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

Welcome to the comprehensive guide on the journey of constructing an Accessory Dwelling Unit (ADU) – a unique and increasingly popular solution for expanding living space in urban settings.

Today we answer the frequently asked question: How long does it take to build an adu?

The most obvious answer is “it depends”. I know, no one wants to hear that but it’s true. Before we can even find out how long it takes to build an ADU, we need to answer a completely different set of questions!

1. Do you want one or two stories? 
2. How many bathrooms do you want? 
3. How many bedrooms? 
4. Do you want a driveway or immediate door access?
5. How many sqft do you have to work with? 
6. etc…

ADUs serve a bunch of purposes, there’s no doubt about it. From housing extended families to providing a rental income source, and are becoming a key part of urban development strategies, particularly in densely populated areas.

In Los Angeles, California, the rise of ADUs has been remarkable.

A recent statistic highlights this rise: In 2019 alone, the city issued permits for over 5,000 ADUs – a substantial increase from just a few hundred in previous years.

This surge reflects the growing interest and demand for ADUs in LA, driven by the city’s progressive zoning laws and the need for more affordable housing options.

As we delve into the ADU building process, we’ll explore various phases: from the initial planning and permitting stages to the nuts and bolts of construction, and finally, the post-construction formalities that make an ADU ready for occupancy.

Each stage comes with its own set of challenges and requirements, often influenced by local regulations, zoning laws, and the specific needs of a project.

Navigating through these stages requires a good grasp of industry lingo – terms like ‘setback requirements’, ‘easements’, and ‘floor area ratio (FAR)’ are essential in understanding the regulatory landscape.

Moreover, engaging with experienced architects, contractors, and local authorities is crucial in aligning your ADU project with the existing building codes and community standards.

As we break down the timeline and intricacies of building an ADU, keep in mind that factors such as the complexity of the design, availability of materials, contractor schedules, and even the whims of weather can significantly impact the timeline.

However, with thorough planning and a solid understanding of the process, building an ADU can be a rewarding endeavor that not only adds value to your property but also contributes to the broader goal of creating diverse and sustainable living spaces in our communities.

In the next sections, we will walk through each phase of building an ADU, equipping you with the knowledge and insights needed to embark on this exciting journey.

Understanding the Basics of Accessory Dwelling Units (ADUs)

An Accessory Dwelling Unit (ADU), often referred to as a secondary dwelling unit, is an additional residential building that exists within the grounds of a property zoned for single-family or multifamily use. These versatile structures can be detached from the main house, attached to it, or even be a conversion of an existing space like a garage or basement.

The concept of an ADU is rooted in practicality and flexibility. It offers a unique solution to various living situations. Whether it’s providing a separate living space for family members, such as elderly parents (hence the term ‘granny flat’), or creating a rental opportunity to generate additional income, ADUs have gained popularity for their multifaceted utility.

Defining Characteristics of ADUs:

• Independence: Typically, ADUs are self-contained units that have their entrances, living spaces, kitchens, and bathrooms, ensuring complete functional independence from the primary residence.
• Size: ADUs are generally smaller than the main residence on the property. Their sizes are also regulated by local zoning laws, which define maximum allowable sizes.
• Location: They can be built as stand-alone structures (detached ADUs), as a part of the existing home (attached ADUs), or through the conversion of existing space within the main residence (internal ADUs).

The Advantages of ADUs:

• Affordable Housing: ADUs offer a more affordable housing option in areas where rents and property prices are high.
• Flexibility: They can adapt to the changing needs of a family, such as providing space for aging parents, and grown children, or as a home office.
• Increased Property Value: Properties with ADUs often see an increase in market value due to their added utility and potential rental income.

Regulatory Landscape: The construction and use of ADUs are subject to local building codes, zoning regulations, and sometimes, neighborhood covenants. In cities like Los Angeles, the laws have evolved to be more ADU-friendly, recognizing their potential in addressing housing shortages. Understanding ADUs is about recognizing their role not just as a physical structure, but as a flexible and innovative housing solution in today’s dynamic urban landscapes. They represent a shift towards more versatile, sustainable, and community-oriented living spaces.

The Pre-Construction Phase: Planning and Permits

Before a single shovel hits the ground, the journey of building an Accessory Dwelling Unit (ADU) begins with meticulous planning and obtaining the necessary permits.

This pre-construction phase is crucial in setting the foundation for a successful project.

Researching Local Regulations and Zoning Requirements: The first step in planning an ADU is to understand the local zoning laws and building codes that apply to your property.

Each city or county has specific regulations governing the construction of ADUs, including size limits, placement on the lot, parking requirements, and design standards.

For instance, in Los Angeles, recent changes to state laws have made it easier to add ADUs, but local guidelines still apply.

Familiarizing yourself with these rules ensures your ADU project is compliant and avoids potential legal issues.

Hiring an Architect or Designer: Once you have a clear understanding of the regulatory landscape, the next step is to bring on board a skilled architect or designer.

This professional will help translate your vision into a tangible plan, ensuring the design not only meets your needs but also adheres to local building codes and zoning regulations.

They will also assist in maximizing the use of space and ensuring that the ADU integrates well with your existing property.

Obtaining Necessary Permits and Approvals: With plans in hand, the next crucial step is obtaining the required permits from local authorities.

