ADU Design & Construction
Whether you’re looking to create extra living space for family members, generate rental income, or simply add more functionality to your property, our team is here to make the process smooth and enjoyable.
Build Your Custom Home With Nejasmich Developments.
At Nejasmich Developments, we bring the same level of personalization and craftsmanship to Accessory Dwelling Units (ADUs) as we do with our custom homes.
What Is an ADU?
An Accessory Dwelling Unit, or ADU, is a secondary housing unit located on the same lot as your primary residence. ADUs can take many forms—a separate backyard cottage, a converted garage, or an attached apartment. They offer a flexible way to expand your living space without the need for a full-scale home renovation.
Tailored to Your Vision
At Nejasmich Developments, we understand that every ADU should be as unique as your home. That’s why we take a personalized approach to every project, working closely with you from the very beginning to ensure your ADU perfectly complements your property and lifestyle. Whether you already have specific ideas in mind or need a little guidance, we’ll collaborate with you to create a space that meets your needs, all while adding value to your property.
Designed for Your Needs
ADUs are a great way to maximize your property’s potential, and we design each one to fit seamlessly with your existing home. From guest suites to home offices or independent living spaces for relatives, we’ll help you choose the right layout and finishes to ensure your ADU blends practicality, comfort, and elegance. Every aspect of the design is fully customizable, so you can feel confident that your ADU will serve your specific goals, whether it’s providing a flexible living arrangement or creating a stylish rental unit.
A Seamless Process
Our team is here to make the ADU building process as straightforward and stress-free as possible. From securing permits to managing the construction timeline, we handle all the details. We use a project management software to keep you informed and engaged throughout every phase of the build. With our transparent communication and focus on quality, you’ll always know where your project stands, and you can trust that every element of your ADU will meet the highest standards.
Quality You Can Trust
At Nejasmich Developments, we pride ourselves on delivering craftsmanship that lasts. Your ADU will be built with the same attention to detail and quality materials as our custom homes, ensuring it’s not only a functional space but also an investment that will stand the test of time.
KIND WORDS FROM OUR CLIENTS
“We had the best experience working with Matt and Dan Nejasmich on our Hillsborough home. They have a great team and went above and beyond to make sure our project was done right. They are organized and detail oriented- they were extremely thoughtful about the whole process and did not just blindly follow plans. They made suggestions, improvements, and were partners with us all along the way. They were open and honest with all of our communication. I always trusted them knowing they were building our house as if it were their own. We have worked with other contractors before and the difference working with Matt and Dan was night and day. I cannot recommend them highly enough! Would definitely use them again in the future!!!”
-Tina Tan
“I can’t say enough good things about Nejasmich Developments. Matt and Dan built our house in 2018/2019. Their attention to detail, the quality of their construction and materials, and their ongoing level of proactive maintenance for us has been top notch. They are local guys (grew up in Bay Area), take a great deal of pride in what they do, and it shows. Anytime we have had questions with the house or needed something addressed, they have come by promptly and really possess an ownership mentality (and this is several years after we moved in). We feel incredibly lucky to have found them. I can confidentially vouch for them as people and developers.”
-Nikhil Trikha
Beneifts Of Owning An ADU
Additional Rental Income
Flexible Living Options
Increased Property Value
Adding an ADU generally increases the overall value of your property. Many buyers see ADUs as a bonus, making your property more attractive and potentially more profitable if you ever decide to sell.
Maximized Use of Space
Affordable Housing Solution
Aging-in-Place Option
Environmentally Friendly
Home Office or Studio
Some Examples Of Our Work
Why Choose Nejasmich?
We believe that building an ADU is about more than just adding square footage to your property—it’s about enhancing your lifestyle. Whether you’re looking for extra space, greater flexibility, or a new income stream, our team is here to make your vision a reality with a tailored, hands-on approach from start to finish.
Let’s work together to create an ADU that fits your needs and adds value to your home. Reach out to us today, and let’s start bringing your vision to life.
Expertise You Can Trust
With years of hands-on experience, our team excels in designing and building ADUs that fit any budget, from cozy, functional spaces to luxurious, high-end guest houses.
We believe that “custom” should be accessible, and we’re here to guide you every step of the way.
Serving the Greater San Mateo Area
Conveniently located in San Mateo, CA, we’re proud to serve our community and the entire San Francisco Peninsula.
No matter where you are in the area, we’re ready to bring our exceptional service and craftsmanship to your doorstep.
Personalized Design Consultations
We offer design consultations that cater to your vision, whether we start with one of our customizable plans, your plans, or create something entirely from scratch.
Share your ideas with us, and we’ll transform them into a home that’s distinctly yours.
Client-Focused Approach
At Nejasmich Developments, you’re more than just a project—you’re a partner.
From the first consultation to handing over the keys, we’re dedicated to ensuring an enjoyable and smooth home-building journey.
Frequently Asked Questions
What Is an ADU?
An Accessory Dwelling Unit (ADU) is a secondary housing unit built on the same property as a primary residence. ADUs can be attached to the main home, converted from an existing space (like a garage), or built as a standalone structure in the backyard. They are often used for rental income, guest accommodations, or housing for family members.
What Are the Benefits of Building an ADU?
ADUs offer a range of benefits, including generating rental income, providing housing for family members or guests, increasing the value of your property, and maximizing your lot’s potential. They also offer flexibility for multigenerational living or creating a home office or studio space.
How Much Does It Cost to Build an ADU?
The cost of building an ADU can vary significantly depending on factors like size, design complexity, materials, and location. On average, ADUs can range from $100,000 to $300,000, but costs can be higher or lower based on your specific project. An experienced builder can provide a detailed estimate based on your vision and budget.
How Long Does It Take to Build an ADU?
The timeline for building an ADU depends on factors like the complexity of the design, permitting process, and construction logistics. On average, the process can take anywhere from 6 to 12 months, from initial design to completion. Working with an experienced builder like Nejasmich Developments can help streamline the process and avoid delays.
Can I Rent Out My ADU?
Yes, in many areas, homeowners can rent out their ADUs for long-term tenants or even as short-term vacation rentals (depending on local regulations). Renting out your ADU can provide a significant source of additional income.
Do I Need a Permit to Build an ADU?
Yes, building an ADU typically requires permits from your local city or county. The permitting process will ensure that the ADU complies with zoning laws, building codes, and other regulations. Our team can help navigate this process to ensure all necessary permits are secured.
What Size Can My ADU Be?
The size of an ADU is typically limited by local regulations. In many areas, ADUs can range from 400 to 1,200 square feet, depending on the size of your lot and local building codes. Some areas may have specific square footage restrictions, so it’s essential to check with your city or county planning department.
Will an ADU Increase My Property Taxes?
Building an ADU can increase your property’s assessed value, which may lead to higher property taxes. However, the amount depends on the value of the addition and your local tax regulations. It’s a good idea to consult with your local tax assessor to understand the potential impact.
Do ADUs Have Separate Utility Connections?
ADUs can either share utilities with the main house or have separate connections for water, electricity, and gas. The choice depends on local building codes and your preferences. Separate utility connections can make it easier to rent out the ADU, but they may add to the cost of construction.
How Do I Finance an ADU?
There are several options for financing an ADU, including home equity loans, construction loans, and cash-out refinancing. Some areas also offer ADU-specific loan programs or incentives. It’s worth exploring financing options with your lender to find a solution that fits your financial situation.

