| 505 Earthworks LLC | Hayden Kaspar Item | — | (925) 808 5098 | Other | Discovery Bay · Contra Costa County | — | — |
| 506 Bw INC | Guillermo Esau Vallejuarez | — | (562) 760 2090 | GC, remodel, ADU | Los Angeles · Los Angeles County | — | — |
| 509 Builders INC | Brent Oliver Coert | — | (310) 702 5075 | GC, remodel, ADU | Santa Monica · Los Angeles County | — | — |
| 510 Painting & Decorating | 510 Painting & Decorating | — | (510) 292 5093 | Windows, patio, painters | Oakland · Alameda County | — | — |
| 510 Plumbing And Rooter INC | Alan Chavarria | — | (510) 603 4829 | Other | Burbank · Los Angeles County | — | — |
| 517 Electric | Brandon Lee Swart | — | (909) 289 8619 | Electricians | Fallbrook · San Diego County | — | — |
| 525 Automation INC | Nelson Torres | — | (909) 908 2449 | Other | Homeland · Riverside County | — | — |
| 530 Builders | Sam Robert Bueckert | — | (530) 205 8083 | GC, remodel, ADU | Truckee · Nevada County | — | — |
| 530 Pipe Flow | 530 Pipe Flow | info@pipeflow.com | (530) 906 1226 | Other | Auburn · Placer County | — | — |
| 530 Restoration Inc. | 530 Restoration Inc. | admin@airodigital.com | — | Restoration | Paradise · Butte County | — | — |
| 54 Concrete | 54 Concrete | — | (805) 951 9428 | Other | Oxnard · Ventura County | — | — |
| 54 Electric INC | John Robert Brian Pfeiffer | — | (650) 489 5454 | Electricians | Mountain View · Santa Clara County | — | — |
| 548 Group INC | Timothy Perry Free | — | (949) 861 1881 | Other | San Clemente · Orange County | — | — |
| 55 Flooring Tile & Stone Ebrahim Ezzati | Ezzati Ebrahim | — | (714) 300 0700 | GC, remodel, ADU | Anaheim · Orange County | — | — |
| 55 Property Services INC | Roman Henry Nunez | — | (866) 586 2626 | Other roofers | Fullerton · Orange County | — | — |
| 555 Construction | Mushtaq Mohsen Nasse Alshimery | — | (619) 844 3170 | Electricians | San Diego · San Diego County | — | — |
| 559 Construction | Mehdi Mike Pourhabib | — | (559) 696 9106 | GC, remodel, ADU | Fresno · Fresno County | — | — |
| 559 Electric | Nickolas Villegas Solis | — | (559) 731 4436 | Electricians | Visalia · Tulare County | — | — |
| 559 Plumbers LLC | Ryan Lee Valtierra | — | (559) 206 1526 | Other | Madera · Madera County | — | — |
| 559sheds & Fencing | 559sheds & Fencing | — | (559) 916 5457 | GC, remodel, ADU | Fresno · Fresno County | — | — |
| 55geeks | Sahar Maher Osman | — | (855) 554 3357 | Electricians | Martinez · Contra Costa County | — | — |
| 56 West Construction | Harrison Ray Read | — | (503) 800 8467 | GC, remodel, ADU | Ione · Amador County | — | — |
| 562 Construction | Matthew Robert Merz | — | (562) 715 8526 | GC, remodel, ADU | Lakewood · Los Angeles County | — | — |
| 562 Painting Co | Alexander Joshua Carrillo | — | (562) 351 3616 | Windows, patio, painters | Whittier · Los Angeles County | — | — |
| 568 Construction INC | Daniel So | — | (619) 995 4172 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 57 Electric | Mark Anthony Heller | — | (415) 786 4311 | Electricians | Fairfax · Marin County | — | — |
| 57 Heating And Air Conditioning | 57 Heating And Air Conditioning | — | (323) 479 3048 | HVAC | Fullerton · Orange County | — | — |
| 5858 Construction Company | Marcus Marchand Moore | — | (323) 202 0195 | GC, remodel, ADU | Los Angeles · Los Angeles County | — | — |
| 5B Construction | Tung Ba Nguyen | — | (408) 835 5879 | Electricians | San Jose · Santa Clara County | — | — |
| 5B Remodeling Co | Ben Allen Yoder | — | (535) 305 7411 | GC, remodel, ADU | Woodland · Yolo County | — | — |
| 5blox | Eden Rush | — | (323) 621 9368 | GC, remodel, ADU | San Pedro · Los Angeles County | — | — |
| 5D Handyman Service | Daniel Robert Dominguez | — | (559) 321 4721 | GC, remodel, ADU | Fresno · Fresno County | — | — |
| 5G Builder | 5G Builder | — | (562) 233 1111 | GC, remodel, ADU | Costa Mesa · Orange County | — | — |
| 5gold Construction INC | Yuanyuan Xiao Estrada | — | (828) 655 6789 | GC, remodel, ADU | Garden Grove · Orange County | — | — |
| 5J Construction | Jeremy Stephen Ogilby | — | (209) 347 0940 | GC, remodel, ADU | Mariposa · Mariposa County | — | — |
| 5K Builder | 5K Builder | — | (707) 327 7613 | GC, remodel, ADU | Ukiah · Mendocino County | — | — |
| 5P Iron | 5P Iron | — | (916) 293 1130 | Other | Newcastle · Placer County | — | — |
| 5R Construction Company INC | Amarjit Singh Sangha | — | (916) 804 3302 | GC, remodel, ADU | Cameron Park · El Dorado County | — | — |
| 5th Generation Construction | Kenneth Kieth Yablonsky | — | (562) 786 0150 | GC, remodel, ADU | Long Beach · Los Angeles County | — | — |
| 5th Generation Painting | 5th Generation Painting | — | (707) 623 0890 | Windows, patio, painters | Petaluma · Sonoma County | — | — |