Introduction

Underground drainage networks and cable ducts are essential components of virtually every civil engineering and building project in Hong Kong, yet quantity take-off for these services remains largely a manual exercise. While BIM-based quantity take-off software is widely available for superstructure elements, no commercially available solution measures underground drainage or cable duct networks in accordance with the applicable standard methods of measurement. Quantity surveyors must therefore interpret model geometry by hand — in particular the depth of pipe invert below the corresponding ground surface, which governs excavation itemisation. The process is time-consuming, difficult to audit, and inconsistent between practitioners, and it prevents the industry from realising the value of the information already embedded in its BIM models.

This project develops open, freely available software plug-ins that generate Bills of Quantities directly from information-rich BIM models of drainage and cable duct networks, in compliance with the Standard Method of Measurement for both civil engineering and building works. By automating the interpretation of model data into measurable items, the research closes a long-standing gap between design modelling and cost estimation for underground services.

Project Description

Scope. The research covers drainage pipes and manholes, and cables and ducts, across both civil engineering works and building works, implemented for Autodesk Civil 3D 2024 and Autodesk Revit 2024.

Standards studied. The team carried out a detailed study of the relevant measurement standards — Section 5 of the SMM for Civil Engineering Works, SMM5 for Building Works, and the ASD Model Bill — alongside the governing BIM standards: the CIC BIM Standards (General), the CIC BIM Standards for Underground Utilities, the DSD BIM Modelling Manual, the HKIS Measurement Information Requirements, and the ASD-BIM Guide for Cost Estimation. Interviews with civil and building works stakeholders informed the practical requirements.

Modelling methods. Consistent modelling conventions were defined so that models carry the data measurement requires. Drainage is modelled as a Pipe Network in Civil 3D and as pipework in Revit, with DSD manhole families defined for both platforms. Cable ducts are modelled as round or rectangular ducts, with draw pits modelled as Mechanical Equipment in Revit. Key parameters such as System Type and Feature Type (Drainage / Sewerage) are specified, and the conventions are aligned with the HKIS Measurement Information Requirements.

Methodology. The central technical task is calculating the depth of the pipe invert along the alignment relative to the corresponding ground surface. In Civil 3D, the drainage network can be associated with a ground surface, allowing invert depth to be computed at every chainage. In Revit, where pipes and ducts are not associated with a surface — or where no ground surface is modelled — invert depth is derived by interpolation. From these depths the plug-ins apply the SMM itemisation rules, including the depth bandings that drive excavation items.

Development. The plug-ins extract raw data from model geometry and attributes (including property set values in Civil 3D), abstract that data according to the SMM, and output a Bill of Quantities. Selection of the drainage alignment and ground surface is made directly within the authoring software, and results have been demonstrated on both Civil 3D drainage networks for civil engineering works and Revit drainage and cable ducting for building works.

Deliverables

• Software plug-ins for Autodesk Civil 3D and Autodesk Revit
• Raw data extraction from model geometry and attributes
• SMM-compliant abstract and generated Bill of Quantities
• Defined modelling methods for drainage and cable duct networks
• Installation and operation manual
• Tools released for open use by the industry, free of charge

Benefits to the Industry

• Removes manual take-off for underground drainage and cable ducts, cutting the time and cost of preparing bills
• Produces consistent, standards-based itemisation that is repeatable and easier to audit
• Reuses information already present in BIM models, strengthening the case for modelling underground utilities to standard
• Improves alignment between designers, modellers and quantity surveyors through clearly defined modelling conventions

Frequently Asked Questions

Which software and versions are supported? Autodesk Civil 3D 2024 and Autodesk Revit 2024.

Which services can be measured? Drainage pipes and manholes, and cables and ducts, for both civil engineering works and building works.

Which standard methods of measurement does the output follow? Section 5 of the SMM for Civil Engineering Works, SMM5 for Building Works, and the ASD Model Bill.

Do I have to model in a particular way for the plug-ins to work? Yes. The tools rely on defined modelling conventions — for example, Pipe Networks in Civil 3D, DSD manhole families, and draw pits modelled as Mechanical Equipment in Revit — together with parameters such as System Type and Feature Type. These conventions are set out in the operation manual and align with the HKIS Measurement Information Requirements.

What if the ground surface is not modelled? In Civil 3D the network is associated with the ground surface, so invert depth is calculated at every chainage. In Revit, where no surface association exists, invert depth is derived by interpolation between known levels.

Is the software free to use? Yes. Any industry stakeholder may use the software free of charge.

How do I obtain the plug-ins and the manual? Please contact the CIC. An installation and operation manual is provided with the software.

Is training or a demonstration available? Demonstrations covering Civil 3D drainage networks and Revit drainage and cable ducting have been prepared. Please contact the CIC for details.

Research Team

• Prof. Jack Cheng, CCBM — Professor in Civil Engineering, HKUST
• Ir C K Ng, MICE / CCBM — Director, Build.IT / dRoW