Keith Stone

Founder and President

Keith Stone - Diamond ConstructionKeith Stone, founder and owner of Diamond Construction, has worked in the construction industry for over 38 years. Keith began his construction career in 1975 with Steen Construction, who ultimately became Heritage Auxiliary Builders. While working with Heritage, Keith successfully completed the Apprenticeship, Journeymanship and Foremanship before becoming a superintendent. After 10 years, Keith branched out to start the Diamond Construction Company where he remains today serving as the President and Founder. His integrity, combined with his passion for the construction industry, has made Diamond Construction successful for over 25 years.

Keith’s expertise is widely acknowledged in the Bay Area by attorneys who seek his services as an expert witness. He has successfully worked for over 30 attorneys and acted as a construction expert in more than 100 construction defect cases.

Keith has two sons and a daughter and enjoys snow skiing, water skiing, scuba diving, cycling and traveling.

Jeff Stone J.D., Broker

Asset and Project Manager

Jeff Stone - Diamond ConstructionJeff Stone, Keith’s youngest son, has worked for Diamond Construction since he was 15 years old. Jeff began working for Diamond Construction as a laborer and today wears two hats as the Asset & Project Manager and go-to Real Estate Broker.

After graduating from Acalanes High School, Jeff attended the University of California, Los Angeles where he earned a B.A in Communications and a B.A in Political Science. Thereafter, he attended law school at the University of California at Davis.

While in Law School, Jeff lived in Beijing, China where he worked for the US China Green Energy Council as the Deputy Director of China Business Development.  Jeff earned his Juris Doctorate in July 2010 and became a member of the California State Bar in November 2010. During his brief career stint in Law, Jeff worked in construction defect litigation and real estate litigation for Eugene Haydu Esq. located in Sacramento, California.

Jeff’s experience in construction defect litigation helps him anticipate problems before they occur. At Diamond Construction, Jeff is working to become more fully integrated in sustainable building and the use of green technologies. As one of Diamond’s internal real estate brokers, Jeff understands the complexities of transactional business and has the ability to assist clients in asset acquisition.

Jeff is an avid skydiver, enjoys snowboarding, wakeboarding, motorcycles and golf. Jeff became a licensed Real Estate Broker in March 2011.

Toni Cowen

Office Manager

Toni Cowen - Diamond ConstructionToni Cowen has been the Office Manager for Diamond Construction since 1999. Before coming to Diamond Construction, she worked as a meeting planner for the Council on Education in Management.

Toni grew up in El Sobrante, California and has been a native of Northern California her entire life. After graduating from high school, Toni attended Foothill College where she studied Animal Health Technology. She then worked as a Registered Animal Health Technician for the Albany Veterinary Clinic and thereafter, worked in Human Resources for both Accutax systems and Travelers Insurance.

Toni’s exceptional ability to organize and manage construction projects is an incredible asset to every team member involved in a project.  Her managing skills assist sub-contractors while also holding them accountable for their duties. Toni is a highly organized leader ensuring each projects clear and timely path.

Toni has two children whom both attend the University of California, Davis. Her interests include waterskiing, snow skiing, gardening horseback riding and cheering on the San Francisco 49ers.

Jim Peirce


Jim Peirce - Diamond ConstructionFor over 27 years, Jim has served as the Superintendent at Diamond Construction overseeing and managing residential and commercial construction projects. His unique ability to understand and complete difficult building tasks sets Jim at the top of his profession.

Jim was born and raised in Alameda, California. After graduating from high school, Jim attended Brigham Young University, where he studied graphic design. He later transferred and graduated from California State University, Hayward with a Bachelors of Arts in Accounting.  While working on his B.A, Jim worked full time for Heritage Auxiliary Builders as a project manager.

Jim has five children and he is an avid cyclist. He also enjoys mountain climbing, exercising, rappelling and the outdoors. Jim has been a dedicated volunteer for the Boy Scouts for America for over 15 years.

Oscar Hernandez


Oscar Hernandez - Diamond ConstructionSince 1989, Oscar has been proven to be an invaluable team member at Diamond Construction. Initially starting as a full-time carpenter, Oscar was promoted to full time Superintendent in 1999 at Diamond Construction. Oscar is known for his realistic and calculated approach to building and ability to manage residential and commercial projects.

Born in Puebla, Mexico, Oscar migrated to the United States in 1985 after completing high school.  Oscar immediately began working in the construction industry and has over 25 years of hands on experience building everything from commercial tenant improvements to high-end custom homes.

Oscar is a father of three sons ranging in age from 18 to 2 years old. He enjoys watching soccer, the San Francisco Giants and the Golden State Warriors.


Office Dog

Buddy the Office Dog - Diamond ConstructionBuddy is an 8 year old yellow Labrador who enjoys the lounging around side of construction. He prefers not working at all, but if he must, milk bones and peanut butter are good motivating factors. He oversees the human resources department by monitoring office happiness. Buddy is always available to play ball and loves to swim.