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Find Addition to existing structure builders in Diablo

Avatar for E&J Builders Inc

E&J Builders Inc

33 Valley Dr.
5.00(
3
)
•Approved Pro

E&J Builders Inc

33 Valley Dr.
5.00(
3
)
•Approved Pro
Customers say: Quick response
Recommended by 100% of Angi customers
Recommended by 100% of HomeAdvisor customers
17 years of experience

E & J Builders was founded by husband and wife team Eric & Jane Sterken. E & J Builders is dedicated to providing quality craftsmanship, clear communication, fair prices, and a really positive attitude! We know there are many things to consider when choosing a contractor: capabilities, schedule, cost and good communication. It’s important to choose someone you feel comfortable working with and having in your home.

"We did a massive home remodel with Eric and his team at E&J, and they were phenomenal. The scope of the project was bigger than we expected, and we were in over our heads, and Eric helped at each step of the way. He worked closely with our architect and the city inspectors to finish up our beautiful home. I've recommended him to a number of friends. Their bid was well below the others we got, and they really delivered. It was to the studs/new foundation in almost half the house, the scope was across new bathrooms, kitchen, bedrooms, windows, floors, electrical plumbing, attic, roof deck and more. He managed all the complexity and subcontractors. Not only has he stood by all the work to make sure all the details were right, but he's just a genuinely nice and wonderful person who is a pleasure to work with. Highly recommend him and his team."

Ben F on April 2024

E & J Builders was founded by husband and wife team Eric & Jane Sterken. E & J Builders is dedicated to providing quality craftsmanship, clear communication, fair prices, and a really positive attitude! We know there are many things to consider when choosing a contractor: capabilities, schedule, cost and good communication. It’s important to choose someone you feel comfortable working with and having in your home.

"We did a massive home remodel with Eric and his team at E&J, and they were phenomenal. The scope of the project was bigger than we expected, and we were in over our heads, and Eric helped at each step of the way. He worked closely with our architect and the city inspectors to finish up our beautiful home. I've recommended him to a number of friends. Their bid was well below the others we got, and they really delivered. It was to the studs/new foundation in almost half the house, the scope was across new bathrooms, kitchen, bedrooms, windows, floors, electrical plumbing, attic, roof deck and more. He managed all the complexity and subcontractors. Not only has he stood by all the work to make sure all the details were right, but he's just a genuinely nice and wonderful person who is a pleasure to work with. Highly recommend him and his team."

Ben F on April 2024

North Point Construction and Restoration, Inc.

5114 Port Chicago Hwy B
New on HomeAdvisorNew on HomeAdvisor
•Approved Pro

North Point Construction and Restoration, Inc.

5114 Port Chicago Hwy B
New on HomeAdvisorNew on HomeAdvisor
•Approved Pro
8 years of experience
Free onsite estimate

At North Point Construction and Restoration, Inc., we pride our company on reliability, great communication, integrity, and quality work that customers can believe in. We are experts in our trade and will do our best to keep you as educated as we can on your particular task or project. We look forward to earning your business and working with you! 20 years of experience.

At North Point Construction and Restoration, Inc., we pride our company on reliability, great communication, integrity, and quality work that customers can believe in. We are experts in our trade and will do our best to keep you as educated as we can on your particular task or project. We look forward to earning your business and working with you! 20 years of experience.

Avatar for Fixit Construction, Inc.

Fixit Construction, Inc.

184 Bowling Green Street
3.00(
1
)
•Approved Pro

Fixit Construction, Inc.

184 Bowling Green Street
3.00(
1
)
•Approved Pro
Customers say: Terrific value
Recommended by 100% of Angi customers
Recommended by 100% of HomeAdvisor customers
11 years of experience

We pride our company on reliability, great communication, integrity, and quality work. We are experts in our trade and will do our best to keep you as educated as we can on your particular task or project. We look forward to earning your business! Book with us online or feel free to give us a call today!

"They were professional and completed the project on time."

Elizabete T on September 2016

We pride our company on reliability, great communication, integrity, and quality work. We are experts in our trade and will do our best to keep you as educated as we can on your particular task or project. We look forward to earning your business! Book with us online or feel free to give us a call today!

"They were professional and completed the project on time."

Elizabete T on September 2016

Avatar for UNITED C CONSTRUCTION, INC

UNITED C CONSTRUCTION, INC

1900 Powell Street Suite 700
5.00(
3
)
•Approved Pro

UNITED C CONSTRUCTION, INC

1900 Powell Street Suite 700
5.00(
3
)
•Approved Pro
Customers say: Quick response
1 years of experience
Free onsite estimate

We pride our company on reliability, great communication, integrity, and quality work. We are experts in our trade and will do our best to keep you as educated as we can on your particular task or project. We look forward to earning your business!

