| Kiper Development INC | Rick Philip Kiper | — | (925) 648 8888 | GC, remodel, ADU | Alamo · Contra Costa County | — | — |
| Kirby Electric INC | Adam Carl Kirby | contact@sansoxygen.com | (925) 812 1708 | Electricians | Concord · Contra Costa County | — | — |
| Kirby Floor Works | Kirby Floor Works | — | (925) 595 0786 | Other | Pacheco · Contra Costa County | — | — |
| Kirk Beck | Kirk Beck | — | (925) 451 5554 | GC, remodel, ADU | Lafayette · Contra Costa County | — | — |
| Kirk T Allen DBA Lamorinda Electric | Kirk Trevitt Allen | — | (925) 212 8157 | Electricians | Lafayette · Contra Costa County | — | — |
| Kirk Wall Construction | Kirk Shelbron Wall | — | (925) 250 5475 | GC, remodel, ADU | Orinda · Contra Costa County | — | — |
| Kissane Company | Sean Michael Joy | — | (650) 269 0102 | GC, remodel, ADU | Orinda · Contra Costa County | — | — |
| Kitchen And Bath Xpressway | David Yusuf Sherdil | — | (925) 687 7800 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Kitchen Solutions INC | Isaias Aguilarsoto | — | (925) 305 0080 | GC, remodel, ADU | Bay Point · Contra Costa County | — | — |
| Kiwi Pavers INC | Regan David Mclean | — | (925) 876 0177 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Kj Demolition INC | Joao Raimundo Nicolau | contact@kjdemolition.com | (510) 275 9994 | Other | Pinole · Contra Costa County | — | — |
| Kl Builders & Developers INC | Kit Long Lau | — | (510) 913 1316 | GC, remodel, ADU | San Ramon · Contra Costa County | — | — |
| Klaus Kubler Construction | Klaus Bernhard Kubler | — | (925) 586 0076 | Electricians | Pleasant Hill · Contra Costa County | — | — |
| Klaus Stoermer Construction | Klaus Edmund Stoermer | — | (415) 246 0094 | GC, remodel, ADU | Pinole · Contra Costa County | — | — |
| Klc Builders INC | Ronald Bongar Campos | karlconway405@msn.com | (510) 232 0300 | GC, remodel, ADU | El Cerrito · Contra Costa County | — | — |
| Kleoni Construction | Costandinos Andreas Kleoni | — | (925) 270 6323 | GC, remodel, ADU | Oakley · Contra Costa County | — | — |
| Kmn Construction | Kyle Marcelo Navarro | — | (510) 338 2749 | GC, remodel, ADU | El Sobrante · Contra Costa County | — | — |
| Knight Construction Ba INC | Adam David Knight | — | (925) 584 4855 | GC, remodel, ADU | Pleasant Hill · Contra Costa County | — | — |
| Kodiak Construction | David Gurdado Figueroa | — | (925) 685 1244 | GC, remodel, ADU | Martinez · Contra Costa County | — | — |
| Kodiak Design Build INC | Colin Mark Zak | — | (510) 482 5261 | GC, remodel, ADU | Orinda · Contra Costa County | — | — |
| Kodiak Heating & Cooling | Jose Mauricio Villanueva | info@kodiakheatingcooling.com | (925) 303 2850 | HVAC | Brentwood · Contra Costa County | — | — |
| Koester Construction | John David Koester | — | (925) 228 3444 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Komac Electric INC | John James Macdonald | admin@komacelectric.com | (925) 951 3600 | Electricians | Martinez · Contra Costa County | — | — |
| Konstructo INC | Sawhney Priyam | — | (925) 639 3674 | GC, remodel, ADU | Walnut Creek · Contra Costa County | — | — |
| Kool Concrete | Kool Concrete | — | (925) 727 7293 | Other | Pittsburg · Contra Costa County | — | — |
| Kostadin Guerguinov | Kostadin Guerguinov | — | (925) 360 7305 | GC, remodel, ADU | Concord · Contra Costa County | — | — |
| Kp Bay Area Construction INC | Kevin Ronaldinho Perez | — | (925) 303 9286 | GC, remodel, ADU | Brentwood · Contra Costa County | — | — |
| Kp Carpentry Bay Area INC | Kyle Raymond Perry | — | (510) 290 4163 | GC, remodel, ADU | San Pablo · Contra Costa County | — | — |
| Kpjm General & Electrical Contractors INC | Derek Michael Mello | — | (510) 502 4205 | Electricians | San Ramon · Contra Costa County | — | — |
| Kray Cabling INC | Heather Colleen Buckley | — | (510) 236 5500 | Electricians | Richmond · Contra Costa County | — | — |
| Krishnan | Kalliana Rughmaniamm Krishnan | — | (562) 418 9065 | Other | Brentwood · Contra Costa County | — | — |
| Kt Builders | Kurt Richard Nunnenkamp | — | (925) 382 1219 | GC, remodel, ADU | Diablo · Contra Costa County | — | — |
| Kt Home Development | Kurt Richard Nunnenkamp | — | (925) 382 2048 | GC, remodel, ADU | Diablo · Contra Costa County | — | — |
| Ktf Construction Services LLC | Kristina Paula Frasier | — | (925) 788 0208 | GC, remodel, ADU | Discovery Bay · Contra Costa County | — | — |
| Kuhlmann And Cheyne Builders INC | Kuhlmann Keith | — | (510) 715 7403 | GC, remodel, ADU | Pinole · Contra Costa County | — | — |
| Kuhltech | Brian Wayne Jr Kuhl | — | (925) 595 9292 | Other | Oakley · Contra Costa County | — | — |
| Kumnick Electric | Kohlton Shawn Kumnick | — | (925) 588 5913 | Electricians | Martinez · Contra Costa County | — | — |
| Kunga Electric | Nyima Kunga | — | (341) 247 3345 | Electricians | El Cerrito · Contra Costa County | — | — |
| Kurt Alan Rieboldt DBA Northwest Concrete | Northwest Concrete | — | (925) 570 6650 | Other | San Ramon · Contra Costa County | — | — |
| Kurt's Plumbing & Heating | Kurt's Plumbing & Heating | — | (510) 236 7100 | HVAC | Brentwood · Contra Costa County | — | — |