| Irwin Excavating Services INC | Jesse Leroy Irwin | — | (707) 478 8505 | Other | Windsor · Sonoma County | — | — |
| Irwin Well Drilling INC | Nolan James Irvine | irwinwelldrilling@gmail.com | (707) 303 5984 | Other | Fulton · Sonoma County | — | — |
| Isaac Garcia Construction | Isaac Diaz Garcia | — | (707) 486 7666 | GC, remodel, ADU | Sebastopol · Sonoma County | — | — |
| Isetta Data & Communications INC | Andrew John Isetta | — | (707) 888 1102 | Other | Cotati · Sonoma County | — | — |
| Italtile Stone | Italtile Stone | — | (707) 363 5990 | Other | Sonoma · Sonoma County | — | — |
| J & A Electric INC | Jorge Alcazar | — | (707) 800 2569 | Electricians | Petaluma · Sonoma County | — | — |
| J & A Stone And Tile INC | Alexander Blair | — | (505) 699 1298 | Other | Sebastopol · Sonoma County | — | — |
| J & B Const Co | Joseph Eugene Barkela | — | (707) 291 2222 | GC, remodel, ADU | Santa Rosa · Sonoma County | — | — |
| J & D Restaurant Maintenance | J & D Restaurant Maintenance | — | (415) 793 5726 | Other | Petaluma · Sonoma County | — | — |
| J & J Custom Builders INC | Jeffrey William O'hanlon | — | (707) 480 2790 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| J & J Electric | Jason Weatherby Jackson | — | (707) 800 3884 | Electricians | Sebastopol · Sonoma County | — | — |
| J & L Signs | J & L Signs | — | (707) 953 4874 | Other | Santa Rosa · Sonoma County | — | — |
| J & M Drywall | J & M Drywall | — | (415) 847 0476 | Windows, patio, painters | Petaluma · Sonoma County | — | — |
| J & N Construction | James Peter Tierney | — | (415) 302 5235 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| J A Floor Covering | J A Floor Covering | — | (707) 332 9576 | Other | Sebastopol · Sonoma County | — | — |
| J A M Precision Flooring INC | Jose Antonio Martinez Garibay | — | (510) 329 8522 | Other | Graton · Sonoma County | — | — |
| J A Mejia Construction INC | Juan Antonio Mejia Medina | — | (707) 807 1320 | GC, remodel, ADU | Rohnert Park · Sonoma County | — | — |
| J A O'donnell Construction | Jason Atlantis O'donnell | — | (707) 322 2711 | GC, remodel, ADU | Jenner · Sonoma County | — | — |
| J A Serrano Construction | Jose Alfredo Serrano Huitron | — | (707) 332 3987 | GC, remodel, ADU | Rohnert Park · Sonoma County | — | — |
| J And C Painting And Staining INC | Carlos Francisco Chan Novelo | — | (707) 703 3385 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| J And M Building Specialties INC | Julianne Heliotes | — | (707) 762 4109 | Other | Petaluma · Sonoma County | — | — |
| J B Drywall | J B Drywall | — | (707) 292 4629 | Other | Petaluma · Sonoma County | — | — |
| J B Hernandez Painting | J B Hernandez Painting | — | (415) 425 8540 | Windows, patio, painters | Rohnert Park · Sonoma County | — | — |
| J B Landscapes | J B Landscapes | — | (707) 974 7157 | Windows, patio, painters | Rohnert Park · Sonoma County | — | — |
| J B Lind Plumbing Company | James Daniel Lind | robert@jblindplumbing.com | (208) 408 9280 | Other | Glen Ellen · Sonoma County | — | — |
| J B Mechanical | J B Mechanical | — | (707) 799 0206 | Other | Cotati · Sonoma County | — | — |
| J B Painting | J B Painting | — | (707) 569 6074 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| J B Tile & Marble | J B Tile & Marble | — | (707) 481 0517 | Other | Petaluma · Sonoma County | — | — |
| J Bradford Construction | Jeffery Bradford Cisi | — | (415) 686 7729 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| J C 2 Enterprise | J C 2 Enterprise | — | (707) 326 6442 | Windows, patio, painters | Santa Rosa · Sonoma County | — | — |
| J C C A | J C C A | — | (760) 213 8889 | GC, remodel, ADU | Sonoma · Sonoma County | — | — |
| J C C General Construction | Jaime Castaneda Cordova | — | (707) 889 4694 | GC, remodel, ADU | Sonoma · Sonoma County | — | — |
| J C Electric | John Joseph Cavanaugh | — | (707) 342 7153 | Electricians | Windsor · Sonoma County | — | — |
| J C General Engineering Contractor INC | Jose Antonio Franco Chavez | — | (707) 241 5193 | Other | Petaluma · Sonoma County | — | — |
| J Clark Heating & Cooling | J Clark Heating & Cooling | — | (707) 501 0657 | HVAC | Sonoma · Sonoma County | — | — |
| J Cueva Construction | Jesus Adan Ruelas Cueva | — | (707) 637 3086 | GC, remodel, ADU | Sonoma · Sonoma County | — | — |
| J D Fowler Construction | Jeffrey Duncan Fowler | — | (707) 228 2411 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |
| J D Jones Construction INC | Jason Dion Jones | — | (707) 543 6529 | Other | Santa Rosa · Sonoma County | — | — |
| J D Luiz Electric INC | Jason Dominic Luiz | — | (707) 364 4599 | Electricians | Petaluma · Sonoma County | — | — |
| J D Minick Construction | Jefferey Dennis Minick | — | (707) 658 1505 | GC, remodel, ADU | Petaluma · Sonoma County | — | — |