CSI MasterFormat: The Complete Reference Guide to Construction Divisions
A clear, practical guide to CSI MasterFormat divisions and numbering. Understand how construction specifications are organized with our complete division reference.
MasterFormat is the construction industry's standard for organizing specifications. This guide is your quick reference for CSI divisions and numbering.
Looking for a specific division? Jump to Complete Division Reference or use Ctrl+F to search this page.
Quick Reference: Common Divisions
For everyday construction work, these are the divisions you'll use most:
| Division | Name | Common Use |
|---|---|---|
| 01 | General Requirements | Submittals, quality control, temporary facilities |
| 03 | Concrete | Foundations, slabs, structural concrete |
| 05 | Metals | Steel framing, stairs, railings |
| 06 | Wood, Plastics, Composites | Framing, trim, casework |
| 07 | Thermal & Moisture Protection | Roofing, waterproofing, insulation |
| 08 | Openings | Doors, windows, hardware |
| 09 | Finishes | Drywall, flooring, paint, ceilings |
| 22 | Plumbing | Fixtures, piping, drainage |
| 23 | HVAC | Heating, ventilating, air conditioning |
| 26 | Electrical | Power distribution, lighting |
Need the full list? See Complete Division Reference below.
The Numbering System
MasterFormat uses a six-digit code formatted as XX YY ZZ:
| Digits | Represents | Example |
|---|---|---|
| XX | Division | 03 = Concrete |
| YY | Section | 30 = Cast-in-Place |
| ZZ | Subsection | 00 = General |
Examples
03 30 00 = Division 03 (Concrete) → Section 30 (Cast-in-Place) → General
09 91 00 = Division 09 (Finishes) → Section 91 (Painting) → General
06 41 93 = Division 06 (Wood/Plastics) → Section 41 (Architectural Casework) → Subsection 93 (Cabinet Hardware)
Some codes add a decimal for more detail: 03 01 30.51 = Cleaning of Cast-in-Place Concrete
Complete Division Reference
MasterFormat organizes all construction work into 50 divisions (00-49). Some numbers are reserved for future use.
Procurement and Contracting Requirements Group
| Division | Name | What It Covers |
|---|---|---|
| 00 | Procurement and Contracting Requirements | Bidding requirements, contract forms, conditions of the contract |
General Requirements Subgroup
| Division | Name | What It Covers |
|---|---|---|
| 01 | General Requirements | Project-wide requirements: administrative, procedural, temporary facilities, quality control |
Facility Construction Subgroup
| Division | Name | What It Covers |
|---|---|---|
| 02 | Existing Conditions | Site assessments, surveys, demolition, hazardous material remediation |
| 03 | Concrete | Formwork, reinforcing, cast-in-place, precast, grouting |
| 04 | Masonry | Brick, block, stone, glass unit masonry, veneer |
| 05 | Metals | Structural steel, metal fabrications, metal decking, railings |
| 06 | Wood, Plastics, and Composites | Rough carpentry, finish carpentry, architectural woodwork, plastic fabrications |
| 07 | Thermal and Moisture Protection | Waterproofing, insulation, roofing, siding, joint sealants |
| 08 | Openings | Doors, windows, hardware, glazing, louvers |
| 09 | Finishes | Plaster, gypsum board, tile, flooring, ceilings, painting |
| 10 | Specialties | Signage, lockers, fire extinguishers, toilet accessories, partitions |
| 11 | Equipment | Commercial equipment, food service, athletic, parking, loading dock |
| 12 | Furnishings | Artwork, window treatments, furniture, rugs, plants |
| 13 | Special Construction | Swimming pools, ice rinks, kennels, special-purpose rooms |
| 14 | Conveying Equipment | Elevators, escalators, lifts, dumbwaiters, cranes |
| 15 | Plumbing + HVAC | Alternative location for mechanical trades (see also Div 22-23) |
| 16 | Electrical + Lighting | Alternative location for electrical trades (see also Div 26) |
| 17-19 | (Reserved) | Reserved for future expansion |
Note: Divisions 15-16 exist for compatibility with the older 16-division format. Modern specs typically use Divisions 20-28 instead.
