How Long Does it Take to Build an ADU (Accessory Dwelling Unit)?

Life is full of big decisions. Some revolve around career paths, love lives, or whether you should get that extra slice of pizza (the answer is always yes!). But have you ever thought about the time it would take to build an accessory dwelling unit (ADU)? 

Whether it’s an attached ADU, a detached additional dwelling unit, or a junior accessory dwelling unit, the question remains the same: “how long does it take to build an ADU?”

Why Build an ADU

ADUs, also known as accessory dwelling units, have risen in popularity for many reasons. Perhaps it’s the allure of having extra living space, the potential for passive income from renting it out, or the opportunity to increase property value. Sometimes property owners start ADU construction pursuing not material, but spiritual values, for example, try to realize the goal of creating a dream house. Whatever your reason, let’s face it, building an ADU is a significant endeavor that comes with its own set of challenges and timelines.

Before we delve into the exact time estimates, it’s essential to acknowledge that building an ADU isn’t just about the construction. The entire process includes design, permitting, and finally, the build itself. Now, let’s unravel this ADU-building enigma, shall we?

How to Manage Your Accessory Dwelling Unit

If you were engaged in the construction of your main residence, you know that this is a very complex process that is not limited to the creation of a realistic budget and the formation of construction guesswork about additional costs. 

If not, now we will tell you about all the steps in detail, but for now, the first tip is that you and your contractor should give an accurate estimate to each stage of new construction, so no matter what project you are planning to implement, whether it is detached ADU, which is located separately from primary home or prefab ADU, revolving crews are not suitable for this purpose, because the key to success lies in regular and close cooperation.

  • Schematic Design Meeting

Every great ADU project starts with a schematic design meeting. Think of this as a brainstorming session where you share your ADU’s floor plan ideas, layout customizations, and overall vision with the design partners or the ADU builder – read more about here – There are a huge number of ADU designs, because it is a completely customized type of building, so most designers advise taking into account the purpose of ADU using, because this factor can influence the final draft of ADU design. This phase usually lasts about 2 to 3 weeks.

  • Design Development Meeting

This phase involves refining the design, taking into account practical concerns like local and state agencies regulations, unit size, and structural changes. Here, you’ll finalize the ADU plans and move towards acquiring the necessary building permits, which might take 2-4 weeks.

  • Permit Research

Permit research is where you roll up your sleeves and tackle the nitty-gritty details. You’ll need to ensure that you have all the correct building permit forms, understand what’s required by local and state agencies, and have plans in place for sewer lines and utility hookups. 

At this stage, the building process you need to study everything like under a microscope, because, for example, not many people know that when implementing basement conversions, it is required to set a ceiling height different from primary residence, and if we are talking about attic conversions, then special fire safety measures are prescribed for such ADU projects, the availability of which you should provide to city planners. Remember, ignorance is not bliss when dealing with construction permits. 

This phase can take around 6–12 weeks, so patience is key.

  • Construction Drawings

In this phase, construction drawings are developed based on the final plans. They include specific technical details and specifications that a general contractor will follow during the ADU construction. This process can take anywhere between 3 and 5 weeks.

  • Building Permit

Once your construction drawings are complete, you can apply for a building permit. The timeline for permit approval varies significantly based on the local agency’s workload, the ADU type, and the completeness of your application. In order not to delay the process with ADU permit, make an appointment with the local authorities in advance. Typically, this process can range from 8 weeks to six months.

  • Site Prep

After obtaining the necessary permits, you can move to the next step of ADU build process, namely, the site preparation. This involves clearing dirt, ensuring proper drainage, and making the site safe for workers. After the site measure, don’t forget to request a soils engineering report to avoid additional expenses in the future. Depending on the project’s scale, this could take around 1–2 weeks.

  • Construction Phase

Finally, we come to the construction phase. This is where the magic happens, and your ADU starts to come alive! The duration depends on many factors, including the size of the unit, the complexity of the design, availability of sustainable materials, and potential delays due to bad weather or unforeseen site conditions. On average, construction of an ADU takes between 4 and 6 months.

  • Final Inspection

Once the construction is complete, the final inspection takes place to ensure the ADU is built according to the approved plans and local building codes. The inspector will check the ADU thoroughly before giving their approval. This process typically takes a week.

ADU Construction Timeline: Final Thoughts

In conclusion, most homeowners should expect the process of building an ADU to take anywhere from 9 months to over a year from the initial design phase to the final project completion. 

However, remember, building an ADU is not just about adding another structure on your property; it’s about creating an independent housing unit that provides additional living space or income.

Frequently Asked Questions — FAQ

How long does it take to build an ADU? 

On average, the entire process from design to completion takes anywhere from 9 months to over a year.

How long is the construction phase for an ADU? 

The construction phase for an ADU generally takes between 4 and 6 months, depending on the size and complexity of the design, for example, the construction of a standard ADU will end faster than a fully customized single family home.

Why do I need a permit to build an ADU? 

Permits ensure that the construction adheres to local and state building codes and safety standards. It also ensures your ADU is legally recognized by local and state agencies. In order not to miss a single legal detail in creating a brand-new ADU, we recommend signing up for at least a free consultation with a specialist.

How long does the design phase of an ADU take? 

The design phase, including schematic design meeting and design development meeting, can take about 4 to 7 weeks, however, if plans, requests, and ideas regarding the design of the new ADU change, then a follow-up meeting may be required.

How long does it take to get a building permit for an ADU? 

The timeline for getting a building permit can vary greatly, ranging from 8 weeks to six months, depending on various factors, the most important of which is the scale of the project, e.g., the construction process of a detached single family dwelling unit will take longer than an attached JADU.

Can I build an ADU in my existing garage? 

Yes, you can convert your existing garage into an ADU, provided you obtain the necessary permits and the garage meets specific requirements set by local and state agencies.

Can I build an ADU myself? 

While it’s possible, it’s advised to hire professionals to ensure the construction meets the building codes and safety standards. Remember, patience is key. Building an ADU is a significant investment in time and resources. But, at the end of the day, the comfort and convenience it offers are well worth the wait. Happy building!