This typically involves submitting your ADU plans for review, ensuring they comply with building safety standards, and sometimes even undergoing a public hearing process.

The complexity of obtaining permits can vary greatly depending on your location and the specifics of your project. This step can be time-consuming but is vital for the legality and safety of your ADU.

This phase is characterized by diligent research, careful planning, and close collaboration with local authorities and professionals. It sets the tone for the rest of the project and is integral to ensuring that your ADU is built efficiently, legally, and safely.

The Construction Phase: Breaking Ground and Building the ADU

Once all the planning and permits are in place, the construction phase of your Accessory Dwelling Unit (ADU) begins.

This phase is where your ADU starts to take physical shape, transforming from plans and permits to a tangible structure.

Clearing the Construction Site and Preparing the Foundation: The first step is site preparation. This involves clearing the designated area, ensuring it is level, and then laying down the foundation.

The type of foundation required—be it a slab, crawlspace, or basement—depends on the ADU design and local soil conditions.

This stage is crucial as a solid foundation ensures the stability and longevity of the ADU.

Framing the Structure and Installing External Finishes: With the foundation set, the next step is framing. This is where the ADU begins to take shape, with the erection of walls, roof structures, and the installation of windows and doors.

Following this, external finishes such as siding, roofing, and exterior painting are completed. These not only define the aesthetic appeal of the ADU but also protect it from the elements.

Electrical, Plumbing, and HVAC Installation: Once the shell of the ADU is up, the focus shifts to internal systems. This includes the installation of electrical wiring, plumbing systems, and heating, ventilation, and air conditioning (HVAC) units.

These are essential for making the ADU a comfortable, functional living space. Proper installation at this stage is critical for the safety and efficiency of the ADU.

Interior Finishes: The final construction stage involves the interior finishes. This includes flooring, interior painting, cabinetry, and fixtures.

These finishes not only make the space livable but also allow for customization to match the homeowner’s preferences and the overall style of the primary residence. Throughout the construction phase, it’s important to maintain open communication with your contractor and regularly monitor progress.

Timelines can vary based on the size and complexity of the ADU, availability of materials, and other external factors such as weather conditions. However, with diligent management, this phase transforms your ADU from a concept into a reality.

The Post-Construction Phase: Inspections and Final Touches

After the construction of an Accessory Dwelling Unit (ADU) is complete, the project enters its final stage, known as the post-construction phase.

This phase ensures that the ADU meets all the required standards and is ready for occupancy.

Scheduling Inspections at Various Stages of Construction: Throughout the construction process, various inspections are scheduled to ensure compliance with building codes and safety standards.

These inspections, conducted by local building officials, typically occur at several critical stages: post-foundation laying, pre-drywall, pre-final, and final completion. The aim is to catch and rectify any issues before moving to the next phase of construction.

Making Necessary Adjustments or Corrections: Based on the inspection results, there may be adjustments or corrections needed. This could range from minor fixes to more significant alterations. Addressing these issues promptly is crucial for the integrity of the ADU and for obtaining the final approval.

Furnishing the Space and Completing Landscaping Work: Once the ADU passes all inspections, the next step is to furnish the interior and complete any exterior landscaping work. This is where the ADU truly transforms into a livable and inviting space. Furnishing and landscaping are often guided by the homeowner’s aesthetic preferences and the ADU’s intended use.

Obtaining the Certificate of Occupancy: The final step is obtaining a Certificate of Occupancy from local authorities. This certificate is issued after the final inspection and signifies that the ADU is safe and compliant with all regulations, thereby legally permitting occupancy. It’s a crucial document, especially if the ADU is intended for rental purposes.

The post-construction phase is a critical time where attention to detail and adherence to regulations come into play, ensuring the ADU is not just built, but built right and ready for its new occupants.

Factors That Influence the Timeline of Building an ADU

Constructing an Accessory Dwelling Unit (ADU) is a significant project, and its timeline can be influenced by several key factors. Understanding these factors helps in setting realistic expectations and planning effectively for your ADU project.

Size and Complexity of the ADU: The dimensions and design complexity of the ADU play a major role in determining the construction timeline. Larger or more complex designs with custom features or unique architectural elements naturally require more time to build than smaller, simpler units. The complexity not only affects the construction phase but also the planning and design stages.

Availability of Construction Materials: The availability or scarcity of construction materials can significantly impact the timeline. Supply chain disruptions or high demand for certain materials can lead to delays. Choosing readily available materials or having flexibility in material selection can help mitigate these delays.

Contractor’s Schedule: The schedule and availability of your contractor and their crew are crucial. A busy contractor may have multiple projects in line, which could affect the start date or the pace of your ADU project. Clear communication and early booking can ensure your project gets the attention it needs within your desired timeframe.

Weather Conditions: Weather plays an unpredictable yet significant role in construction timelines. Adverse weather conditions like heavy rain, snow, or extreme temperatures can halt construction activities, especially during the site preparation and framing stages.

Planning construction during favorable weather seasons can help reduce weather-related delays. Each of these factors can influence the duration it takes to complete an ADU, and they often interplay with each other.

Being aware of these aspects and incorporating buffer time for unforeseen delays can lead to a smoother construction process and help in achieving your project goals on time.