| Scs Electrical Enterprises INC | Ronald Douglas Jr Rankin | — | (951) 992 9414 | Electricians | Lakeport · Lake County | — | — |
| Seymour Electric | Ryan James Seymour | — | (707) 479 2480 | Electricians | Hidden Valley Lake · Lake County | — | — |
| Shane Woods Johnson Construction INC | Shane Woods Johnson | — | (209) 603 5388 | GC, remodel, ADU | Cobb · Lake County | — | — |
| Shawna D Smith Construction | Shawna Danielle Smith | — | (209) 781 6625 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Shelden Signs & Lighting | Shelden Signs & Lighting | — | (707) 349 4422 | Other | Lakeport · Lake County | — | — |
| Shields Construction | Eric William Shields | — | (707) 245 6849 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Shocker Electric | Jonathan David Mcaloon | — | (707) 349 1392 | Electricians | Lakeport · Lake County | — | — |
| Shore Side Electric | Jon Jody Shore | — | (707) 279 9248 | Electricians | Kelseyville · Lake County | — | — |
| Skiles & Associates INC | Phillip Andrew Skiles | — | (707) 355 2204 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Skinner Electric | Brandon Scott Skinner | — | (707) 322 7869 | Electricians | Hidden Valley Lake · Lake County | — | — |
| Sm Daly Construction | Sean Michael Daly | — | (415) 559 1187 | GC, remodel, ADU | Hidden Valley Lake · Lake County | — | — |
| Smith Construction & General Engineering INC | Kevin Robert Smith | — | (707) 237 1293 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Solomon Welsh Construction | Solomon Ariel Welsh | solomonwelsh@gmail.com | (916) 583 0744 | GC, remodel, ADU | Cobb · Lake County | — | — |
| Stellar Homebuilding | Stellar Homebuilding | — | (707) 486 0231 | GC, remodel, ADU | Lower Lake · Lake County | — | — |
| Stephen Hebert Painting | Stephen Hebert Painting | — | (707) 987 2674 | Windows, patio, painters | Hidden Valley Lake · Lake County | — | — |
| Sterling Construction | Patrick John Stansberry | — | (707) 337 0874 | GC, remodel, ADU | Nice · Lake County | — | — |
| Steve's Painting | Steve's Painting | steve@stevespainting.com | (707) 489 2000 | Windows, patio, painters | Kelseyville · Lake County | — | — |
| Steven Shafer DBA Shafcon | Steven Shafer DBA Shafcon | — | (707) 262 1800 | Electricians | Lakeport · Lake County | — | — |
| Stevenson Water Treatment & Distribution Systems INC | Richard Charles Stevenson | — | (707) 889 6194 | Other | Middletown · Lake County | — | — |
| Still Water Construction | J Bradford Blair | — | (707) 799 9616 | GC, remodel, ADU | Hidden Valley Lake · Lake County | — | — |
| Strickler Construction And General Engineering | Zach Montana Strickler | — | (707) 889 3264 | Other | Middletown · Lake County | — | — |
| Strongtower Construction | Eryck Adam Lee | — | (707) 850 6459 | GC, remodel, ADU | Clearlake · Lake County | — | — |
| Stultz Construction | Larry Andrew Stultz | — | (707) 263 6855 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Summerfield & Sons Construction | Josh Wesley Summerfield | — | (707) 495 0246 | GC, remodel, ADU | Upper Lake · Lake County | — | — |
| Sumner Construction | Eric Sloan Sumner | — | (707) 998 0221 | GC, remodel, ADU | Clearlake Oaks · Lake County | — | — |
| Superior Garage Door Service | Christopher Darius Jordan | superiordoors707@gmail.com | (707) 263 3455 | Other | Clearlake Oaks · Lake County | — | — |
| T & T Construction | Timothy John Finley | — | (707) 396 3830 | GC, remodel, ADU | Lower Lake · Lake County | — | — |
| T K C Engineering | T K C Engineering | — | (707) 277 7657 | Other | Kelseyville · Lake County | — | — |
| T K Excavation | T K Excavation | — | (707) 489 6056 | Other | Upper Lake · Lake County | — | — |
| The Finishing Touch | The Finishing Touch | — | (707) 326 3378 | Windows, patio, painters | Lakeport · Lake County | — | — |
| The Roof Sharks Escondido | The Roof Sharks Escondido | — | (760) 546-9946 | Other roofers | Escondido · Lake County | — | — |
| Theodore Design & Construction | Edward Elms | — | (415) 385 9735 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Third Generation Plumbing | Third Generation Plumbing | — | (813) 961-8024 | Other | Hidden Valley Lake · Lake County | — | — |
| Thomas A Fryer Repairs And Construction | Thomas Alfred Fryer | — | (707) 245 1510 | GC, remodel, ADU | Upper Lake · Lake County | — | — |
| Tim Agapoff Const | Tim Agapoff Const | — | (707) 217 4331 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Tim Mulder | Tim Mulder | — | (707) 350 2009 | Other | Clearlake Oaks · Lake County | — | — |
| Toluca Lake Pest Control | Toluca Lake Pest Control | — | (747) 380-7044 | Pest, tile roofs | Toluca Lake · Lake County | — | — |
| Tomas Adolfo Barriosgonzalez | Tomas Adolfo Barriosgonzalez | — | (707) 889 4906 | Windows, patio, painters | Clearlake · Lake County | — | — |
| Tony Bordessa Construction | Tony Ezio Sr Bordessa | — | (707) 350 9675 | GC, remodel, ADU | Clearlake · Lake County | — | — |
| Torrent Plumbing | Torrent Plumbing | — | (707) 355 1000 | Other | Middletown · Lake County | — | — |