CSI MasterFormat Divisions: The Complete List and How Estimators Use It

Since 2004, a MasterFormat number has six digits in three pairs, written with spaces between the pairs: 07 51 13. The first pair is the division, level 1. The second pair is level 2, the third pair level 3. A pair of zeros means that level is not used, so 07 50 00 is a level 2 number. Where more detail is needed, a fourth pair follows a decimal point: 07 51 13.13 is level 4. CSI's example runs from membrane roofing down to a cold-applied built-up asphalt roof, and the table below follows it.

A few rules from CSI's Applications Guide save a lot of confusion:

• Same places in every division. Operation and maintenance sits at XX 01 00, common work results (requirements shared by several sections of the division) at XX 05 00, schedules at XX 06 00 and commissioning at XX 08 00. In the facility services divisions, insulation sits at 2X 07 00 and instrumentation and control at 2X 09 00, which is why HVAC controls appear at 23 09 00.
• Numbers ending in zero are usually not assigned at levels 3 and 4, so that 11 14 43 is not mistaken for a child of 11 14 40. Assigned numbers mostly step by three: 13, 16, 19, 23, 26, 29.
• A number goes with its title, and only that title. Users may create new titles at levels 2 to 4 inside a division, at an unassigned number that fits the subject, but never inside a reserved division and never a new division.
• Display. Spaces between the first three pairs and a decimal point before level 4 is the recommended form; 07 5113.13 and 075113.13 are accepted variants. In software, keep whichever form you choose consistent.

Source: CSI and CSC, MasterFormat 2018 Introduction and Applications Guide, sections on expansion of the numbering system, assigned numbers, designated locations and display.

MasterFormat has two groups. The Procurement and Contracting Requirements Group is Division 00 alone. The Specifications Group holds Divisions 01 to 49 in five subgroups: General Requirements (01), Facility Construction (02 to 19), Facility Services (20 to 29), Site and Infrastructure (30 to 39) and Process Equipment (40 to 49). Of the 49 specification divisions, 15 are reserved for future expansion, which leaves 34 in use plus Division 00.

Source: CSI and CSC, MasterFormat 2018, Groups, Subgroups and Divisions and Master List; Applications Guide for the group structure. CSI's 2026 summary describes changes to listings inside divisions; check scope lines for Divisions 32 and 34 against the edition your project uses.

The subgroups follow a simple logic that is worth knowing by heart. Facility Construction (02 to 14) is the fabric of the building, from what is demolished to what is finished and furnished. Facility Services (21 to 28) is what used to be mechanical and electrical: fire suppression, plumbing, HVAC, automation, power, communications, security. Site and Infrastructure (31 to 35) is everything outside the building line and civil work in general. Process Equipment (40 to 48) serves industrial plants, water treatment and power generation, and rarely appears on a commercial building.

The other distinction people trip on is between Division 00 and Division 01. Division 00 holds the documents of the deal: the invitation, the bid form, the agreement, the bonds, the general and supplementary conditions. Division 01 holds the procedural rules every section of the specification relies on: how to submit, how to request payment, how substitutions, allowances, unit prices and alternates work, what temporary facilities are required, how the project closes out. Part 1 of each technical section extends Division 01 for its own subject rather than repeating it.

In a project manual's table of contents, CSI recommends listing every group and subgroup, and, inside any subgroup that is used, every division from its first to its last, with the unused ones, reserved divisions included, marked "Not Used". Sections are listed only if they are used. That is why a table of contents shows Division 24 even though nothing will ever be specified there.

A commercial building, an office, a school, a medical building or a retail shell, draws on the divisions in the table below and rarely on the others. Process equipment (40 to 48), transportation (34) and marine work (35) belong to industrial and civil projects. CSI's guide notes that cost databases organized on MasterFormat put bonds, insurance, permits and fees under Division 00, temporary facilities, mobilization and site administration under Division 01, and the cost of work results under the other divisions. The table lists what usually lands in each division on a building estimate, and the point where estimates most often go wrong.

Most contractors do not estimate in raw MasterFormat numbers. They keep a cost code list built on it, usually the division plus a level 2 or level 3 subject, with their own additions for general conditions, self-performed work and fees. That is fine, and CSI explicitly allows user-defined numbers inside a division as long as they do not reuse an assigned number for a different subject. The test of a good code list is whether every code can be traced back to one MasterFormat location, so that a line in the estimate can be checked against the section that governs it.

The free construction estimate template groups its lines by these divisions, with labels such as "03 Concrete" in its drop-down, and keeps a column for the drawing sheet and specification section each quantity comes from.

Many people still say "Division 15" for mechanical and "Division 16" for electrical. That vocabulary comes from the 16-division format, last published in the 1995 edition. CSI's Applications Guide explains why it was replaced: with one digit per level after the division, each division had room for only nine level 2 subjects, so topics went where there was space rather than where they belonged. Fire suppression, detection and alarm, lightning protection, and solar and wind equipment were all filed in Division 13 for that reason. The 2004 edition added a sixth digit, arranged the digits in pairs and moved building services into their own subgroup.

