| J C Fence | J C Fence | — | (707) 291 5689 | Other | Middletown · Lake County | — | — |
| J C O Construction | Joshua Caleb O'neal | info@jcoconstruction.com | (707) 355 1231 | GC, remodel, ADU | Lower Lake · Lake County | — | — |
| J D M Construction | Jacob Daniel Mccammon | — | (707) 849 4067 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| J D M Earth Works | J D M Earth Works | — | (707) 245 1669 | Other | Kelseyville · Lake County | — | — |
| J K L Construction & Design INC | Shawn Heber Auten | — | (707) 513 9823 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| J L Services | Jon Howard Lantry | — | (831) 212 6153 | Other | Kelseyville · Lake County | — | — |
| J M Construction | John Sherman Mc Closkey | info@jmconstruction.com | (805) 472-2400 | GC, remodel, ADU | Lucerne · Lake County | — | — |
| J Pantaleon Construction | Jesus Tecpoyot Pantaleon | — | (707) 490 2596 | Other | Finley · Lake County | — | — |
| J T Painting | J T Painting | — | (707) 533 0559 | Windows, patio, painters | Clear Lake · Lake County | — | — |
| J W Electric | Harry Jon Iii Waner | — | (707) 295 6445 | Electricians | Upper Lake · Lake County | — | — |
| J Wood Plumbing | Jacob William Wood | — | (707) 972 3995 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Jaco Heating Air Conditioning & Refrigeration | John Sy Armas | — | (707) 263 3402 | HVAC | Lakeport · Lake County | — | — |
| James Burns Construction | James Arthur Burns | jamesburnsconstruction@gmail.com | (707) 245 0535 | GC, remodel, ADU | Nice · Lake County | — | — |
| James Paul Smith | James Paul Smith | — | (707) 349 3071 | Other | Kelseyville · Lake County | — | — |
| Jan-mar Corporation | Richard Raymond Jr Williams | — | (707) 695 8745 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Jason M Creager | Jason M Creager | — | (707) 355 2550 | GC, remodel, ADU | Lower Lake · Lake County | — | — |
| Jb Electric | Jeffrey Paul Birge | — | (707) 245 0740 | Electricians | Upper Lake · Lake County | — | — |
| Jd Smith Construction Management | Jonathan Daniel Smith | — | (707) 367 6188 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Jdc Industries INC Independent Electrical Company | Jesse Dan Cole | — | (707) 277 0623 | Electricians | Kelseyville · Lake County | — | — |
| Jeri - Co Garage Doors INC | Jon Matthew Woodard | — | (707) 987 9515 | Other | Middletown · Lake County | — | — |
| Jesse Abrao Construction | Jesse Christopher Abrao | — | (707) 350 0151 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Jg Builder | Jg Builder | — | (707) 364 7719 | GC, remodel, ADU | Hidden Valley Lake · Lake County | — | — |
| Jim Salmina | Jim Salmina | — | (707) 350 0277 | Other | Lower Lake · Lake County | — | — |
| Jim's Building Services | James Keith Matejka | — | (650) 867 6968 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Jim's Pumps | Jim's Pumps | — | (707) 394 2277 | Other | Upper Lake · Lake County | — | — |
| Jj Electric Company | John Charles Jr Judson | sales@jj-electric.com | (707) 333 8678 | Electricians | Middletown · Lake County | — | — |
| Jmt Electric INC | Jacob Michael Taylor | — | (707) 495 8138 | Electricians | Middletown · Lake County | — | — |
| Joe Maldonado | Joe Maldonado | — | (415) 609 0209 | Other | Clearlake · Lake County | — | — |
| Joe's Construction Company | Joe's Construction Company | — | (858) 342-6770 | GC, remodel, ADU | Bonsall · Lake County | — | — |
| John Goss Backhoe | John Goss Backhoe | — | (707) 349 1712 | Other | Kelseyville · Lake County | — | — |
| John M Hagan | John M Hagan | — | (707) 263 1151 | HVAC | Lakeport · Lake County | — | — |
| John P Brosnan | John P Brosnan | — | (707) 501 7157 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Jonas Energy Solutions | Edward Allan Kronk | — | (707) 994 5911 | HVAC | Lower Lake · Lake County | — | — |
| Jonathan Mc Queen | Jonathan Mc Queen | — | (707) 272 6314 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Jones Construction | George James Paul Jones | — | (707) 245 1743 | GC, remodel, ADU | Lucerne · Lake County | — | — |
| Jones Real Estate Development LLC | Richard Jay Travis | — | (707) 367 1138 | GC, remodel, ADU | Clearlake Park · Lake County | — | — |
| Jorge A Construction INC | Jorge Junior Arredondo | — | (707) 812 3068 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Jorge L Alvarez Construction | Jorge Luis Alvarez Ruiz | — | (707) 486 2182 | GC, remodel, ADU | Hidden Valley Lake · Lake County | — | — |
| Jose Jaimez DBA Executive Painting | Jose Jaimez DBA Executive Painting | — | (707) 477 5214 | Windows, patio, painters | Loch Lomond · Lake County | — | — |
| Jrr Construction | Joel Reed Radcliff | — | (916) 821 9725 | GC, remodel, ADU | Kelseyville · Lake County | — | — |