"Updating our home was a dream we have had for years. But finding a good contractor in Bay Area was so difficult, that we almost gave up. We were introduced to United C Construction by our architect(who we also love!) It was exhausting trying to find someone trustworthy and not overpriced. We had luck of working with Osmar which during the project we had clear communication, expectation of setting, professionalism and superior craftsmanship. He walked us through every step of the way, and helped problem solve tough permitting and structural issues in Berkeley!"

Shelby R on September 2024

We pride our company on reliability, great communication, integrity, and quality work. We are experts in our trade and will do our best to keep you as educated as we can on your particular task or project. We look forward to earning your business!

"Updating our home was a dream we have had for years. But finding a good contractor in Bay Area was so difficult, that we almost gave up. We were introduced to United C Construction by our architect(who we also love!) It was exhausting trying to find someone trustworthy and not overpriced. We had luck of working with Osmar which during the project we had clear communication, expectation of setting, professionalism and superior craftsmanship. He walked us through every step of the way, and helped problem solve tough permitting and structural issues in Berkeley!"

Shelby R on September 2024

Avatar for Atlantis Remodeling

Atlantis Remodeling

2010 El Camino Real
5.00(
5
)
•Approved Pro

Atlantis Remodeling

2010 El Camino Real
5.00(
5
)
•Approved Pro
Customers say: Quick response
4 years of experience
Free onsite estimate

Atlantis is a boutique business that prioritizes delivering superior customer service. We believe in going above and beyond to ensure our clients receive nothing short of exceptional treatment. Joel takes great pride in providing personalized attention to every customer. At Atlantis, we consider each client a valuable part of our exclusive clientele. Join us and experience premium service that exceeds expectations.

"We build an 400 sqft addition to our living room and made some change to the layout of our home as well , In summary, working with Joel and Avi was a great experience all around. The communication was excellent, the job was done quickly and cleanly, and the end result is absolutely fantastic. I would highly recommend them to anyone in need of home renovation and construction work."

Eric S on July 2023

Atlantis is a boutique business that prioritizes delivering superior customer service. We believe in going above and beyond to ensure our clients receive nothing short of exceptional treatment. Joel takes great pride in providing personalized attention to every customer. At Atlantis, we consider each client a valuable part of our exclusive clientele. Join us and experience premium service that exceeds expectations.

"We build an 400 sqft addition to our living room and made some change to the layout of our home as well , In summary, working with Joel and Avi was a great experience all around. The communication was excellent, the job was done quickly and cleanly, and the end result is absolutely fantastic. I would highly recommend them to anyone in need of home renovation and construction work."

Eric S on July 2023

AM GENERAL CONTRACTOR

2341 W Ave #133
5.00(
2
)
•Approved Pro

AM GENERAL CONTRACTOR

2341 W Ave #133
5.00(
2
)
•Approved Pro
Customers say: Quick response
Recommended by 100% of Angi customers
Recommended by 100% of HomeAdvisor customers
22 years of experience

We take great pride in our experience, expertise, quality and customer service that we provide to meet every consumer's needs. It is our mission to provide excellent customer service from start to completion of a project. To understand the needs and expectations of our customers, we take great care to work and communicate with every customer in a personal and professional manner. Our reputation is based on service, safety and quality, regardless of how large or small the job.

"What ever he plans for the project,He compleat that.He is honest and fair.I will refer him to my friends and family."

Mina R on November 2020

We take great pride in our experience, expertise, quality and customer service that we provide to meet every consumer's needs. It is our mission to provide excellent customer service from start to completion of a project. To understand the needs and expectations of our customers, we take great care to work and communicate with every customer in a personal and professional manner. Our reputation is based on service, safety and quality, regardless of how large or small the job.

"What ever he plans for the project,He compleat that.He is honest and fair.I will refer him to my friends and family."

Mina R on November 2020

Avatar for Hagenbach Construction

Hagenbach Construction

2668 Cinnabar Hills Ct
4.75(
16
)
•Approved Pro

Hagenbach Construction

2668 Cinnabar Hills Ct
4.75(
16
)
•Approved Pro
Customers say: Quality work
Recommended by 93% of Angi customers
Recommended by 93% of HomeAdvisor customers
15 local quotes requested

Hagenbach Construction is a locally owned and operated company with over 40 years in business with experience in new home construction, room additions, ADU units and Casitas, kitchen and bathroom remodels and all aspects of home remodeling. Let us show you our stress-free, reliable and professional touch for any of your home needs. We're committed to excellence in customer service and professional quality workmanship. Call today to see what expertise can do for the overall value of your project.

"The finished product is nothing short of stunning. They have some incredibly talented craftsmen, and everyone that's been by so far is absolutely speechless! We plan to have them back for future projects. Remodeling is stressful and John & Amy worked diligently to address all concerns in a timely manner. We are very happy with the addition to our home."

