| Bifulco Builders INC | Todd Cliff Bifulco | — | (925) 451 7748 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| Big Blue Construction | Valdez Roberto | — | (510) 910 9379 | GC, remodel, ADU | El Cerrito · Contra Costa County | — | — |
| Big Chief Tree Service Incorporated | Peter Kent Rudy | — | (510) 528 3588 | Tree | El Cerrito · Contra Costa County | — | — |
| Big D's Garage Doors LLC | Sheff Duane | — | (925) 383 8337 | Other | Antioch · Contra Costa County | — | — |
| Big Dreams Construction | Iram Santiago Martinez | — | (925) 848 8599 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Big Hammer Construction | Joseph William Recht | — | (510) 867 5573 | GC, remodel, ADU | Kensington · Contra Costa County | — | — |
| Big League Builder | Big League Builder | — | (925) 337 0547 | GC, remodel, ADU | Discovery Bay · Contra Costa County | — | — |
| Big Mac Construction | Tyler Lynn Douglass | — | (925) 383 3365 | Electricians | Lafayette · Contra Costa County | — | — |
| Big Pipe Mechanical | Big Pipe Mechanical | — | (415) 767 6008 | HVAC | Brentwood · Contra Costa County | — | — |
| Big Sky Welding | Big Sky Welding | — | (925) 765 7383 | Other | Concord · Contra Costa County | — | — |
| Big Valley Pipelines | Sean Thomas Holmes | — | (925) 839 3666 | Other | Clayton · Contra Costa County | — | — |
| Bigo Construction INC | Jose Fernando Ortega Vega | — | (925) 383 1142 | GC, remodel, ADU | Pittsburg · Contra Costa County | — | — |
| Bilan Construction | Bilic Safet | info@bilanconstruction.com | (310) 377-0555 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| Bill Du Moulin General Contractor | Bill Du Moulin General Contractor | — | (510) 847 9508 | GC, remodel, ADU | Point Richmond · Contra Costa County | — | — |
| Bill Nobriga | Bill Nobriga | — | (925) 216 8071 | Other | Antioch · Contra Costa County | — | — |
| Bill Schwarck Electric | William Frederick Schwarck | — | (510) 207 8185 | Electricians | Walnut Creek · Contra Costa County | — | — |
| Bill Younger Construction | William Allan Younger | — | (925) 285 7961 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Bill's Heating & Cooling | Bill's Heating & Cooling | — | (805) 608 9328 | HVAC | Oakley · Contra Costa County | — | — |
| Bill's Welding | Bill's Welding | — | (510) 915 8448 | Other | Richmond · Contra Costa County | — | — |
| Billett Electric LLC | Joshua James Alexan Billett | — | (623) 800 1883 | Electricians | Brentwood · Contra Costa County | — | — |
| Bird Electric INC | Samuel Kyle Bird | — | (415) 963 4407 | Electricians | Brentwood · Contra Costa County | — | — |
| Bl Pavers INC | Bruno De Lima Sr Pereira | — | (925) 272 5250 | Pool | Danville · Contra Costa County | — | — |
| Blaces Grout Restoration | Blaces Grout Restoration | — | (925) 683 0141 | Restoration | Walnut Creek · Contra Costa County | — | — |
| Black Diamond Custom Landscape | Carlos Fernando Azurdia Herrera | — | (415) 568 5327 | Windows, patio, painters | Richmond · Contra Costa County | — | — |
| Black Diamond Glass | Brian Bud Birdsell | — | (925) 267 3067 | Windows, patio, painters | Pittsburg · Contra Costa County | — | — |
| Black Diamond Paint And Wallcovering | Black Diamond Paint And Wallcovering | — | (925) 719 5792 | Windows, patio, painters | Oakley · Contra Costa County | — | — |
| Black Diamond Painting | Black Diamond Painting | — | (415) 713 6582 | Windows, patio, painters | Concord · Contra Costa County | — | — |
| Black Diamond Residential Remodeling INC | Ramon Alejandro Lopez Ceja | — | (925) 577 6802 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Black Diamond Roofing INC | Diaz Esaul | — | (510) 775 5290 | Other roofers | Concord · Contra Costa County | — | — |
| Black Oak Construction | Michael A J Bullis | — | (925) 788 7194 | GC, remodel, ADU | Clayton · Contra Costa County | — | — |
| Blackhawk Pool Care & Repairs | Joe Adam Yncio Anton | — | (925) 255 0020 | Pool | Danville · Contra Costa County | — | — |
| Blacks Electrical | Lamont Lovell Black | — | (510) 239 6307 | Electricians | Antioch · Contra Costa County | — | — |
| Blackstock Construction | Nathan Coredon Blackstock | — | (541) 891 4303 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Blackstone Global | David Joseph Tognela | — | (925) 718 3126 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Blackstone Surfaces Jv | Custom Construction Walsh | — | (925) 421 9712 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Blank Canvas Painting INC | Sergio Emmanuel Lopez-Poblano | — | (415) 316 3398 | Windows, patio, painters | Pittsburg · Contra Costa County | — | — |
| Blazing Improvements | Blazing Improvements | — | (925) 899 3095 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Blockchain Construction Corporation | Jesse James Markham | — | (510) 672 7729 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| Blodgett's Abbey Carpet & Flooring | Karen Letitia Blodgett | — | (925) 284 4807 | Other | Lafayette · Contra Costa County | — | — |
| Blodgett's Home Improvement INC | Michael William| Blodgett Mick William Blodgett | — | (925) 683 5946 | GC, remodel, ADU | Danville · Contra Costa County | — | — |