How To Build an ADU

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19 min read

Knowing the steps to build an ADU helps you make smart choices and get your project done the way you want, fitting both your budget and how you live.


Creating an Accessory Dwelling Unit (ADU) can really boost your home’s value and help with housing costs. Starting the journey to build an ADU takes some planning. Knowing the steps helps you make smart choices and get your project done the way you want, fitting both your budget and how you live.

ADU Development Timeline

Before diving into the detailed phases of building an ADU, it’s essential to understand the overall timeline.

Here’s a quick look at how long it takes to build an ADU

  • Design Phase

This first part, lasting 1-2 months, is when you plan out what your ADU will look like.

  • Permitting Phase

Next, for about 3-4 months, you need to get the right permits, which means following local rules.

  • Construction Phase

The building part can take 4-6 months, depending on the type of ADU and your yard.

Usually, the whole process takes about 8 to 12 months.

Phase 1: Research

Starting your ADU project begins with doing your homework. This step is key to know what you can do, what you want, and how it fits your budget.

  • Budgeting

Figure out how much you can spend, including extra costs.

  • Property Check

Look at your property’s size and shape to pick the best ADU type.

  • Local Rules

Learn about your area’s rules that will guide your ADU project.

Phase 2: Feasibility Study

The feasibility study represents a pivotal moment in the ADU development process. This important step checks if your property can handle an ADU. It looks at many things like laws, the land itself, and money stuff.

  • Look at zoning rules

Find out what you’re allowed to build.

  • Check utilities

See where things like water and electricity are to avoid extra costs.

  • Survey your property

Get a detailed look at your land to help with planning.

  • Make sure you’re following the codes

Check that your ADU plan meets all safety and building standards.

  • Talk to local planners

This helps spot any issues early on.

  • Plan your site

Make a basic plan that fits your property and follows the rules.

Phase 3: Design and Planning

Now, you start to bring your ADU to life. You’ll decide on how it looks, its layout, and what materials to use. It’s a team effort to make sure it’s just right and fits your needs. The choice of ADU design is influenced by several factors, including your property’s characteristics, budget, and specific needs.

  • Detached ADU

Stands alone, offering privacy. Costs more but gives more design freedom.

  • Garage Conversion ADU

Changes your garage into living space. Saves money but has some limits.

Adds on to your home. Less disruptive and cost-effective.

  • JADU

Small space inside your home. Good for small spots.

When planning your design, keep these in mind

  • Matching your house

Does the ADU look like your main house or different?

  • Being green

Use materials that are good for the planet and your wallet.

  • Choosing strong materials

Pick things that last long and are easy to look after.

Understanding the Impact of Your Choices

The design and planning phase also entails a clear understanding of how different design options impact costs, regulatory compliance, and the project timeline.

Design OptionEstimated Cost RangeTimeline ImplicationsRegulatory ConsiderationsMaintenance and UpkeepAccessibility and Flexibility
Detached ADU$$$LongerHigh compliance needsModerate to HighHigh flexibility
Attached ADU$$$Moderate to LongHigh compliance needs due to integration with the primary residenceModerate to HighModerate flexibility due to shared infrastructure with the primary home
Room Addition$$ModerateVaries by projectModerateModerate flexibility
Garage Conversion$ShortestLower compliance needsLowLimited space
JADU$ShorterModerate compliance needsLow to ModerateLimited by the existing structure

Phase 4: Permitting

Getting permits is a big deal in the ADU construction process. You need to make sure everything is legal and safe. This step can be tricky and take time, but it’s very important to do it right.

  • Learn the rules

Know what your local area requires for an ADU.

  • Get your papers ready

Have all your plans and documents prepared.

  • Apply for permits

Hand in your application to the local office.

  • Adjust if needed

You might need to change your plans based on feedback.

  • Get your permit

Once everything’s approved, you can start building.

Want to make the permit process easier? Follow these steps

  • Talk Early

Chat with local officials soon to know what you need to do and fix any problems before they get big.

  • Use Experts

Get help from architects or planners who know the rules well. They can make getting permits quicker and easier.

  • Be Flexible

Sometimes, you might need to change your plans a little based on advice from officials. This can help you get approved faster.

  • One-Stop Solution

Consider a one-stop shop, ensuring the entire permitting process is effortlessly managed on your behalf.

Phase 5: Building It

The ADU building phase is when your ADU plan becomes a real building. This step has many parts, all important for making sure your ADU is strong and works well. Knowing what each part involves helps keep things moving smoothly.

Here are the key steps to build your ADU

  • Get the Land Ready

Clear the land, level it, and maybe take down old buildings to prepare for your ADU.

  • Lay the Foundation

Build a strong base for your ADU, whether right on the ground, on a raised platform, or over a basement.

  • Build the Frame

Build the structure of your ADU, including the walls, floors, and roof.

  • Add the Roof and Outside Walls

Put on the roof and outer walls to keep water out and make it look good.

  • Set Up Water, Power, and Air

Install the plumbing, wiring, and heating or cooling. These need to be safe and up to code.

  • Insulate and Drywall

Insulate for warmth and cover walls inside with drywall.

  • Finish the Inside

Put in floors, paint, cabinets, and fixtures to make it a nice place to live.

  • Check Everything

Have inspectors check to make sure everything is safe and follows the rules. Then, you’re ready to go!


Embarking on the journey to build an ADU represents a meaningful investment in your home and future. With the potential to enhance your property’s value, provide additional living space, or generate rental income, informed decision-making and meticulous planning cannot be overstated. Leveraging this guide’s insights and comparative analyses equips you to navigate the ADU construction process effectively, ensuring the realization of your project’s full potential.

If you’re looking to build an ADU in San Diego, Better Place Remodeling is your premier choice. Our one-stop-shop approach simplifies the ADU design build process, providing everything you need under one roof to construct your ADU seamlessly and affordably. From initial concept to move-in, our expert team is committed to making your ADU vision a reality. Contact us today to discover how we can transform your property with a custom ADU solution.


Begin by understanding local zoning and building regulations, deciding on the type of ADU you want (detached, attached, or garage conversion), and setting a realistic budget for the entire project.

The timeline can vary, but typically it ranges from 12 to 18 months from the initial planning phase to the final construction and inspection stages.

The process generally includes submitting detailed construction plans, undergoing several rounds of review by local planning departments, and addressing any required revisions to secure the necessary building permits.

Key costly components often include site preparation and foundation work, high-quality building materials, major utility upgrades, and professional fees for architects and contractors.

Hire experienced professionals such as architects and contractors who specialize in ADUs and are familiar with local regulations. Carefully plan and review all designs and constructions to adhere to all applicable standards.

Focus on efficient layouts with open floor plans, built-in storage solutions, and multi-functional spaces that cater to both aesthetics and functionality.

Explore options such as home equity loans, personal loans, or local government grants and incentives designed to encourage ADU development.

Look for contractors with ADU experience, a good track record, valid licensing, and positive reviews. Ensure they communicate well and offer transparent pricing.

Address any feedback from the building department, make necessary revisions to the plans, and resubmit. It’s common to go through multiple revisions before gaining approval.

After completing construction, schedule a final inspection with your local building department to ensure compliance with all regulations. Once approved, the department will issue a Certificate of Occupancy, confirming the ADU is safe and ready for habitation.


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