How UniFormat and MasterFormat differ

The whole difference in one line

UniFormat organises a building by element. MasterFormat organises it by the work of building. Everything else is a consequence.

ASTM E1557-09(2020)e1, the standard behind UNIFORMAT II, defines elements as "major components common to most buildings" that "usually perform a given function, regardless of the design specification, construction method, or materials used." The NIST report that formed the technical basis for the standard gives the examples: foundations, exterior walls, sprinkler systems, and lighting.

MasterFormat cuts the same building differently. It provides a master list of divisions and sections that organises information about a facility's construction requirements and the activities that go with them. NIST, comparing the two formats, calls it "a classification that is based on products and materials". The industry term for what one of its sections names is a work result, the same classification OmniClass carries as its Table 22, Work Results. A work result is not a part of a building. It is a defined body of work, specified in one place, that someone can be asked to price and perform.

So an element exists the moment you decide the building has one. A work result does not exist until you have decided what it will be made of and how it will be bought. That is why the two systems belong at different points in a project, and why neither is a better version of the other.

Publishers, numbering, and the names

Two publications carry the UniFormat name. ASTM E1557-09(2020)e1 is titled "Standard Classification for Building Elements and Related Sitework—UNIFORMAT II". CSI has published its own document under the name; NIST cites the 1998 edition as "UniFormat: A Uniform Classification of Construction Systems and Assemblies". Both descend from the same 1970s work. NIST records that Hanscomb Associates developed an elemental format called MASTERCOST for the American Institute of Architects in 1973, that the General Services Administration was developing one called UNIFORMAT, and that the two bodies agreed on a common format. ASTM approved E1557 in 1993 and revised it in 1997.

MasterFormat is published by the Construction Specifications Institute with Construction Specifications Canada. Earlier editions used 16 divisions. The 2004 edition expanded that to 50; the current published listing runs to Division 48.

UniFormat codes are a letter followed by digits, read left to right down the hierarchy. The seven Level 1 Major Group Elements are A Substructure, B Shell, C Interiors, D Services, E Equipment and Furnishings, F Special Construction and Demolition, and G Building Sitework. Level 2 gives Group Elements such as B20 Exterior Enclosure; Level 3 gives Individual Elements such as B2010 Exterior Walls. The 1997 edition had 57 Level 3 building elements and 22 Level 3 sitework elements. The current standard defines three levels and places a suggested fourth, of sub-elements, in an appendix.

MasterFormat numbers are six digits in three pairs. The first pair is the division; the pairs after it narrow the work. Section 09 29 00 Gypsum Board sits in Division 09 Finishes; Section 08 11 13 Steel Doors and Frames sits in Division 08 Openings. What goes inside a section, Part 1 General, Part 2 Products and Part 3 Execution, is set by a separate CSI document, SectionFormat.

Both are copyrighted and sold. Two free public routes to the structures themselves are NISTIR 6389, which reproduces the E1557-97 charts, and the Unified Facilities Guide Specifications, a set of US government construction specifications published section by section under MasterFormat numbers and titles.

Where each sits in the life of a project

The NIST report sets out the mapping between project stage and format directly. Program and schematic documents are structured by UNIFORMAT II. Design development and construction documents are structured by MasterFormat.

The reason is economic rather than administrative. NIST puts it this way: "a cost estimate prepared using a format based on a listing of products and materials is time consuming, costly, and inappropriate at the early design stages. Yet, it is in the early stages of design that economic analysis is most important in establishing the economically efficient choices among building alternatives."

The switch point is not a date. It is the moment the design has committed to enough product and assembly decisions that a section number can be written without inventing them.

One partition through both systems

Take a non-load-bearing interior partition: metal studs, gypsum board both sides, fire-rated penetrations, one steel door, painted.

