OmniClass
A broad, multi-table framework for classifying everything about a building across its entire life.
Quick Answer
OmniClass is a multi-table classification system, maintained by the Construction Specifications Institute, designed to organize construction information across a building's entire lifecycle — from products and materials to work results, disciplines, and project phases. It incorporates other standards, including MasterFormat and UniFormat, as specific tables within its broader structure.
The Full Picture
OmniClass exists because no single classification system covers everything the AEC industry needs to tag and organize. MasterFormat handles trade-based specs; UniFormat handles building elements — but a BIM model, a facilities database, or a product library needs to classify information by discipline, phase, material, or space type too. OmniClass was built as an umbrella structure that all of these can plug into.
Mechanically, OmniClass is organized into 15 tables, each covering a different facet of construction information — Table 21 for Elements (based on UniFormat), Table 22 for Work Results (based on MasterFormat), plus tables for construction entities, spaces, disciplines, materials, and project phases, among others. Rather than replacing MasterFormat or UniFormat, OmniClass absorbs them as components and adds the tables needed to classify everything else.
In practice, OmniClass shows up most often in BIM environments, product data (such as manufacturer BIM object libraries), and facilities management systems, where consistent, machine-readable classification across a building's full lifecycle — design, construction, and operation — matters more than it does for a single discipline's day-to-day estimating or bidding.
For a GC's preconstruction team, OmniClass is rarely something they work in directly; it operates a layer above the trade-focused specs and bid packages they build day to day, more relevant to BIM authors, product manufacturers, and owners managing a building's data across its full lifecycle.
Real Examples
Common Misconceptions
People assume: OmniClass replaces MasterFormat and UniFormat.
Actually: It incorporates them. OmniClass Table 22 (Work Results) is based on MasterFormat and Table 21 (Elements) is based on UniFormat — OmniClass is a broader umbrella structure, not a competing replacement for either.
People assume: OmniClass is mainly for estimators and specifiers.
Actually: It's used far more in BIM authoring, product data libraries, and facilities management, where consistent lifecycle-wide classification matters. Day-to-day estimating and bidding lean on MasterFormat and UniFormat directly.
Frequently Asked Questions
What are OmniClass tables?
OmniClass is organized into 15 separate tables, each classifying a different aspect of construction — including entities, elements, work results, spaces, materials, disciplines, and phases — that can be used independently or combined.
How does OmniClass relate to MasterFormat?
OmniClass Table 22 (Work Results) is built directly on the MasterFormat numbering structure. Rather than duplicating it, OmniClass adopts MasterFormat as one of its component tables.
Who uses OmniClass?
Primarily BIM software vendors and modelers, product manufacturers building digital content libraries, and owners or facility managers organizing building data for long-term operations — less so estimators doing day-to-day trade-based work.
Is OmniClass required on construction projects?
No. It's most commonly specified on BIM-intensive or facilities-management-focused projects where the owner wants consistent classification across the building's full lifecycle; many projects never reference it directly.
Who maintains the OmniClass standard?
The Construction Specifications Institute (CSI), in coordination with other organizations whose standards feed individual tables, such as the developers of MasterFormat and UniFormat.