Source: Greg Ceton (CSI), Insulation Outlook, 2005; Consulting-Specifying Engineer, 2005; 1995 division list; CSI Applications Guide.

Two consequences for an estimator. First, an old cost database or a historical bid coded in five digits needs a crosswalk before it can be compared with a current estimate: 15xxx lines split three ways, 16xxx lines four ways. Second, a scope letter that says "Division 16 work" on a current project is ambiguous. Does it include data cabling (27) and fire alarm (28)? Name the divisions or the sections.

The three are often confused because CSI publishes all of them, but they answer different questions. MasterFormat asks what is being built, trade by trade. UniFormat asks what the building is made of, function by function: its foundations, its exterior walls, its heating, whatever they turn out to be made of. OmniClass is a wider set of tables for classifying construction information in databases and models.

There are two UniFormats. UNIFORMAT II is ASTM E1557, a standard classification of building elements and related sitework, first approved in 1993 and current as E1557-09, reapproved in 2020. It has three levels, major group elements, group elements and individual elements, plus a suggested fourth level in an appendix, and it states that it does not apply to major civil works and is unsuitable for process work or trade estimates. CSI UniFormat, published by CSI and CSC, uses the same lettered backbone with an Introduction category in front and a Z General category at the end. Its 2010 edition is still the stable edition in 2026: CSI's 2026 release added UniFormat material to its online platform but did not replace the 2010 edition.

Source: CSI and CSC, UniFormat 2010; The Construction Standard, OIR 26.1; ASTM E1557-09 (2020); RSMeans on UNIFORMAT II; CSI Applications Guide on OmniClass Tables 21, 22 and 23.

An exterior wall shows the difference. In UniFormat it is one element, B20 Exterior Vertical Enclosures, priced early as a cost per unit of wall area. In MasterFormat the same wall is spread over several divisions once it is designed: masonry or panels in 04 or 07, framing in 05 or 06, insulation and air barrier in 07, windows in 08, interior gypsum board and paint in 09. Neither view is wrong. The first tells an owner what the wall costs; the second tells a contractor who builds which part of it.

The two systems meet in the middle of a project. CSI's UniFormat guide shows MasterFormat numbers appended under a UniFormat element once a material is chosen, for example a subgrade wall element carrying 03 30 00 if it will be cast-in-place concrete or 04 20 00 if it will be unit masonry. And MasterFormat keeps a place for element-based performance requirements at 01 80 00, organized after UniFormat.

For UK work, neither applies: quantities are measured into a bill under RICS's NRM 2, the rules for detailed measurement of building works. See the NRM2 bill of quantities guide for that structure.

CSI's guidance is direct: UniFormat is most commonly used early, before work results have been selected, for preliminary project descriptions and preliminary cost estimates; MasterFormat organizes outline and full specifications, detailed cost data and drawing notations; and the right moment to switch is when work results are being chosen. ASTM E1557 says the same from the other side, positioning UNIFORMAT II for budgets and elemental cost plans before design begins, value engineering and early schedules.

The practical rule for a contractor: if the estimate will be checked against an owner's budget built on elements, keep an element view alongside the division view until the design settles. If the estimate will become a bid and then a budget, the division view wins, because subcontract bids, the submittal register and the schedule of values all speak in sections. The AI takeoff and estimating page covers how quantities feed that division view.

The real value of MasterFormat on a project is that one number can follow a piece of work through every document. The specification section is the anchor; everything else should point to it.

Source: CSI Applications Guide on drawing notations, cost data and trade jurisdictions; State of Missouri, Format for Construction Specifications on the three-part section.

The weak link is almost always the bid package. CSI is explicit that MasterFormat's structure does not imply how work is assigned to disciplines, trades or subcontractors, and that a trade is likely to work across several divisions. A drywall package can include sections from 05, 07 and 09; an electrical package may or may not include 27 and 28. Write each package as a list of section numbers, then check that every section in the project manual appears in exactly one package, or is deliberately excluded.

The same discipline applies downstream. The submittal log template keys every submittal to its specification section, and the schedule of values template works best when its lines carry the same codes as the estimate, so that billing reconciles to the budget line by line.

Most of the effort around MasterFormat on a bid is reading and sorting: which sections the project manual contains, which drawing notes belong to which section, which submittals each section asks for, which estimate lines have no section and which sections have no estimate line. That work can be prepared by software. The decisions that carry money and risk cannot.

This is the line Mirage works to on construction documents. Its agents read specifications and submittals and organize them into MasterFormat divisions and sections, each item traced to the clause it came from; cross-check specifications against the drawings on specification review; and keep the submittal register current on RFI and submittal tracking. Mirage has not published a deployment centred on MasterFormat classification. Its published construction results are on takeoff: at OCBM, 100% of quantities are tied to a source drawing, and at John Cockerill, piping takeoff takes 80 to 90% less time. If you are reorganizing a whole estimating process, the guide to automating an estimating department starts with the cost codes you already use.