Shayna S on August 2023

Hagenbach Construction is a locally owned and operated company with over 40 years in business with experience in new home construction, room additions, ADU units and Casitas, kitchen and bathroom remodels and all aspects of home remodeling. Let us show you our stress-free, reliable and professional touch for any of your home needs. We're committed to excellence in customer service and professional quality workmanship. Call today to see what expertise can do for the overall value of your project.

"The finished product is nothing short of stunning. They have some incredibly talented craftsmen, and everyone that's been by so far is absolutely speechless! We plan to have them back for future projects. Remodeling is stressful and John & Amy worked diligently to address all concerns in a timely manner. We are very happy with the addition to our home."

Shayna S on August 2023

Avatar for Skytech Builders

Skytech Builders

1714 Seville Way
5.00(
21
)
•Approved Pro

Skytech Builders

1714 Seville Way
5.00(
21
)
•Approved Pro
Customers say: Quick response
Recommended by 100% of Angi customers
Recommended by 100% of HomeAdvisor customers
141 local quotes requested

Welcome to Sky Tech builders, a general professional construction company. Our Decades of experience in the construction and home improvement Industry will help you achieve all your dreams and have the home you always wanted. At Sky Tech we are not just general contractors, we are also homeowners. We know what it’s like to have a big home improvement project in front of you. But we also know the satisfaction of the finished job, enjoying a new, updated home that you created. That’s why we are dedicated to making it as easy as possible for you to get exactly what you are seeking. As a construction company we want to help each and any of our customers accomplish their dreams of a complete home renovation. Our mission is to give you the best quality products and customer service making you and us enjoy this mutual adventure. We guarantee your satisfaction, and we won’t leave until the job is done right. We pride ourselves on the quality work we provide, while delivering great customer service! Check out our services offered and call or click to schedule an estimate today!

"The Hall and Master Bathrooms were fully renovated with new cabinets, countertops, showers and fixtures. Leo from Skytech assisted me along the way with option choices and recommendations. The crew was exceptional in their workmanship and were very detail oriented and made sure to clean the area prior to departure each day. I have received multiple compliments on the finished bathrooms. I would highly recommend Skytech Builders to anyone considering renovations and Leo in particular."

Bob H on July 2025

Welcome to Sky Tech builders, a general professional construction company. Our Decades of experience in the construction and home improvement Industry will help you achieve all your dreams and have the home you always wanted. At Sky Tech we are not just general contractors, we are also homeowners. We know what it’s like to have a big home improvement project in front of you. But we also know the satisfaction of the finished job, enjoying a new, updated home that you created. That’s why we are dedicated to making it as easy as possible for you to get exactly what you are seeking. As a construction company we want to help each and any of our customers accomplish their dreams of a complete home renovation. Our mission is to give you the best quality products and customer service making you and us enjoy this mutual adventure. We guarantee your satisfaction, and we won’t leave until the job is done right. We pride ourselves on the quality work we provide, while delivering great customer service! Check out our services offered and call or click to schedule an estimate today!

"The Hall and Master Bathrooms were fully renovated with new cabinets, countertops, showers and fixtures. Leo from Skytech assisted me along the way with option choices and recommendations. The crew was exceptional in their workmanship and were very detail oriented and made sure to clean the area prior to departure each day. I have received multiple compliments on the finished bathrooms. I would highly recommend Skytech Builders to anyone considering renovations and Leo in particular."

Bob H on July 2025

OM & K BUILDERS COMPANY

14495 Russo Rd # 1140093
5.00(
1
)
•Approved Pro

OM & K BUILDERS COMPANY

14495 Russo Rd # 1140093
5.00(
1
)
•Approved Pro
Free onsite estimate

OM & K BUILDERS COMPANY is a locally owned and operated company that values honesty and integrity in all aspects of our business. Our dedicated team of professionals have years of hands-on experience, to provide innovative ideas and suggestions tailored to your projects. Our services are customized to your individual needs, paying close attention to the details of each project that we are involved with. Please feel free to contact us today!

"We had a great experience with OM&K. They were on time, on budget and worked day and night (and weekends) until the job was done. Great outcome and easy to work with. Definitely recommend. "

david h on September 2025

OM & K BUILDERS COMPANY is a locally owned and operated company that values honesty and integrity in all aspects of our business. Our dedicated team of professionals have years of hands-on experience, to provide innovative ideas and suggestions tailored to your projects. Our services are customized to your individual needs, paying close attention to the details of each project that we are involved with. Please feel free to contact us today!

