for the enhancement of submission standard.

While non-conformity with the Guidelines will not constitute a ground for disapproval of the plans, the Building Authority (BA) may not accept the BIM GBP electronic files for the mathematical calculation of areas depending on the degree of non-conformity.

Guidelines for Using Building Information Modelling – Background

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Building Information Modelling (BIM) technology is identified as one of the key drivers to enhance the design, construction and project management in the construction industry. Buildings Department (BD) encourages Authorized Persons (APs), Registered Structural Engineers (RSEs) and Registered Geotechnical Engineers (RGEs) to consider adopting BIM in their building projects.

BD accepts the use of computer for calculating floor areas of buildings in the preparation of general building plans (GBP) submission. Practice Note for Authorized Persons, Registered Structural Engineers and Registered Geotechnical Engineers (PNAP) ADM-19 sets out the rules and pre-requisites regarding such computer use. If BIM technology is used in the preparation of GBP, this  Guidelines for Using Building Information Modelling in General Building Plans submission (the Guidelines) should be followed.