| J P A General Contractor | J P A General Contractor | — | (925) 577 5752 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| J P Aspatore Painting And Drywall | Joseph Peter Aspatore | — | (925) 946 1436 | Windows, patio, painters | Walnut Creek · Contra Costa County | — | — |
| J P H Construction | Joseph Patrick Hopkins | — | (925) 207 6886 | Electricians | Concord · Contra Costa County | — | — |
| J P O Construction | Justin Alan Posey | — | (925) 250 4604 | Other | Discovery Bay · Contra Costa County | — | — |
| J Q Construction | Quezada Juanluis | — | (925) 421 4354 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| J R Construction | Jose Luis Ramirez | — | (925) 980 3748 | GC, remodel, ADU | Antioch · Contra Costa County | — | — |
| J R Flooring Services INC | Garcia Peraza Juan | — | (925) 427 5239 | Other | Pittsburg · Contra Costa County | — | — |
| J R Lucas Painting / Cal-com | John Robert Lucas | — | (925) 584 0577 | Windows, patio, painters | Brentwood · Contra Costa County | — | — |
| J R Painting INC | Ramirez Pelestor Juan | — | (925) 325 3973 | Windows, patio, painters | Antioch · Contra Costa County | — | — |
| J R W Construction INC | Kevin William Wood | — | (925) 831 1615 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| J R W Painting | J R W Painting | — | (925) 984 4149 | Windows, patio, painters | Danville · Contra Costa County | — | — |
| J S Builders LLC | Joseph Stephen Stamates | — | (925) 399 8811 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| J S Electric | Jim Leon Smith | — | (925) 939 5220 | Electricians | Martinez · Contra Costa County | — | — |
| J S Kendall Construction INC | Jeffrey Scott Kendall | — | (925) 946 9294 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| J S Plumbing | J S Plumbing | — | (925) 687 9701 | Other | Concord · Contra Costa County | — | — |
| J Schwab Construction | Jeffrey Thomas Schwab | — | (415) 240 7753 | GC, remodel, ADU | Bethel Island · Contra Costa County | — | — |
| J Snow Shutter Installation | J Snow Shutter Installation | — | (510) 755 2867 | Other | Pinole · Contra Costa County | — | — |
| J T Gaddis Heating & Air | Jeffrey Todd Gaddis | — | (925) 580 5817 | HVAC | Discovery Bay · Contra Costa County | — | — |
| J Tragarz Construction | Joshua Thomas Tragarz | — | (916) 747 8036 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| J Tyler Builders | J Tyler Builders | — | (510) 672 4031 | GC, remodel, ADU | Kensington · Contra Costa County | — | — |
| J V General Construction | Vargas Jesus | — | (925) 381 3668 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| J V Lucas Paving INC | James Vernon Lucas | — | (925) 283 8027 | Other | Martinez · Contra Costa County | — | — |
| J V Telecom | J V Telecom | — | (925) 580 8392 | Other | Concord · Contra Costa County | — | — |
| J Veltkamp Builders INC | Jeremy Dean Veltkamp | — | (925) 360 4461 | GC, remodel, ADU | Danville · Contra Costa County | — | — |
| J W Enterprises | John William Jr Edley | info@jwenterprises.com | (916) 417 8079 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| J W Hardwood Floors Etc | J W Hardwood Floors Etc | — | (925) 787 7761 | Other | Brentwood · Contra Costa County | — | — |
| J W Mc Caa Construction | James Walter Mc Caa | — | (925) 360 3545 | GC, remodel, ADU | Clayton · Contra Costa County | — | — |
| J Watkins Construction | John Clarence Watkins | — | (350) 217 0876 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| J Wooll Electric DBA Voltman | Jeffery Michael Wooll | — | (925) 395 3146 | Electricians | Martinez · Contra Costa County | — | — |
| J&a Bay Builders INC | Juan Francisco Regalado Padilla | — | (650) 561 2353 | GC, remodel, ADU | Discovery Bay · Contra Costa County | — | — |
| J&i Demolition INC DBA J&i Construction | Gregory Mark Robillard | — | (510) 691 6968 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| J&j Dynamic Construction INC | Michael Jason Sterlino | — | (510) 206 2625 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| J&m Contra Costa Rooter Plumbing LLC | Miguel De Jesus Serrano Garcia | — | (925) 214 1057 | Other | Concord · Contra Costa County | — | — |
| J's Modern Landscaping INC | Francisco Javier Barajas | — | (925) 451 8400 | Windows, patio, painters | Brentwood · Contra Costa County | — | — |
| J's Plumbing | J's Plumbing | — | (925) 339 3144 | Other | Martinez · Contra Costa County | — | — |
| J. George Construction | George Juan | jgconstructionllc2024@gmail.com | (925) 446 9291 | GC, remodel, ADU | Oakley · Contra Costa County | — | — |
| J. Solano Construction | Jose Antonio Solano Ramirez | — | (510) 830 5308 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| J.clucas Construction | Joseph Konrad Clucas | — | (510) 847 4878 | GC, remodel, ADU | Richmond · Contra Costa County | — | — |
| J5 Homes Construction | Jamshidnejad Ava | — | (510) 853 4459 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| J_allan Chausse Painting | J_allan Chausse Painting | — | (650) 400 4885 | Windows, patio, painters | Concord · Contra Costa County | — | — |