Note: This article is written and published in Spanish and is a translated version of the original.
In this article we will discuss the ideal or normative use of classification systems Uniformat, MasterFormat and OmniClass in Revit, based on their original definition, their formal structure and their application throughout the life cycle of a BIM project.
We know that in practice many offices adapt these systems to their specific needs, reuse fields, combine structures or even omit certain classifiers for simplicity or local context. If you choose to do so, that's okay: each workflow can and should evolve depending on your goals and resources.
However, knowing the ought to be allows you to make informed decisions, justify your strategy to other teams or institutions, and improve interoperability with other platforms and standards.
Where do these classification systems come from?
Why were they created?
In the construction industry, the management of technical information has always been a challenge: multiple actors, extensive documents, different levels of detail and ambiguity in interpretation. Classification systems arise to solve three key problems:
- Standardize technical language between architects, engineers, builders, and customers.
- Facilitate the organization and consultation of technical information (specifications, costs, plans, maintenance).
- Improve communication and traceability in technical documents and control systems.
How are they born?
Uniformat
- Powered by: ASTM (American Society for Testing and Materials) in the 1970s.
- Motivation: Allow cost estimates and comparison between construction systems from early stages.
- Originally not intended for BIM, but for preliminary budgets and scheduling of work by systems.
MasterFormat
- Powered by: CSI (Construction Specifications Institute) and CSC (Construction Specifications Canada).
- Year: First version in 1963; Modern version (50 divisions) in 2004.
- Motivation: Standardize material specifications, execution methods, and construction activities in contractual documents
- Widely used in North America, especially for construction specifications.
OmniClass
- Powered by: CSI in conjunction with the OCCS Development Committee, published in 2006.
- Motivation: To create a multidimensional system, compatible with international standards (ISO 12006-2), that could classify everything that exists in a built environment: products, functions, spaces, processes, documents, actors, etc.
- Designed from the outset for digital environments and databases, but not exclusively for BIM.
Can they be used outside of BIM?
Yes. In fact, this is how they were born:
Although deeply integrated into BIM today, these systems are still useful in analogue or hybrid processes such as databases, Excel budgets or printed documentation.
You don't need to use Revit or BIM software to apply these classifiers. But when you use BIM, they become essential to harness their full potential.
So, what are classification systems?
They are hierarchical structures that bundle information about elements, products, activities, features, and spaces in the built environment. In Revit, they are used to categorize objects and facilitate:
- Technical Documentation
- Budgets and Costs
- Specs
- Interoperability
- Asset Management & Maintenance
Building Lifecycle Relationship
In BIM, the building lifecycle is divided into key phases:
- Planning & Predesign
- Design (Schematic, Detailed, and Construction)
- Construction & Assembly
- Operation & Maintenance
- Demolition or Reuse
Uniformat: Sorting by functions or systems
What is it?
Uniformat (ASTM E1557) classifies elements by functional systems such as foundation, structure, envelope, finishes, etc.
How is it structured?
- A100: Substructure
- B100: Superstructure
- C100: Surround
- Ex: B2010 - External walls
How is it used in Revit?
- Using the Assembly Code
- Great for system families such as walls, floors, ceilings, etc.
- Useful for preliminary budgeting by systems
When does it apply?
- Early project phase, especially schematic design.
- Estimates by system.
- Competitions or tenders with conceptual scope.
MasterFormat: Sorting by products and materials
What is it?
MasterFormat (CSI/CSC) organizes components by building products and activities. It is widely used in technical specifications and detailed quotes.
How is it structured?
- 50 divisions (ex: 03 – Concrete, 09 – Finishes, 26 – Electrical)
- Ex: 09 65 13 – Carpet rugs
How is it used in Revit?
- Using Keynote
- It can also be loaded as a custom parameter or into loadable families
- Links to specifications and price catalogs
When does it apply?
- Detailed design
- Construction documentation and construction work
- Generation of catalogs and budget items
OmniClass: Comprehensive and multidimensional classification
What is it?
OmniClass is a classification matrix based on 15 tables. It allows you to organize everything from products, processes,spaces, to information and roles. It is aligned with standard ISO 12006-2.
Most commonly used tables in Revit:
- Table 21 –Elements (similar to Uniformat)
- Table 22 –Work Results (similar to MasterFormat)
- Table 23 –Products
- Table 13 –Spaces
- Table 36 –Information
How is it used in Revit?
- Revit adds the fields OmniClass Number and OmniClass Title by default
- Can be customized per family type
- Used for models with high interoperability demands (COB ie, FM, IFC)
When does it apply?
Inproject lifecycle but especially:
- Complex collaborative environments
- Linking to CDEs,COBie,Facility Management
- Multiple or International Classifications Requirements
Why rank them during the BIM lifecycle?
- Design: Estimate, Compare Systems, Justify Choices
- Construction: Link to line items, work tracking
- Operation: Locate assets, plan maintenance, costs per component
- Interoperability: Connect to external software (Archibus, Planon, iTWO, etc.)
- Regulations: Compliance with national and international standards
How to assign these codes in Revit?
Uniformat:
- Select the element
- Go to Type Properties
- Find the fields:
- Assembly Code → Uniformat
Revit will automatically show you the sections in the tables that support the category of the selected element. You will be able to assign the classification that best corresponds, and to the code level you need.
Master Format
Master Format is managed from three different points: By Element, by Material and by User Defined Key. In Revit this is more commonly known as key notes:
To load as an item:
- Select the element
- Go to Type Properties
- Find the fields:
- Keynote → KeyNotes
As material:
- Manage menu
- Materials
- Panel Identity
- Revit Annotation Information → Keynote
As a user:
Use the User Keynote mode to tag an item. Example: Label wall in plan:
As soon as you place the label, the software will unfold the tables for you to assign a classification:
Note: This is the least recommended method, since you're not actually classifying the item, you're just overlaying a label with a rating on it. The information is not really tied to the item.
A very important part to keep in mind with Keynotes is that the file on which they are based from the beginning is just an example Keynotes file that Autodesk includes by default in the installation of Revit (usually in the Libraries folder). Its purpose is to demonstrate how the Keynotes system works but does NOT directly represent any complete official classification system such as MasterFormat or Uniformat.
What does it actually contain?
- It is a hierarchical list of codes and descriptions.
- Some codes resemble the Masterformat format (e.g. 03 30 00 Concrete Cast in-Place),
but:
- This is not a complete or up-to-date implementation of the Masterformat (However, this is where it would be implemented).
- Some entries mix generic categories with arbitrary trade names or codes.
- It's intended more as a base template for you to adapt than an out-of-the-box standard.
OmniClass
The Omniclass is natively present when creating a family. If you select a specific template to create your family, by default it will already have an Omniclass code assigned to it. If this is not the case (Generic Template) you will have to upload it manually:
In System families it is not present, however, by means of shared parameters (a topic that we will touch on in a later article) we can assign it without problem.
Conclusion
Uniformat, MasterFormat, and OmniClass do not compete with each other: they complement each other and their coordinated use improves data management, interoperability, and BIM model maintenance. Applying them properly throughout the building lifecycle ensures that the model is not only visual, but smart, useful, and reliable for everyone involved.
It has been a pleasure to accompany you in this article, if you found it interesting and useful, don't forget to like it and share it. Maybe it will work for someone else. Likewise, I invite you to comment on it and if you are interested in the development of a topic, please gladly request it in the comments and we will contemplate it for future publications.
Note: This article is written and published in Spanish and is a translated version of the original.
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