CSI MasterFormat divides every construction project into 49 numbered divisions, organized from general requirements through specialty equipment and systems. Every cost estimate, spec book, and bid form in US commercial construction is structured around these divisions, which is why understanding them is essential for anyone reading a project manual or assembling a bid.
What Is CSI MasterFormat?
MasterFormat is the standard numbering and titling system published by the Construction Specifications Institute (CSI), used to organize project specifications, cost estimates, and bid documents across the US construction industry. Instead of trades being listed in random order, every project manual and estimate follows the same numbered structure — so a Division 09 reference always means finishes, and Division 26 always means electrical, no matter which project you’re looking at. This consistency is what lets a GC, a subcontractor, an estimator, and an owner all read the same set of specifications and immediately know where to find the section relevant to their trade.
All 49 CSI MasterFormat Divisions
CSI MasterFormat groups its 49 divisions into 5 broad ranges. Each range below covers a related set of trades and systems.
1. Divisions 00–09 — Procurement, General Requirements, Facility Construction
| Div | Title | What It Covers |
| 00 | Procurement and Contracting Requirements | Bid forms, contract conditions, instructions to bidders |
| 01 | General Requirements | Project administration, quality requirements, temporary facilities |
| 02 | Existing Conditions | Demolition, hazardous material remediation, site survey |
| 03 | Concrete | Formwork, reinforcement, cast-in-place and precast concrete |
| 04 | Masonry | CMU, brick veneer, stone, mortar and masonry accessories |
| 05 | Metals | Structural steel, metal fabrications, decking |
| 06 | Wood, Plastics, and Composites | Rough carpentry, millwork, architectural woodwork |
| 07 | Thermal and Moisture Protection | Waterproofing, insulation, roofing membranes, firestopping |
| 08 | Openings | Doors, windows, glazing, hardware |
| 09 | Finishes | Drywall, flooring, painting, ceilings |
2. Divisions 10–14 — Specialties, Equipment, Furnishings
| Div | Title | What It Covers |
| 10 | Specialties | Signage, toilet partitions, fire extinguisher cabinets |
| 11 | Equipment | Food service, laboratory, and other fixed equipment |
| 12 | Furnishings | Casework, window treatments, furniture |
| 13 | Special Construction | Pre-engineered structures, pools, special-purpose rooms |
| 14 | Conveying Equipment | Elevators, escalators, lifts |
3. Divisions 21–28 — Fire Suppression, Plumbing, HVAC, Electronics
| Div | Title | What It Covers |
| 21 | Fire Suppression | Sprinkler systems, standpipes, fire pumps |
| 22 | Plumbing | Domestic water, sanitary waste, plumbing fixtures |
| 23 | HVAC | Ductwork, equipment, controls |
| 25 | Integrated Automation | Building automation system integration |
| 26 | Electrical | Wiring, panels, switchgear, lighting |
| 27 | Communications | Structured cabling, data, telecom |
| 28 | Electronic Safety and Security | Fire alarm, access control, CCTV |
4. Divisions 31–35 — Earthwork and Exterior Improvements
| Div | Title | What It Covers |
| 31 | Earthwork | Grading, excavation, soil stabilization |
| 32 | Exterior Improvements | Paving, landscaping, fencing |
| 33 | Utilities | Water, sewer, storm drainage, gas distribution |
| 34 | Transportation | Roadways, bridges, rail |
| 35 | Waterway and Marine Construction | Docks, marine structures, dredging |
5. Divisions 40–49 — Process Equipment and Specialty Systems
| Div | Title | What It Covers |
| 40 | Process Interconnections | Process piping between systems |
| 41 | Material Processing and Handling Equipment | Conveyors, bulk material handling |
| 43 | Process Gas and Liquid Handling | Storage tanks, process piping systems |
| 44 | Pollution and Waste Control Equipment | Treatment systems, emissions control |
| 46 | Water and Wastewater Equipment | Treatment plant equipment |
| 48 | Electrical Power Generation | Generators, solar, renewable energy systems |
Note: Some division numbers (15, 16, 17, 19, 20, 24, 29, 30, 36-39, 42, 45, 47, 49) are reserved or rarely used in current practice, older editions of MasterFormat used different numbering for trades like plumbing (15) and electrical (16) that have since moved to Divisions 22 and 26.
Why CSI Divisions Matter for Your Estimate
Every line item in a properly organized construction estimate should map to a specific CSI division. This isn’t just bureaucratic structure, it’s what makes an estimate usable. A GC assembling a bid needs to quickly see total cost by division to compare against budget, identify which subcontractor packages map to which scope, and confirm nothing has been missed between divisions. When an estimate isn’t organized this way, scope gaps are far more likely, a fireproofing cost (Division 07) accidentally bundled into structural steel (Division 05), or firestopping (also Division 07) left out entirely because it didn’t have an obvious home in a poorly structured estimate. ALM Estimating organizes every estimate by CSI division and sub-section, so it’s immediately usable for bid assembly, GMP development, or sub-bid comparison.
Most Commonly Estimated Divisions
The divisions contractors request estimates for most often: Division 03 — Concrete /concrete-estimating-services/ Division 04 — Masonry /masonry-estimating-services/ Division 07 — Thermal and Moisture Protection /thermal-and-moistures/ Division 09 — Finishes, including drywall /drywall-estimating-services/ and flooring /flooring-estimating-services/ Division 22/23/26 — MEP (mechanical, electrical, plumbing) /mep-estimating-service/ Division 26 — Electrical specifically /electrical-estimating-services/ Division 31-33 — Sitework /sitework-estimating-services/.
Get a CSI-Organized Estimate for Your Project
Whether you need a single-division estimate or a full multi-trade takeoff, ALM Estimating organizes every deliverable by CSI MasterFormat division and sub-section, ready to drop directly into your bid assembly. Send us your plans and specifications and get a complete estimate back within 24 hours. Call +1 (917) 718-0084 or visit our contact page to get started.
Frequently Asked Questions
How many CSI MasterFormat divisions are there?
MasterFormat includes 49 numbered divisions, though several numbers are reserved or rarely used in current practice. Most active construction projects use roughly 25-30 divisions depending on project type and complexity.
What division is electrical work under?
Electrical work falls under Division 26. Communications and low-voltage systems are typically Division 27, and electronic safety and security systems (fire alarm, access control) are Division 28.
What’s the difference between Division 22 and Division 23?
Division 22 covers plumbing, domestic water, sanitary waste, and fixtures. Division 23 covers HVAC; heating, ventilation, and air conditioning equipment and ductwork. Both fall under the broader MEP umbrella.
Why do some CSI division numbers skip ahead?
Older editions of MasterFormat assigned numbers differently, for example, plumbing was once Division 15 and electrical was Division 16. The current edition reorganized these into the 20s and added entirely new divisions (40s) for process equipment, which is why some numbers in between are reserved or unused.