Facility Services Subgroup
| Division | Name | What It Covers |
|---|---|---|
| 20 | Mechanical Support | Mechanical support, hangers, vibration control |
| 21 | Fire Suppression | Sprinklers, standpipes, fire pumps, fire extinguishing systems |
| 22 | Plumbing | Fixtures, domestic water, sanitary waste, storm drainage |
| 23 | HVAC | Heating, ventilating, air conditioning, ductwork, controls |
| 24 | (Reserved) | Reserved for future expansion |
| 25 | Integrated Automation | Building automation systems, integrated control |
| 26 | Electrical | Power distribution, lighting, wiring devices, generators |
| 27 | Communications | Data, voice, audio-video, paging, intercoms |
| 28 | Electronic Safety and Security | Access control, surveillance, detection systems, alarms |
| 29 | (Reserved) | Reserved for future expansion |
Site and Infrastructure Subgroup
| Division | Name | What It Covers |
|---|---|---|
| 30 | (Reserved) | Reserved for future expansion |
| 31 | Earthwork | Grading, excavation, shoring, soil treatment, tunneling |
| 32 | Exterior Improvements | Paving, curbs, fencing, irrigation, site furnishings |
| 33 | Utilities | Water, sanitary sewer, storm drainage, gas, electrical utilities |
| 34 | Transportation | Railroads, airfield paving, bridges, tunnels |
| 35 | Waterways and Marine Construction | Dredging, dams, piers, seawalls, marine equipment |
| 36-39 | (Reserved) | Reserved for future expansion |
Process Equipment Subgroup
| Division | Name | What It Covers |
|---|---|---|
| 40 | Process Interconnections | Process piping, instrumentation, valves for industrial facilities |
| 41 | Material Processing and Handling Equipment | Conveyors, cranes, hoists, storage equipment |
| 42 | Process Heating, Cooling, and Drying Equipment | Boilers, furnaces, dryers, kilns |
| 43 | Process Gas and Liquid Handling, Purification and Storage Equipment | Tanks, pumps, compressors, filters |
| 44 | Pollution Control Equipment | Air pollution control, emissions treatment |
| 45 | Industry-Specific Manufacturing Equipment | Food processing, textile, printing equipment |
| 46 | Water and Wastewater Equipment | Treatment systems, pumps, filters |
| 47 | (Reserved) | Reserved for future expansion |
| 48 | Electrical Power Generation | Generators, turbines, solar, wind equipment |
| 49 | (Reserved) | Reserved for future expansion |
Example Sections Within Divisions
Division 03: Concrete
| Section | Name |
|---|---|
| 03 10 00 | Concrete Forming and Accessories |
| 03 20 00 | Concrete Reinforcing |
| 03 30 00 | Cast-in-Place Concrete |
| 03 31 00 | Structural Concrete |
| 03 38 00 | Post-Tensioned Concrete |
| 03 40 00 | Precast Concrete |
| 03 50 00 | Cast Decks and Underlayment |
| 03 60 00 | Grouting |
| 03 70 00 | Mass Concrete |
| 03 80 00 | Concrete Cutting and Boring |
Division 09: Finishes
| Section | Name |
|---|---|
| 09 20 00 | Plaster and Gypsum Board |
| 09 29 00 | Gypsum Board |
| 09 30 00 | Tiling |
| 09 50 00 | Ceilings |
| 09 60 00 | Flooring |
| 09 63 00 | Masonry Flooring |
| 09 65 00 | Resilient Flooring |
| 09 68 00 | Carpeting |
| 09 90 00 | Painting and Coating |
| 09 91 00 | Painting |
Division 26: Electrical
| Section | Name |
|---|---|
| 26 05 00 | Common Work Results for Electrical |
| 26 10 00 | Medium-Voltage Electrical Distribution |
| 26 20 00 | Low-Voltage Electrical Distribution |
| 26 24 00 | Switchboards and Panelboards |
| 26 27 00 | Low-Voltage Distribution Equipment |
| 26 50 00 | Lighting |
| 26 51 00 | Interior Lighting |
| 26 56 00 | Exterior Lighting |
Three-Part Specifications
Within each MasterFormat section, specifications follow a standardized three-part format:
| Part | Name | Contents |
|---|---|---|
