| Chris Hertler | Chris Hertler | — | (805) 286 6028 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Chris Lehto Electric | Christopher Harold Lehto | — | (707) 443 3835 | Electricians | Eureka · Humboldt County | — | — |
| Christian & Sons Construction Company | Christian Kyle Gouthier | — | (707) 845 3334 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Christopher Tyler Construction | Christopher Tyler Reynolds | — | (707) 309 3209 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Ciraulo Plumbing Services | Gary James Ciraulo | cirauloplumbing@gmail.com | (707) 497 4213 | Other | Eureka · Humboldt County | — | — |
| Citadel Masonry | Citadel Masonry | — | (707) 267 5836 | Other | Arcata · Humboldt County | — | — |
| Claybons Custom Tile And Design | Claybons Custom Tile And Design | — | (707) 672 4693 | Other | Eureka · Humboldt County | — | — |
| Clean Lines Painting | Clean Lines Painting | — | (707) 407 6420 | Windows, patio, painters | Mc Kinleyville · Humboldt County | — | — |
| Clear Waters Plumbing | Clear Waters Plumbing | clearwatersplumbing@gmail.com | (707) 499 2581 | Other | Eureka · Humboldt County | — | — |
| Clemans Construction Services | Dylan Owen Clemans | — | (707) 599 0829 | GC, remodel, ADU | Arcata · Humboldt County | — | — |
| Cline Plumbing Electric & Construction | Michael Ray Cline | — | (707) 845 5298 | Electricians | Arcata · Humboldt County | — | — |
| Clower Construction | William Lane Anton Clower | — | (707) 496 1890 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Coast To Coast Plumbing | Coast To Coast Plumbing | dispatchexperienceplumbing@gmail.com | (707) 296 6804 | Other | Loleta · Humboldt County | — | — |
| Coastal Construction And Remodeling | Craig Aaron Brown | — | (707) 599 3543 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Coastal Tree Service | Thomas William Head | — | (707) 683 6042 | Tree | Mc Kinleyville · Humboldt County | — | — |
| Coastalco Builders | Nil Shailesh Patel | — | (707) 845 5437 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Coastline Construction | Marc Daniel Schmidt | — | (707) 442 3431 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Colby Company | Ronnie James Colby | — | (530) 412 2617 | GC, remodel, ADU | Arcata · Humboldt County | — | — |
| Colby Construction | Eric Daniel Culbertson | — | (707) 666 5854 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Colin Mac Donald Construction | Colin Thomas Macdonald | — | (707) 599 5113 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Colin Ott Masonry | Colin Ott Masonry | — | (707) 443 4639 | Other | Eureka · Humboldt County | — | — |
| Collings Construction | Jared Wayne Collings | — | (707) 499 5046 | GC, remodel, ADU | Fortuna · Humboldt County | — | — |
| Collins Construction | David Shawn Collins | — | (707) 267 1296 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Collins Sheetmetal | Collins Sheetmetal | — | (408) 781 0806 | Other | Eureka · Humboldt County | — | — |
| Communications Cabling Systems INC | Daniel Robert Browne | dan.browne@communicationscablingsystems.com | (707) 442 2244 | Other | Eureka · Humboldt County | — | — |
| Compass Carpentry INC | Shawn Thomas Herlihy | shawn@compassinspection.services | (707) 499 6381 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Conceptional Electric | Michael Alvin Brown | — | (707) 267 5288 | Electricians | Eureka · Humboldt County | — | — |
| Concrete Pete | Concrete Pete | pete@concretepete.com | (707) 476 9469 | Other | Eureka · Humboldt County | — | — |
| Condit Enterpises | Condit Enterpises | — | (707) 499 8749 | GC, remodel, ADU | Cutten · Humboldt County | — | — |
| Constructive Design's INC | Christopher James Hanly | — | (707) 834 2355 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Contour Construction | Gregory John Burger | — | (780) 723-5051 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Cooke Lighting / Electric | Jeffrey Wade Cooke | — | (707) 839 9304 | Electricians | Mc Kinleyville · Humboldt County | — | — |
| Coonrod Construction | Garrett Leon Coonrod | — | (707) 499 8774 | GC, remodel, ADU | Bayside · Humboldt County | — | — |
| Cooper Construction | Jordan David Cooper | — | (707) 798 0400 | GC, remodel, ADU | Mc Kinleyville · Humboldt County | — | — |
| Cormier Construction | Gary John Cormier | — | (707) 445 2975 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Corn Construction | Jaycob Caleb Corn | jake@cornconstruction.com | (707) 407 6966 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Cornerstone Construction | William Thomas Lenhoff | gwebb@cornerstone-construction.com | (832) 259-2520 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Cory Sutton | Cory Sutton | — | (707) 502 6585 | GC, remodel, ADU | Ferndale · Humboldt County | — | — |
| Cosseboom Construction | Jaime William Cosseboom | — | (707) 499 4893 | GC, remodel, ADU | Eureka · Humboldt County | — | — |
| Costanzo Tile Company | Joseph Christopher Costanzo | — | (707) 496 4765 | Other | Eureka · Humboldt County | — | — |