| Gunnarsson Construction INC | Gregory Lee Erlendson | pipinita21@hotmail.com | (707) 263 0382 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Gutter Masters | Gerald Duane Greenwood | %20bob@guttermasters.com | (707) 279 1524 | Other | Kelseyville · Lake County | — | — |
| Gvm Construction | Vergaramacias Gustavo | — | (916) 370 8948 | GC, remodel, ADU | Hidden Valley Lake · Lake County | — | — |
| H D Excavating | Travis William Harborth | — | (707) 350 3815 | Other | Lower Lake · Lake County | — | — |
| Habitat For Humanity Lake County Ca INC | Stephen James Schwartz | — | (707) 994 1100 | GC, remodel, ADU | Lower Lake · Lake County | — | — |
| Hanson Plumbing | Hanson Plumbing | hansonplumbingindustries@gmail.com | (612) 757-3342 | Other | Lakeport · Lake County | — | — |
| Harmony Air INC | Shempliner Alexander | — | (707) 239 9288 | HVAC | Kelseyville · Lake County | — | — |
| Heartwood Builders | Heartwood Builders | — | (707) 272 5373 | GC, remodel, ADU | Clearlake Park · Lake County | — | — |
| Hedge Refrigeration Service | David Samuel Hedge | — | (707) 809 7424 | HVAC | Hidden Valley Lake · Lake County | — | — |
| Heirloom Hardwood Floors | Heirloom Hardwood Floors | — | (707) 228 8521 | Other | Nice · Lake County | — | — |
| Henry Repairs HVAC INC | Charles Allen Tanti | — | (707) 263 6598 | HVAC | Lakeport · Lake County | — | — |
| Hiatt Construction | Aaron Richard Hiatt | — | (707) 245 6860 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| High Valley Ridge Ranch | High Valley Ridge Ranch | — | (707) 349 2582 | Other | Glenhaven · Lake County | — | — |
| High Valley Tile & Stone | High Valley Tile & Stone | — | (707) 350 1526 | Other | Clearlake Oaks · Lake County | — | — |
| Hill Floor Service | Jason Theon Hill | — | (707) 953 7825 | Other | Clearlake Oaks · Lake County | — | — |
| Hill Side Steel | Hill Side Steel | hillsidesteel@gmail.com | (707) 393 1658 | Other | Clearlake Oaks · Lake County | — | — |
| Home Within A Home Construction | Sheral Ann Brekke | — | (707) 295 7116 | GC, remodel, ADU | Hidden Valley Lake · Lake County | — | — |
| Homesmart Services | Louis Lee Jr Brasher | — | (707) 533 5210 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Hommer And Son's Construction | Mark Anthony Hommer | — | (707) 349 9272 | GC, remodel, ADU | Kelseyville · Lake County | — | — |
| Hopkins Construction | Mark Jeremy Hopkins | info@hopkinsconstruction.com | (707) 263 0800 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Howard Seal & Stripe | Howard Seal & Stripe | — | (530) 332 0746 | Other | Kelseyville · Lake County | — | — |
| Hoy Construction | Eric Ronald Lewis Hoy | — | (707) 472 8391 | GC, remodel, ADU | Nice · Lake County | — | — |
| Hulsey Construction | Jackie Monroe Hulsey | — | (707) 272 5749 | GC, remodel, ADU | Nice · Lake County | — | — |
| Humberto's Roofing | Humberto Negrete | — | (707) 994 7643 | Other roofers | Lower Lake · Lake County | — | — |
| Hurtado's Roofing | Hurtado Garcia Jose Raul | — | (971) 268 4716 | Other roofers | Clearlake Oaks · Lake County | — | — |
| Hutchison Electrical | Claud Stanley Ty Hutchison | hutchelect76@gmail.com | (707) 530 4397 | Electricians | Middletown · Lake County | — | — |
| Hutton Well Drilling | Hutton Well Drilling | — | (707) 349 1191 | Other | Upper Lake · Lake County | — | — |
| I H S Construction INC | James Brian Hoyt | — | (707) 695 0745 | GC, remodel, ADU | Clearlake · Lake County | — | — |
| Icaria Development | Icaria Development | — | (707) 894 3205 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Imagine It Construction | Farren Cleve Crabtree | — | (925) 580 4620 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Impact Welding & Fabrication INC | Angel Elias Jimenez | — | (707) 262 2230 | Other | Kelseyville · Lake County | — | — |
| In Sink | In Sink | — | (707) 738 7880 | Other | Hidden Valley Lake · Lake County | — | — |
| Inland Empire General Contractors INC | Inland Empire General Contractors INC | — | (951) 581-5851 | GC, remodel, ADU | Lake Elsinore · Lake County | — | — |
| Innovative Builders | Innovative Builders | — | (707) 484 4651 | GC, remodel, ADU | Cobb · Lake County | — | — |
| Integrated Electrical Services | Kenneth Alan Harper | — | (707) 621 0523 | Electricians | Kelseyville · Lake County | — | — |
| Ipc Renovations | Kenneth Glenn Williams | — | (707) 235 2395 | GC, remodel, ADU | Middletown · Lake County | — | — |
| Irish Tile & Stone | Irish Tile & Stone | — | (707) 484 9150 | Other | Hidden Valley Lake · Lake County | — | — |
| Iron Horse Builders | Iron Horse Builders | — | (707) 975 3981 | GC, remodel, ADU | Lakeport · Lake County | — | — |
| Isaiah's Plumbing | Isaiah's Plumbing | — | (707) 391 7824 | Other | Upper Lake · Lake County | — | — |
| J C Builders | J C Builders | — | (707) 489 7990 | GC, remodel, ADU | Kelseyville · Lake County | — | — |