| 3dl Forever Flooring INC | De Leon Daniel Diaz | — | (619) 292 5570 | Other | Spring Valley · San Diego County | — | — |
| 3G Engineering Corp | Jose Adolfo Gastelo Pimentel | — | (619) 495 6442 | Other | Spring Valley · San Diego County | — | — |
| 3js Construction INC | Jose D Jacobo | buildzoomsupport@blockrenovation.com | (858) 688 8247 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 3p's Home Improvement INC | Pedro Gabriel Maldonado Santiago | — | (760) 717 6230 | GC, remodel, ADU | Oceanside · San Diego County | — | — |
| 3sixty Innovation INC | Mohamad Ismieal Muhsin | — | (858) 304 1093 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 4 Brothers Drywall INC | Candelario Larios | — | (619) 642 1941 | Other | Ramona · San Diego County | — | — |
| 4 J Construction | Jesse Derwin Simeroth | — | (760) 533 0586 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 4 Jay's Construction Services INC | Jesus Andres Ordaz Estala | — | (619) 576 1279 | GC, remodel, ADU | El Cajon · San Diego County | — | — |
| 4 M Mechanical INC | Michael Anthony Foutch | — | (619) 944 4822 | HVAC | San Diego · San Diego County | — | — |
| 4 U 2 Idol Landscape | 4 U 2 Idol Landscape | — | (619) 807 6516 | Windows, patio, painters | San Diego · San Diego County | — | — |
| 4 U S Renovation INC | Marshall Henry Dohoney | — | (858) 643 9088 | Other roofers | San Diego · San Diego County | — | — |
| 4 Way Pool Excavation INC | Alvarez Benjamin Ledezma | — | (760) 975 6334 | Pool | Escondido · San Diego County | — | — |
| 4 X 8 Construction INC | Vincent Joseph Posada | — | (619) 279 2941 | GC, remodel, ADU | Poway · San Diego County | — | — |
| 481 Plumb | 481 Plumb | — | (858) 342 5796 | Other | Del Mar · San Diego County | — | — |
| 49 Plumbing | 49 Plumbing | — | (916) 825 5230 | Other | La Jolla · San Diego County | — | — |
| 4B Electric INC | Michael Robert Barnett | — | (619) 723 0209 | Electricians | El Cajon · San Diego County | — | — |
| 4d&n Landscaping INC | Daniel Alberto Flores Medina | — | (619) 410 2052 | Windows, patio, painters | Chula Vista · San Diego County | — | — |
| 4dream Builders INC | Alfonso Sr Mendez | aqremodeling2@gmail.com | (619) 416 4430 | GC, remodel, ADU | Chula Vista · San Diego County | — | — |
| 4G Grading | Gregory Douglas Garner | — | (760) 522 8920 | Other | Ramona · San Diego County | — | — |
| 4liberty INC | Srpouhi L Galpchian | — | (619) 559 1913 | Other | Encinitas · San Diego County | — | — |
| 4mar Construction INC | Marco Tulio Ramos Segura | guy@infinitydesignbuild.com | (619) 955 3207 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 4sides Painting INC | Asadullah Khani | — | (619) 538 5874 | Windows, patio, painters | San Diego · San Diego County | — | — |
| 4th Dimension Drywall | 4th Dimension Drywall | — | (858) 568 3337 | Other | El Cajon · San Diego County | — | — |
| 5 In 1 Construction INC | Victor Manuel Carrasco | guy@infinitydesignbuild.com | (619) 874 0406 | GC, remodel, ADU | San Ysidro · San Diego County | — | — |
| 5 North Media | Robert Thomas Jr Bobuk | — | (858) 621 2155 | Other | San Diego · San Diego County | — | — |
| 5 Olague Construction INC | Marco Antonio Olague-Rivera | — | (619) 372 3105 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 5 S Contracting INC DBA Landmark Mechanical | Gary Ray Seelinger | — | (858) 279 1222 | HVAC | San Diego · San Diego County | — | — |
| 5 Star Mechanical INC | Aleksei Geringer | — | (619) 766 5520 | HVAC | San Diego · San Diego County | — | — |
| 5-18 Synthetic Products | Ezequiel Resendiz | — | (760) 594 4301 | Other | Vista · San Diego County | — | — |
| 517 Electric | Brandon Lee Swart | — | (909) 289 8619 | Electricians | Fallbrook · San Diego County | — | — |
| 555 Construction | Mushtaq Mohsen Nasse Alshimery | — | (619) 844 3170 | Electricians | San Diego · San Diego County | — | — |
| 568 Construction INC | Daniel So | — | (619) 995 4172 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 5thcsi | Linda Posada Rivera | lindarivera@5thcsi.com | (619) 651 5110 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 5trades INC DBA 5trades Construction | Ramsey Emad Khedr | ramsey@5tradesconstruction.com | (619) 909 4242 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 6 Stars Engineering | 6 Stars Engineering | — | (760) 755 4951 | Windows, patio, painters | Lakeside · San Diego County | — | — |
| 6-2 Plumbing INC | Sixto Pablo Velazquez | — | (619) 894 3721 | Other | El Cajon · San Diego County | — | — |
| 619 Construction | Johann Lester Hernandez Oblitas | — | (323) 794 4361 | GC, remodel, ADU | San Diego · San Diego County | — | — |
| 619 Electric | Mitchell Clark Vansant | — | (805) 444 5758 | Electricians | San Diego · San Diego County | — | — |
| 619 Heating And Air | 619 Heating And Air | — | (619) 616 5538 | HVAC | Chula Vista · San Diego County | — | — |
| 619 Painting | 619 Painting | — | (619) 992 5696 | Windows, patio, painters | Spring Valley · San Diego County | — | — |