| Part 1 | General | Related sections, submittals, quality assurance, referenced standards (ASTM, UL, etc.) |
| Part 2 | Product | Materials, manufacturing requirements, quality grades, finishes |
| Part 3 | Execution | Installation requirements, construction methods, workmanship standards |
Reading Spec References
When someone references "03 31 00, 1.05, A" they mean:
- 03 31 00 = Structural Concrete (the MasterFormat section)
- 1.05 = Section 1.05 within Part 1 (often Quality Assurance)
- A = Subsection A within that section
How MasterFormat Is Used
Beyond organizing specs, MasterFormat is used for:
- Estimating — Cost projections organized by division
- Bid Management — Standardized structure for comparing proposals
- Procurement — Part 2 specs identify exact material requirements
- Budget Tracking — Cost codes aligned to CSI divisions
- Scheduling — Work sequences organized by trade/division
- Facilities Management — O&M manuals organized for quick lookup
- Dispute Resolution — Specs are part of the contract; CSI structure helps identify requirements
Tips for Working with MasterFormat
Reviewing Specs:
- Start with Division 01 for project-wide requirements
- Jump to your trade divisions for technical requirements
- Check Division 00 for bidding and contract conditions
- Cross-reference related divisions (e.g., Div 09 finishes often references Div 26 electrical)
Organizing Your Work:
- Align cost databases to divisions
- Use CSI structure for submittal logs, RFI tracking, and punch lists
- Compare bids using the same division structure
FAQs
What's the difference between CSI and MasterFormat?
CSI (Construction Specifications Institute) is the organization. MasterFormat is their standard for organizing specifications. CSI also publishes SectionFormat and PageFormat.
Do all projects use MasterFormat?
MasterFormat is the dominant standard in North America for commercial construction. Residential projects may use simpler formats. Some government projects layer additional requirements on top.
Where can I get the complete MasterFormat?
The full MasterFormat with all sections and subsections is available for purchase from CSI at csiresources.org. The division-level structure shown in this guide is freely available.
What about divisions 15 and 16?
Before 2004, Division 15 was "Mechanical" and Division 16 was "Electrical." These were redistributed to Divisions 21-28 in the 2004 update. You may still see the old numbering on legacy projects—confirm which version applies.
How does DeadFront use MasterFormat?
DeadFront AI understands MasterFormat structure and uses it to organize spec analysis. When reviewing documents, DeadFront identifies which division requirements deviate from standard practices and flags potential risks by section.
History
- 1963: CSI creates the "Master Specification System" with 16 divisions
- 1975: First official MasterFormat release
- 1978: Joint publication with Construction Specifications Canada (CSC)
- 2004: Major expansion from 16 to 50 divisions
- 2010-2018: Continued updates and revisions
The current officially released version is the 2018 Edition.
Summary
- 50 divisions (00-49) organized into logical subgroups
- Six-digit numbering: Division (XX) → Section (YY) → Subsection (ZZ)
- Divisions 00-14: Procurement, general requirements, and building trades
- Divisions 21-28: Facility services (MEP, fire, security)
- Divisions 31-35: Site and infrastructure
- Divisions 40-48: Process and industrial equipment
Bookmark this page for quick reference when navigating construction specifications.
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Construction Technology
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