What Information Should an As-Built BIM Model Contain? A Practical Project Guide

What Should an As-Built BIM Model Include? A Practical Guide for Construction Projects

An AS-built BIM model should do more than show what an existing building looks like.

For renovation, refurbishment, facility upgrades and future construction, project teams need reliable information about the building as it exists today. This can include geometry, dimensions, equipment, MEP services, materials, locations and other information required for the next stage of work.

This is where As-Built BIM Modelling becomes valuable.

Instead of relying entirely on old drawings or manual measurements, an as-built model can bring existing building information into a structured digital environment. Depending on the project requirements, information can be developed from site surveys, laser scanning, point clouds, existing documentation and other available sources.

But what should actually be included in an as-built BIM model?

The answer depends on the purpose of the model. A model prepared for an HVAC upgrade will have different requirements from one created for facility management or a major refurbishment project.

What is an As-Built BIM Model?

An as-built BIM model is a digital representation of a building based on its actual existing conditions.

The model can document elements that are currently installed rather than simply representing the original design intent.

Depending on the project scope, this may include:

• Architectural elements
• Structural elements
• HVAC systems
• Mechanical equipment
• Ductwork
• Pipework
• Electrical services
• Fire services
• Building openings
• Ceilings
• Plant rooms
• Equipment information
• Relevant asset data

The important point is that an as-built model should be developed around the intended use of the model.

There is no universal list of information that every project needs.

1. Accurate Building Geometry

The foundation of an as-built BIM model is accurate geometry.

This can include:

• Walls
• Floors
• Ceilings
• Roofs
• Doors
• Windows
• Columns
• Beams
• Stairs
• Shafts
• Openings

For existing buildings, geometry can be established using available drawings, site measurements, 3D laser scanning, point clouds or a combination of these sources.

Accurate geometry gives designers and contractors a reliable starting point when planning modifications.

For example, if a new mechanical system needs to be installed in an existing ceiling space, the design team needs to understand the actual ceiling height, structural elements and available service zones.

2. Dimensions and Levels

An as-built model should contain relevant dimensional information required for its intended purpose.

This can include:

• Floor-to-floor heights
• Ceiling levels
• Wall locations
• Room dimensions
• Equipment dimensions
• Duct sizes
• Pipe sizes
• Service levels
• Opening sizes

Levels are particularly important for MEP coordination.

A duct may appear correctly positioned in plan view but still conflict with a structural beam or another service because of its vertical elevation.

Accurate three-dimensional information helps teams understand these relationships.

3. Existing HVAC Information

For projects involving mechanical services, HVAC information can be one of the most important parts of an as-built model.

Depending on the scope, the model may include:

• Supply air ductwork
• Return air ductwork
• Outside air systems
• Exhaust ductwork
• Diffusers
• Grilles
• Fans
• Air handling units
• Fan coil units
• Mechanical plant
• Dampers
• Louvres
• Other HVAC components

The model can document the location and geometry of existing services so that proposed modifications can be developed around actual site conditions.

This is particularly useful during HVAC upgrades and refurbishment projects.

4. Mechanical Equipment Information

Equipment should not necessarily be represented only as a generic 3D shape.

Where the required information is available, an as-built BIM model can include details such as:

• Equipment name
• Equipment tag
• Manufacturer
• Model number
• Dimensions
• Location
• Equipment type
• Capacity
• Connection information
• Relevant technical data

The exact parameters depend on the project’s BIM requirements.

For example, a plant-room model may need more equipment information than an architectural model created primarily for renovation planning.

5. MEP Services and Connections

Existing buildings can contain a large number of interconnected services.

An as-built model may need to capture relevant:

• HVAC systems
• Plumbing
• Hydronic systems
• Electrical services
• Fire services
• Cable trays
• Pipework
• Mechanical connections

For MEP coordination, it is not enough to know that a service exists.

Its location, size, elevation and relationship with other services can also be important.

This information helps designers understand available space before introducing new services.

6. Room and Space Information

Rooms and spaces are another important component of an as-built BIM model.

Depending on the project, information may include:

• Room names
• Room numbers
• Room areas
• Room boundaries
• Floor levels
• Space classifications
• Ceiling heights
• Department or zone information

For commercial and healthcare projects, structured room information can be particularly useful when planning refurbishment or changes to building services.

7. Openings and Penetrations

Openings are easy to overlook but can have a major impact on construction.

An as-built model may document:

• Wall openings
• Floor penetrations
• Ceiling openings
• Service penetrations
• Structural openings
• Existing sleeves
• Access openings

This information can help determine whether new services can use existing penetrations or whether additional openings may be required.

For MEP projects, this can also support coordination with structural elements.

8. Materials and Construction Information

Depending on the project requirements, the model may contain information about materials and construction elements.

For example:

• Wall types
• Floor finishes
• Ceiling types
• Roof construction
• Door types
• Window types
• Insulation
• Duct materials
• Pipe materials

Not every project requires this level of information.

The required data should be determined by the BIM scope and intended application.

9. Asset Information

For facility management projects, asset information can become particularly important.

Assets may include:

• HVAC equipment
• Pumps
• Fans
• Electrical equipment
• Fire equipment
• Plant
• Controls
• Major building equipment

Relevant asset parameters can include:

• Asset ID
• Equipment type
• Manufacturer
• Model
• Serial number
• Installation information
• Maintenance information
• Warranty information

However, this information should only be included where it is available and required by the project.

An as-built BIM model should not present unverified information as confirmed data.