In UniFormat it sits under C Interiors, then C10 Interior Construction, then C1010 Partitions. The board integral to the partition stays there. The published exclusion list sends applied wall finishes out to C3010 Wall Finishes, and C3010 in turn excludes wallboard integral to interior walls and partitions. The door does not stay with the partition either: doors, frames, hardware and door painting all go to C1020 Interior Doors. If that same wall carried load it would leave C1010 for B10 Superstructure, because its function changed.

In MasterFormat the same partition is scattered across four divisions. Each of the numbers below is a published MasterFormat section number and title.

Notice the studs. Non-load-bearing wall framing for gypsum board is specified in Division 09, alongside the board it supports; the government guide specification for 09 22 00 covers non-load-bearing wall framing and furring. Load-bearing cold-formed metal framing is specified in Division 05, alongside structural steel, and the guide specification for 05 40 00 carries a clause on load-bearing cold-formed metal framing. The steel can be the same gauge either way. The classification changes because the work is specified, submitted and bought differently.

Both systems draw a line at load-bearing walls, but in different places and for different reasons. UniFormat moves the wall because it performs a different function. MasterFormat moves the studs because they are a different piece of work.

Why a crosswalk can only be approximate

Mapping tables between the two systems exist and are useful. NIST reproduces one taken from the AIA's Architect's Handbook of Professional Practice, a matrix of elements against the sixteen divisions then in use. NIST flags in a footnote that this matrix maps the original UNIFORMAT rather than UNIFORMAT II. The problem is visible on the page regardless: the row for Partitions carries marks in several divisions, and single divisions collect marks from several elements. The relationship is many-to-many in both directions.

A one-to-one crosswalk would require that each element be built from exactly one kind of work, and that each kind of work appear in exactly one element. Neither holds. Painting appears in wall finishes, in doors, in floors and in ceilings. A partition draws on framing, on board, on firestopping and on coatings.

NIST makes the timing consequence explicit. Its elemental estimate tables carry a column for the output code, used for sorting line item costs into other breakdowns "such as by MasterFormat 95; by construction trades, bid packages, or functional areas". That column is blank in the worked example, and the stated reason is that "at the early stage of design, which these tables portray, the assemblies and elements have not yet been designed in detail."

The code cannot be assigned because the decision that would determine it has not been made. A crosswalk applied before that point is a guess about a design decision, dressed as a lookup.

The cost of using the wrong one

Reaching for MasterFormat too early forces product decisions that the design has not made. To write a section number you must name the work, and to name the work you must pick materials and a way of buying them. The resulting document reads as though those choices are settled. It is also slower to produce and harder to revise, at exactly the stage when alternatives are still being compared.

Reaching for UniFormat too late leaves the project without documents that anyone can bid or build from. Outline specifications and construction specifications are organised by MasterFormat section, and the paperwork follows. The US government's submittal procedures section states that submittal requirements are specified in the technical sections, so the submittal register is assembled section by section. An element-organised list does not tell a drywall subcontractor whether the door frames are theirs.

There is a quieter cost too. Elemental figures are comparable across projects because every building has exterior walls and partitions regardless of how the work was procured. Work-result figures are comparable only across projects that were packaged the same way. Early benchmarking against past projects works in UniFormat and degrades in MasterFormat.

Names that get confused

UNIFORMAT, without the II, is the original GSA and AIA classification. NIST records that it never gained standard status or federal recognition, and that it is nonetheless the basis of most elemental formats used in the United States. It ran to seven levels of definition, extending down to products and materials, and older cost tables still use its numbering.

UNIFORMAT II is the ASTM version, E1557. UniFormat is the CSI publication of the same family. They share the element logic and the broad structure, but editions differ: the 1997 ASTM classification changed the 1992 NIST version by adding an alphanumeric designator system and five years of consensus revisions. Check which document a cost database or a specification actually uses before comparing figures.

CSI also publishes OmniClass, which it describes as a classification structure for electronic databases and software, and SectionFormat, which gives guidance on organising and formatting the text of specification pages rather than classifying anything.