ADU Building Timeline

What are key milestones in permitting and construction for your ADU project? The Cottage team covers the key steps to your ADU construction

Updated Nov 24, 2021

With Accessory Dwelling Units exploding in interest and volume across California, more and more homeowners want to know what the construction process looks like for their own potential ADU project. In this post, Cottage team member Zachary Ackerman covers all the key milestones and details for constructing an ADU from start to finish.

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The ADU Construction Timeline & Process

Should you go with an ADU provider with industry knowledge and expertise like Cottage, your custom ADU timeline will look like the following:

ADU Design & Development: 4-6 weeks
ADU Permitting: 2-4 months
ADU Construction: 4-5 months

However, with other Design-Build and independent contractors, your timeline could easily double or triple in length. That's where Cottage brings immediate value to your project.

Let’s break down each of these three key areas for your ADU project after you’ve committed to the project.

ADU Design & Development

One of the first steps towards building your ADU from the ground up is to take a preliminary idea—be it a sketch, base floor plan, or schematic design—and have a design studio or architect develop the plans into a full architectural set and prepare the drawings for submission to the city or county that oversees your property.

Specialized ADU companies should be able to condense the feedback and development cycle to 4-6 weeks (potentially faster if you know exactly what you are looking for up front), ensuring that you don’t lose valuable time up front during the initial drafting stage. In addition, your architect or designer should coordinate with the 3rd party structural, energy, and site survey consultant(s) that will be required for your specific property or municipality.

What sets ADU providers apart during this stage is not only the speed but also the quality of design execution during this phase. Having covered the full spectrum of ADU use cases and custom design choices, the Cottage design team can help you make the best decisions for you and your property’s unique needs.

ADU Permitting

Now that you’ve designed your dream ADU, the next step is to get the city or county’s permission to build it.

Every municipality is different—with different regulations, processes, forms, and employees—which can make permitting difficult to navigate. If you or your designer get part(s) of the permit application wrong, it can cost you weeks, or even months, as you wait for the city’s reviewers to send you multiple rounds of corrections for seemingly the tiniest of nitpicky details.

Because planning and building departments are consistently swamped with permit applications, each revision of your application can take 3-6 weeks to review. ADU-specializing companies like Cottage know what the city’s planning and building officials are looking for. From uploading the right forms to the right online portal to what small details are needed on your ADU’s site plan, this expertise ensures you minimize the number of revisions needed to earn approval.

The Cottage Operations team has processed the full spectrum of ADU permit applications. With knowledge of local processes and key contacts, they can streamline your permitting timeline by ensuring a high-quality application and consistent follow up with the right people.

ADU Construction

After your ADU is permitted and the plans sets are stamped to be used for construction, that’s when the rubber hits the road. Once you have confirmed your ADU builder, your project will go through some key milestone steps:

Site Preparation and Foundation Pour: Your builder will need to get the site ready for construction. This might include demolition of a shed or garage, grading your yard to provide a flat surface, or removing brush and small trees. Then your builder will need to pour a high-quality foundation that will keep the ADU safe and pass a special grading inspection with the city or county.
Framing, Drywall, and Roofing: Your builder will need to translate your permitted plans and structural drawings into a real-life physical building. The right builder will have planned this process meticulously to ensure that everything comes together in a streamlined manner.
Plumbing and Electrical: A good general contractor will hire the right subcontractors who show-up on time, every time. These licensed plumbers and electricians need to design and install systems that deliver water and electricity to and remove waste from your ADU safely and efficiently.
Utility Work: Every municipality regulates its water and sewer utilities differently. For example, some cities allow an ADU to tap right into the main home’s sewer system while others expect you to trench all the way to the sewer main on the street. An expert builder knows what the city needs and how to deliver it.
Doors and Windows: Doors and windows may seem simple, but they require a long lead time to procure at a reasonable cost. Trusted general contractors have the right relationships to acquire your perfect windows and doors at a great price and without delay, and pass on those cost savings to you.
Fixtures and Finishes: These small details—like doorknobs, light fixtures, tile, and flooring—bring the ADU together. In traditional construction, it’s common for these items to be overlooked or ignored bids and planning. However, a builder focused on ADUs knows exactly what is needed to ensure you get an accurate cost estimate for the entire cost of your ADU project.
Inspections: Throughout construction, the city will send inspectors to verify your ADU is being built properly. A failed inspection can cause serious delays and rework, blowing up your timeline and budget. Cottage’s vetted network of licensed general contractors have decades of experience preparing for and passing inspections. They know the officials and build code better than anyone.

Overall, this detailed process typically takes 4-6 months to complete. However, if your builder runs into issues with sequencing the different steps, dropping the ball when lining up subcontractors and ordering materials, or there are steps that need to be re-done, this timeline can quickly extend beyond the initial estimate—even double or triple the time!

However, with experience permitting and building ADUs across hundreds of projects, the Cottage team ensures that your project is completed on time and up to code every time.

Your ADU Building Timeline

Just as no property is exactly the same, no single custom ADU construction process is exactly the same. In order to reach and even surpass the timelines laid out for your ADU project in this article, you need a team of ADU experts that have designed, permitted, and built a full range of ADUs.