10. Spatial Relationships Between Building Elements

One of the major advantages of BIM is the ability to understand relationships between different building elements.

For example, the model can show how:

Ductwork → Structure → Ceiling → Lighting → Pipework → Cable Tray

interact within the same space.

This becomes especially useful when planning refurbishment work.

A proposed duct route can be reviewed against existing conditions before construction begins.

11. Existing Conditions from Point Clouds

When an as-built model is developed from 3D laser scanning or Scan-to-BIM workflows, the point cloud can provide the underlying reference for existing conditions.

The point cloud can help establish:

• Building geometry
• Equipment locations
• Duct routes
• Structural elements
• Service levels
• Complex spaces
• Existing installation conditions

However, the point cloud itself and the BIM model are not the same thing.

The point cloud provides captured spatial information, while the BIM model converts relevant information into structured and editable building elements.

12. Model Metadata and Parameters

A useful BIM model can contain more than geometry.

Parameters can be used to organise and describe model elements.

Depending on the project’s requirements, these may include:

• Element category
• System type
• Equipment type
• Asset number
• Manufacturer
• Model
• Location
• Classification
• Maintenance information

Consistent parameters make the model easier to search, schedule and manage.

13. Revision and Existing-Condition Information

Buildings change over time.

An as-built model may therefore need information about when the existing conditions were captured or when particular modifications were documented.

Depending on project requirements, this can include:

• Survey date
• Model revision
• Project stage
• Existing/proposed status
• Modification history
• Source information

Clear documentation helps users understand the context of the model.

14. Level of Detail and Level of Information

One of the most important decisions in an as-built BIM project is determining how much information is actually required.

A model does not automatically become better because it contains more geometry.

For example, a project may require:

Basic Existing Model
Building geometry and major elements.

MEP Coordination Model
Building geometry plus relevant HVAC, plumbing, electrical and other services.

Renovation Model
Existing conditions required for developing the proposed design.

Facility Management Model
Building elements plus structured asset and operational information.

The BIM requirements should be agreed before modelling begins.

What Should Not Be Added Without Verification?

Accuracy is not only about modelling what is visible. It is also about avoiding unsupported assumptions.

If a component cannot be confirmed from the available information, it should not automatically be represented as fact.

For example, if a concealed pipe cannot be verified through scanning, drawings or other reliable information, the model should not simply assume its exact route.

Clear documentation of assumptions and limitations helps users understand the reliability of the model.

How As-Built BIM Supports MEP Coordination

For MEP projects, accurate existing-condition information can significantly improve coordination.

Consider a commercial building where a new HVAC system is being introduced.

The design team may need to understand:

• Existing duct routes
• Structural beams
• Ceiling heights
• Existing pipework
• Cable trays
• Fire services
• Plant locations
• Existing penetrations

An as-built BIM model can bring these conditions into a shared environment.

The proposed system can then be coordinated against the existing building before installation.

As-Built BIM for Renovation and Refurbishment Projects

Renovation projects can be particularly challenging when existing documentation is incomplete.

A reliable as-built model can help teams:

• Understand existing conditions
• Plan new services
• Identify spatial constraints
• Review existing MEP routes
• Coordinate proposed changes
• Prepare construction documentation
• Reduce reliance on outdated drawings

This can be useful for commercial buildings, warehouses, healthcare facilities, industrial facilities, retail spaces and other existing structures.

As-Built BIM for Australian Projects

Australian construction projects often involve refurbishment, extensions, adaptive reuse and upgrades to existing buildings.

In these situations, accurate existing-condition information can be important for consultants, contractors and builders working on the next stage of construction.

The required model content will vary according to project scope, BIM standards and client requirements.

A practical approach is to define the information requirements before modelling begins and then develop the model around those requirements.

A Practical As-Built BIM Information Checklist

Before starting an as-built modelling project, project teams can consider the following:

Building

• Walls
• Floors
• Ceilings
• Doors
• Windows
• Structure
• Openings

MEP

• HVAC
• Ductwork
• Equipment
• Pipework
• Electrical services
• Fire services
• Cable trays

Information

• Equipment tags
• Dimensions
• Levels
• Manufacturers
• Model numbers
• Asset IDs
• Relevant classifications

Documentation

• Existing-condition drawings
• Model views
• Schedules
• Sections
• Equipment information
• Model revision information

The final checklist should always be adjusted to the project’s requirements.

How B&S MechDesign Supports As-Built BIM Modelling

B&S MechDesign provides BIM and drafting support for consultants, contractors and builders across Australia.

Our services include As-Built Modelling, Scan-to-BIM, Point Cloud to BIM, Revit Modelling, HVAC Modelling, Mechanical BIM, MEP Coordination and Clash Detection.

For existing-building projects, the focus is on developing practical BIM information that can support renovation, refurbishment, HVAC upgrades, MEP coordination and future construction activities.

The objective is not simply to create a detailed model. It is to create a model containing the right information for the way the project will actually use it.

Final Thoughts

An effective as-built BIM model should provide a reliable digital representation of the existing building and the information needed for its intended purpose.

Depending on the project, this may include building geometry, dimensions, levels, HVAC systems, MEP services, equipment, openings, rooms, materials and asset information.

The key is to define the requirements before modelling begins.

Whether the model is being created for an HVAC upgrade, commercial refurbishment, MEP coordination or facility management, the most useful as-built model is one that combines accurate existing conditions with structured, relevant information.

That makes the BIM model more than a digital representation of the building—it becomes a practical resource for planning what happens next.