"We had a great experience with OM&K. They were on time, on budget and worked day and night (and weekends) until the job was done. Great outcome and easy to work with. Definitely recommend. "

david h on September 2025

Avatar for 360 FULL SERVICE CONSTRUCTION

360 FULL SERVICE CONSTRUCTION

3.67(
3
)
•Approved Pro

360 FULL SERVICE CONSTRUCTION

3.67(
3
)
•Approved Pro
15 local quotes requested
29 years of experience

360 Full Service Construction delivers exceptional results for residential, commercial, and industrial construction projects. Our skilled team brings innovation, expertise, and attention to detail to every project. We strive to exceed client expectations by delivering projects on time and within budget, regardless of their size and complexity. Contact us to turn your vision into a reality.

"⭐ 1 Star – Unsafe, Unlicensed, and Untrustworthy Contractor I hired Fernando Soto / 360FSC Inc. for an ADU and home extension in Millbrae, and it has been one of the most stressful and costly experiences I’ve ever gone through. From the start, Soto relied on unlicensed workers for critical trades. Electrical work was unsafe and failed inspection — indoor panels were installed outside, wires were left unsecured, and essential safety breakers were missing. Plumbing was just as bad: instead of replacing the pipes as I requested on day one, his crew tied old cast iron, clay, and PVC together, even forcing larger pipes into smaller ones. This caused sewage leaks and backups. Independent inspections later confirmed major issues: Flooring – failed inspection and needs to be completely redone. Foundation – the new extension has already sunk by about 3.5 inches, creating serious structural risks. On top of that, the project stalled for months after May 19th, billing was vague, and Soto even threatened to rip out work I had already paid for. He hides behind a P.O. Box in Belmont instead of a real address, which says a lot about accountability. This contractor cuts corners, uses unlicensed trades, and leaves unsafe work behind. Do not make the mistake I did — avoid Fernando Soto and 360FSC Inc. One more red flag: a glowing “review” on this page was written by Rachel G — who is actually tied to his business. That tells you everything about how much weight to give positive reviews here."

Waifung S on September 2025

360 Full Service Construction delivers exceptional results for residential, commercial, and industrial construction projects. Our skilled team brings innovation, expertise, and attention to detail to every project. We strive to exceed client expectations by delivering projects on time and within budget, regardless of their size and complexity. Contact us to turn your vision into a reality.

"⭐ 1 Star – Unsafe, Unlicensed, and Untrustworthy Contractor I hired Fernando Soto / 360FSC Inc. for an ADU and home extension in Millbrae, and it has been one of the most stressful and costly experiences I’ve ever gone through. From the start, Soto relied on unlicensed workers for critical trades. Electrical work was unsafe and failed inspection — indoor panels were installed outside, wires were left unsecured, and essential safety breakers were missing. Plumbing was just as bad: instead of replacing the pipes as I requested on day one, his crew tied old cast iron, clay, and PVC together, even forcing larger pipes into smaller ones. This caused sewage leaks and backups. Independent inspections later confirmed major issues: Flooring – failed inspection and needs to be completely redone. Foundation – the new extension has already sunk by about 3.5 inches, creating serious structural risks. On top of that, the project stalled for months after May 19th, billing was vague, and Soto even threatened to rip out work I had already paid for. He hides behind a P.O. Box in Belmont instead of a real address, which says a lot about accountability. This contractor cuts corners, uses unlicensed trades, and leaves unsafe work behind. Do not make the mistake I did — avoid Fernando Soto and 360FSC Inc. One more red flag: a glowing “review” on this page was written by Rachel G — who is actually tied to his business. That tells you everything about how much weight to give positive reviews here."

Waifung S on September 2025

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FAQs for addition to existing structure building service projects in Diablo, CA

Yes, hidden rooms are legal, as long as they meet all local building regulations. If you sell your house, most states require homeowners to disclose full houseplans, which would include any hidden rooms.

If your secret room is a safe room, it should contain a means of communication aside from a cell phone, such as a shortwave radio. You should also have plenty of drinking water, a portable generator, emergency food supplies, blankets, pillows, flashlights, batteries and a first aid kit.

Any time you update your home’s square footage, you increase its value, but a secret room is a niche feature that doesn't rank high on every buyer’s list of must-haves. Investing your money in remodeling more common living areas like bedrooms, bathrooms, or kitchens will have a higher ROI than adding a secret room. Many secret rooms can act as entertainment spaces (think a game room or wine cellar) or quiet spaces (a library or study), so when building your secret room you may want to consider its versatility for when you’re ready to sell.

The Diablo, CA homeowners’ guide to addition to existing structure building services

From average costs to expert advice, get all the answers you need to get your job done.

See all articles
  • A renovated kitchen with a waterfall island

    HomeAdvisor’s DIY Kitchen Remodel Cost Guide looks at the cost of buying supplies and doing the work yourself. Find the key cost factors and how to cut expenses.

  • Secret room within bookcase

    HomeAdvisor's expert guide walks you through the cost to build a secret room, whether you're creating a safe room for security or a fun space to fulfil your childhood fantasies. Use this guide to help plan your secret room project and explore room, concea