BIM for As built

How to digitise properties and get to As Built in the public sector

The public sector faces a challenge in managing outdated, inaccurate, or unavailable building information. This can lead to costly setbacks and in severe cases, even fatal consequences. Building Information Modelling (BIM) can resolve these challenges by structuring information and creating 3D models for buildings. However, BIM models can often be unreliable if created from outdated 2D drawings or errors in laser scans. A solution is to compare the BIM models against laser scans to ensure As Built accuracy. Two Norwegian counties are using Imerso's solution to digitise their buildings and keep building plans up-to-date. With Imerso's cloud-based solution, facility managers and students can easily store 3D scan data and collaborate online, allowing for better control of building assets.

Written by Frederico Valente
Updated: March 14, 2023
BIM, As Built

Table of Contents

Take control by combining BIM and laser scanning

How can we get useful 3D BIM models for our existing buildings?


Take control by combining BIM and laser scanning

A common challenge in the public sector, which owns and manages a vast number of buildings and square meters across wide territory, is that one has to deal with outdated, inaccurate, or plain simply unavailable building information.

As Built information based on older drawings and documents is often unreliable and lacking. Simple 2D drawings might be wrong or missing recent changes made to the buildings, resulting in costly setbacks. These range from a wrong basis to be used in project planning, redesign and tendering processes, to inefficient operation and maintenance workflows throughout the building life-cycle.

Even key data like the area of your buildings, or vacated space is highly unreliable and you're probably paying for space you don’t have. Likewise, you might be missing out on rental income for space you didn’t know you have. In some cases, unreliable documentation can lead to severe consequences (see image below on the example of undocumented partition walls blocking the expected fire-escape route).
Map of a construction site that shows where deviations occur. On the image, a wall and doors block emergency escape routes

Outdated documentation can in the worst case be fatal

Over the last years, the introduction of building information modelling (BIM) across the construction industry has promised to resolve these challenges.

By structuring important and useful information together with object-oriented 3D models, BIM enables to optimise the way buildings can be operated: reducing waste, energy, time, money and risk across the building life cycle.

How can we get useful 3D BIM models for our existing buildings?

There are basically two ways to go:

  • either creating basic BIM models out of the existing 2D drawings, or
  • laser-scanning the existing buildings and creating BIM models directly out of the laser scan data.

Both, however, have their pitfalls.

When creating 3D Models (BIM) from outdated 2D drawings, all the outdated information is replicated and the model itself ends up not providing the value intended. Similarly, when BIM models are created out of laser scans, errors and overlooked misplacements, such as imprecise modelling and missing elements, happen frequently and remain overlooked.

Image of a construction site in 3D view. Imerso highlightes deviations in pipes location between reality and BIM plansMismatches between model and reality happen frequently

The solution to avoid these pitfalls is a tool that efficiently compares the created BIM models against laser scans of the respective buildings and highlights all deviations.

The created models can be tested for their As Built accuracy and any errors can be corrected.

Then, the resulting BIM models can work as reliable replicas of the buildings.

At the forefront of adopting 3D scanning to digitise existing buildings and to keep the building plans up-to-date, are the two Norwegian counties Møre og Romsdal and Vestland Fylkeskommune.

Using Imerso as part of their digital twin strategy, they ensure that their building plans are accurate and the data shared with consultants, contractors and other third parties are reliable. To facilitate laser scanning and make it possible to roll it out over many properties, Imerso has an integrated feature that lets anyone do laser scanning, without having to be an expert in this field.

Image showing a heatmap functionality in Imerso, where construction deviations from the BIM plans are displayed. Imerso highlights all deviations between reality and the plans

Now, facility managers, as well as students during their summer jobs, can take over this part. Because Imerso’s solution is cloud-based and works with open file formats, the teams can easily use the solution to store 3D scan data, collaborate across teams online and exchange data with other systems.

All this enables the project manager or facility manager to have better control of the building assets at any given time — and verify how well the models reflect the current reality of the property.

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