C-51 Structural Steel Contractor license in California

Updated November 1, 2026 · Official name from CSLB's classification list

• 1,583licenses hold C-51
• 95.1%Clear (CA addresses)
• 28.3%workers' comp exempt (all: 49.6%)
• 99.9%contractor's bond on file
• 15.3 yrsmedian time licensed
• 73.5%businesses, not sole owners

C-51 contractors fabricate and erect structural steel shapes and plates used as structural members in buildings and other structures. The rigging, riveting, welding and metal roofing that go with that work are included.

In a house, a C-51 might set a steel beam when a wall is opened up, or a steel moment frame for seismic strength. Most of the trade is commercial, industrial and multistory work.

Typical work under C-51

• Steel beams and columns
• Steel moment frames
• Steel stairs and platforms that are structural
• Rigging and erecting steel members
• Field welding and bolting of structural steel

Work that needs a different license

• Rebar inside concrete: C-50 Reinforcing Steel
• Decorative railings and gates: C-23 Ornamental Metal
• Repair welding with no steel erection: C-60 Welding

Tips before hiring

• Ask for the engineer's drawings the steel is based on, and confirm the steel matches them.
• Ask whether field welds need special inspection and who pays for it.
• For a beam in a house, ask how the load will be shored while the wall comes out.
• Ask how the steel will be protected from rust, especially where it is exposed outside.

Where C-51 contractors are

The cities with the most C-51 license holders in CSLB's current file:

1. Structural Steel Contractors in Los Angeles: 43
2. Structural Steel Contractors in Bakersfield: 41
3. Structural Steel Contractors in San Francisco: 32
4. Structural Steel Contractors in San Diego: 24
5. Structural Steel Contractors in Anaheim: 21
6. Structural Steel Contractors in Riverside: 21
7. Structural Steel Contractors in Corona: 20
8. Sacramento: 18
9. Fresno: 17
10. Santa Ana: 16

All structural steel contractors lists

Cities with at least 20 C-51 license holders, largest first:

• Los Angeles (43)
• Bakersfield (41)
• San Francisco (32)
• San Diego (24)
• Anaheim (21)
• Riverside (21)
• Corona (20)

How to verify a C-51 license

1. Search the business or license number here and confirm C-51 is listed on the profile.
2. Check the same number on CSLB's Instant License Check.
3. Read our full guide to checking a contractor license.

Related license types

• C-50 Reinforcing Steel Contractor
• C-60 Welding Contractor
• C-23 Ornamental Metal Contractor
• B General Building Contractor

Source: CSLB public data · Updated November 1, 2026 Status can change at any time. Verify on CSLB's Instant License Check.

More license types: ← C-50 Reinforcing Steel Contractor · C-53 Swimming Pool Contractor →