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Implementation of Reality Modeling in Renovation Projects

Author: Century 3       Update: 2020-03-04

By Ken Jin, Director of BIM Center

If we fail to find the original as-built drawing of a facility, or the structure and MEP of the facility are not correctly presented on the as-built drawings, is it possible to use modern technology to re-build a 3D model detailing the facility’s structural, mechanical and electrical elements for a retrofit project, enabling the engineers to achieve better design quality? The answer is Yes! In the following project example, you will find out how to solve the problem by 3 steps.

The project illustrated in the below picture is a single-story shelving structure building. Built around the year of 1995 with both of its architectural and structural drawings missing, the facility has been used as a warehouse and now will be repurposed for manufacturing workshop. With a 1.4m height difference between interior and exterior, the facility is 67.5m in length and 36m in width at the height of 10.3m. The grid spacing is 7.5m by 18m. The building footprint area is 2482.0m², and the gross floor area is 2482.0m².

Scope of Renovation Marked in Yellow

This renovation project is challenged with the absence of the original as-built drawing and a tight schedule that allows only 4 weeks for design phase. The measurement of the field and its surroundings, the building’s elements i.e., walls and beams can only be carried out by site survey, which requires at least three professionals to work on-site for an estimated one week. Therefore, Century 3 decided to implement 3D laser scan technology for on-site data collection, then create the as-built model for the upcoming renovation design.

1. Data Collection through 3D Scan

We adopted 3D reality scan for on-site data collection so as to achieve good site survey quality on schedule. Two professionals were designated on-site including one scanning specialist and one assistant. Overall, 40 location points inside the facility were covered by 3D scan within only one day.  

Two Staff Working On Site

2. Reverse Modeling

Up to 30GB’s aggregated magnitude of points cloud data was collected for this 2482-square-meter facility. The point cloud information was firstly formatted in RCS, compressed down to 6GB for Revit input and eventually displayed in engineers’ computer as a point-cloud-based 3D model. Based on this particular model, modeling engineers were able to establish an as-built model in Revit, incorporating beams, walls, doors, windows, roofing and partial pipeline of the building. Meanwhile, engineers of all disciplines were ready to start the renovation design based on this Revit model.

Geometric size and location data of building elements are collected by laser through scanning the interior of the facility, providing a complete and reliable information source for the upcoming renovation design.

Reverse Modeling Based on Point Cloud Information

3. Examination

After the Revit model was built, further examination through comparison of site photos and point clouds was required to ensure the Revit model is in accordance with the reality in terms of scale and geometric location. The completion of this step announced the official start of the renovation design.

Overlay of the Model and Point Cloud

The authentic on-site information was reproduced and restored digitally through the combination of 3D reality scan and reverse modeling using the minimum manpower and time. This method significantly reduced design errors caused by inaccurate measurement and laid a solid foundation for the renovation design.


Century 3 has successfully accomplished a couple of similar renovation projects in Hong Kong and Southeast Asia. The development of 3D technology offers new solution to the renovation of old facilities whose original as-built drawings are oftentimes inaccurate or incomplete. 3D reality scan is unique in its fast acquisition of visual, editable and accurate data, which are saved in formats adaptable to various BIM software. Besides, the 3D scan technique can make up for BIM’s deficiency in on-site data collection with accuracy and efficiency. Through reverse modeling and data application tailored for individual projects, the implementation of BIM technique is widely adopted in the renovation project design.