Cornejos Builders ADU Construction & Home Building ADU projectLicense Verified

Cornejos Builders ADU Construction & Home Building

Serving Downey, Long Beach, Los Angeles County · Based in Downey, CA

Pricing on request — unlock Cornejos Builders ADU Construction & Home Building's ADU pricing for your project

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Cornejos Builders ADU Construction & Home Building ADU project 1
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Cornejos Builders ADU Construction & Home Building ADU project 3
Cornejos Builders ADU Construction & Home Building ADU project 4
Cornejos Builders ADU Construction & Home Building ADU project 5

About Cornejos Builders ADU Construction & Home Building

Cornejos Builders ADU Construction & Home Building is a CSLB-verified contractor listed in Los Angeles County with classification B.

6+ years building ADUs · CSLB 1065145 · B - General Building Contractor

Cornejos Builders ADU Construction & Home Building ADU pricing

Pricing varies by unit type, size, finishes, and site conditions. Unlock Cornejos Builders ADU Construction & Home Building's project pricing for your lot — free, no obligation.

Unit typeTypical sizePricing
Studio / JADU≤ 500 sq ftPricing locked — unlock to view
1-bedroom detached ADU600–750 sq ftPricing locked — unlock to view
2-bedroom detached ADU750–1,000 sq ftPricing locked — unlock to view
Garage conversion400–600 sq ftPricing locked — unlock to view
Attached ADU400–800 sq ftPricing locked — unlock to view

Pricing is unlocked per project

Share a few details and we'll send Cornejos Builders ADU Construction & Home Building's pricing for your build.

Services Cornejos Builders ADU Construction & Home Building offers

  • Detached ADUs
  • Attached ADUs
  • Garage Conversions
  • Junior ADUs (JADU)
  • Permitting

What Cornejos Builders ADU Construction & Home Building handles

Design & permitting

In-house design and full permit handling.

  • Architectural design & 3D renderings
  • Structural & Title 24 energy plans
  • City plan-check submittal & corrections

Construction

Turnkey ground-up and conversion builds.

  • Foundation & framing
  • Detached, attached & garage-conversion ADUs
  • Electrical, plumbing & HVAC

Financing

Guidance and lender introductions.

  • Renovation / construction-loan guidance
  • HELOC & cash-out refinance referrals
  • ADU-specific (after-build-value) lenders

Project types

ADU formats this builder takes on.

  • Detached ADU
  • Attached ADU
  • Garage / ADU conversion

Warranty & support

What's covered after move-in.

  • Workmanship warranty
  • Manufacturer materials warranties
  • Dedicated project manager

Reviews of Cornejos Builders ADU Construction & Home Building

4.636 reviews
Verified

Alex and his team were very easy to work with. They helped us build a JADU and ADU. He handled the planning and permitting of both units. As well as the inspections. He was very helpful when we had questions and made sure to maintain excellent communication with us. I would recommend Alex and his team to anyone looking for a good contractor. He’s also a pretty cool guy and will make you feel comfortable as these projects can make people uneasy.

Esther Rosas0 found this helpful
Verified

Alexsander did an amazing job for me, I hired him for my project in Downey. He was very professional, clean, responsive and got the job done in a timely manner. As problems came up during construction, he presented solutions right away. He built from the ground a two-story apartment and converted a garage into an ADU. The cost of the construction was decent and the quality in material and labor was great. I would hire him again and I have been looking for other projects to do with him already.

Chris0 found this helpful
Verified

After getting few bids from different general contractors I was referred to Cornejos Building Inc I reached out met Alex the owner of the company at one of his sites since the day I met him until the end of the project Alex was professional and courteous. Once I made up my mind to move forward with my project I made the decision to hire Cornejos Building before we started demolition Alex asked me what was important to me I stated communication and stress free process, Alex listened and delivered he communicated with me every step by step throughout the entire project he made the project a breath of fresh air. If you are looking to do any type of construction, remodel I would recommend to consider hiring Cornejos Building Alex and crew are knowledgeable, honest and extremely efficient and their work is flawless. I can’t thank enough Alex and his crew for making my project seamless and stress free. Thank you Alex can’t wait to work with you again in the future.

Sandra Silva0 found this helpful
Verified

Alex is very responsive and easy to talk with. He was highly endorsed by a satisfied coworker with whom he completed a roof project. Alex and his team Cornejos Builders Inc completed our roof project quicker than expected. He came on-site and explained thoroughly the work they have done to our roof. The workers are very professional as well, they cleaned up after the job was done, and it was not messy at all. I will be using Cornejos Builders Inc in the future

Edith Rangel0 found this helpful
Verified

After browsing some time to find a contractor that met our standards, we finally had the pleasure to work with Cornejos Builders. From the beginning of the project to the end Alex and his team committed to being consistent with communication in every aspect and was extremely informative when we had any questions regarding the project. They turned our existing garage into a comfortable and livable space which is exactly what we wanted! The garage was converted into an ADU and was completely renovated from inside and out. Not only did it add value to our home but also brought much satisfaction to our friends and families when visiting. It really helped that he was flexible with our budget and was able to compromise on a price with us. The price was very reasonable considering how efficient and outstanding everything turned out to be. We really appreciate someone that is thorough from the beginning and Alex proved himself that he is dynamic, professional and coordinates well to our needs. We are extremely content with the final product and will definitely be considering any future projects with Cornejos Builders.

alondracastillo10 found this helpful

Frequently asked questions about Cornejos Builders ADU Construction & Home Building

What does Cornejos Builders ADU Construction & Home Building offer?

Cornejos Builders ADU Construction & Home Building is a full-service ADU builder serving Downey, CA, handling design, permitting, and turnkey construction for detached ADUs, attached ADUs, garage conversions, and junior ADUs (JADUs). Cornejos Builders ADU Construction & Home Building holds a 4.6-star rating across 36 verified homeowner reviews.

Is Cornejos Builders ADU Construction & Home Building licensed and insured?

Yes. Cornejos Builders ADU Construction & Home Building holds an active CSLB license (1065145), classified B - General Building Contractor, and is bonded and insured.

How much does Cornejos Builders ADU Construction & Home Building charge to build an ADU?

Cornejos Builders ADU Construction & Home Building prices every ADU per project — your cost depends on size, finishes, and site conditions. Garage conversions are the most affordable path; detached units cost more. Pricing is unlocked per project: request a quote to get Cornejos Builders ADU Construction & Home Building's exact, no-obligation estimate for your lot.

What areas does Cornejos Builders ADU Construction & Home Building serve?

Cornejos Builders ADU Construction & Home Building builds ADUs in Downey, Long Beach, Los Angeles County.

How long does Cornejos Builders ADU Construction & Home Building take to build an ADU?

Most ADU projects run 6–12 months end to end — roughly 1–2 months for design and permitting (California caps plan check at 60 days for compliant units) and 4–8 months of construction. Cornejos Builders ADU Construction & Home Building confirms a timeline for your specific project during the feasibility consultation.

How do I get a quote from Cornejos Builders ADU Construction & Home Building?

Tap any "Get a Quote" button on this page to share a few details about your property and project. We'll confirm your service area, match you directly with Cornejos Builders ADU Construction & Home Building, and set up your free feasibility consultation — no obligation.

Where Cornejos Builders ADU Construction & Home Building works

Downey, CAService-area map
Street View
  • City Building & Safety
  • Planning Department
  • Permit Center

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