What are the main cost differences between detached, attached, and garage conversion ADUs?

Detached ADUs are typically the most expensive due to separate construction costs. Attached ADUs can be less costly as they utilize existing structures. Garage conversions are usually the most affordable option.

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Types of ADUs

March 28, 2024

13 min read

Understanding the diverse array of Accessory Dwelling Units (ADUs), including attached ADUs, detached ADUs, and junior ADUs, is paramount whether you’re considering creating a welcoming sanctuary for guests or delving into the rental market.

Modern detached ADU with patio furniture in a landscaped backyard

Introduction

Diving into the world of Accessory Dwelling Units (ADUs) can unlock new potential for your property, offering a versatile solution to meet the ever-growing need for space, privacy, and additional income. Whether creating a cozy retreat for guests, carving out a productive home office, or tapping into the lucrative rental market, understanding the different types of ADUs—detached ADU, attached ADU, ADU garage conversion, room addition, and junior ADU—is crucial. Each option presents unique benefits and considerations, shaping how you expand your living area to meet your specific desires and challenges. Let’s navigate these options together, providing the insights needed to transform your property into a space that does more for you.

Types of ADUs at a Glance

Understanding the various types of ADUs is crucial for homeowners seeking to expand their living space, with each type offering specific advantages suited to different needs and property configurations. Detached ADUs provide maximum privacy and design flexibility but require higher costs and longer construction times. Attached and garage conversion ADUs balance cost-efficiency and convenience with moderate privacy and potential for increased property value. Junior ADUs (JADUs) provide a low-cost solution within the main house’s footprint, ideal for minimal alterations. By grasping the unique benefits and considerations of each ADU type, homeowners can make informed decisions aligned with their goals, whether it’s generating additional income, accommodating family members, or boosting property value.

Factors	Detached ADUs	Attached ADUs	Garage Conversion ADUs	Junior ADUs (JADUs)
Cost	High due to separate construction	Moderate, using existing structures	Lowest, minimal structural changes	Low, minimal adjustments needed
Privacy	structure	Moderate, shared walls with main house	Low to moderate, depends on design	Lowest, within main home
Construction Time	Longer, standalone project	Moderate, depends on existing home complexity	Shortest, uses existing space	Short, less construction required
Rental Potential	High, desirable standalone unit	Moderate, appeal varies	Moderate, depends on conversion quality	Low, smaller and within main house
Design Flexibility	High, blank canvas	Moderate, limited by existing home	Low, constrained by garage layout	Low, limited by existing space
Impact on Property Value	High, significant addition	Moderate to high, enhances usability	Moderate, improves functionality	Moderate, adds versatility

Detached ADUs

Detached ADUs are separated from your primary residence, offering unparalleled privacy and creative design opportunities. They are ideal if you’re aiming to establish an entirely independent living area or a rental unit.

Pros

Ensures privacy and independence.

Significantly boosts property value.

Allows for flexible design choices.

Cons

Higher construction cost.

Longer construction timeline.

Best Use Cases

Generating rental income.

Providing independent living spaces for family.

Attached ADUs

Attached ADUs expand on your current home. They share a wall with your main house but feature a separate entrance, compromising accessibility and privacy.

Pros

More cost-effective than detached units

Offers moderate privacy

Simplifies utility management and access

Cons

Limited design flexibility

Potential privacy concerns

Best Use Cases

Expanding family living areas

Establishing home offices or studios

Garage Conversion ADUs

Garage ADU conversions repurpose existing structures into livable spaces, providing an efficient and economical way to enhance your home’s functionality. These conversions are particularly appealing for their lower costs and rapid completion times.

Pros

Most cost-efficient option.

Quickest to complete.

Minimal construction impact.

Cons

Limited by the existing garage’s layout.

May require alternative parking solutions.

Best Use Cases

Developing affordable rental units.

Creating distinct workspaces.

Room Additions

Room additions provide a flexible solution to add specific, functional spaces to your home, from enlarging your living room to adding new bedrooms or custom spaces like home offices.

Pros

Seamlessly integrates with the existing design.

Enhances property value.

Offers design and utility flexibility.

Cons

Can be costly.

Requires significant construction time.

May face permitting and zoning challenges.

Best Use Cases

Adding bedrooms for a growing family.

Customizing spaces for work, fitness, or entertainment.

Junior ADUs (JADUs)

Junior ADUs fit within the blueprint of your main house, usually transforming a bedroom or similar area into a compact, independent unit.

Pros

Requires minimal construction.

Easily accessible amenities.

Cons

Limited size and scope.

Offers the least privacy.

Best Use Cases

Economical living space expansion.

Accommodating a single occupant or student.

Summary

With a deeper understanding of the various types of ADUs and their unique benefits, you’re now ready to transform your property into a more versatile and value-added space. Whether it’s the privacy and independence offered by a detached ADU, the cost-efficiency of a garage ADU conversion, or the minimalistic charm of a junior ADU, each option presents a tailored solution to enhance your living space.

At Better Place Design & Build, our one-stop-shop approach simplifies decision-making, ensuring you find the perfect ADU type that aligns with your needs and aspirations. Serving all of San Diego County, from Bonita to Poway, we are the leading San Diego ADU builders ready to bring your next project to life. Our expertise in creating customized ADUs and a deep understanding of local regulations and design trends position us as the ideal partner in your ADU development journey.

FAQs

An Accessory Dwelling Unit (ADU) is a secondary housing unit on a single-family residential lot. Building one can offer additional living space, house family members, generate rental income, and increase property value.

Detached ADUs are the most expensive and require new construction. Conversely, attached ADUs leverage your home’s existing structure to lower costs, and garage conversions are the most budget-friendly, transforming unused space into valuable living areas.

In California, there are several types of ADUs, including Attached ADUs, Detached ADUs, Garage Conversion ADUs, Above-Garage ADUs, and Junior ADUs (JADUs). Each type offers various benefits depending on homeowner needs and property constraints.

ADUs are also known as granny flats, in-law units, secondary dwelling units, backyard cottages, and laneway houses. These names can vary regionally but generally describe the same concept of an additional, self-contained living space on the same grounds as a main residence.

An attached ADU is connected to the main residence, sharing at least one wall. It is typically less expensive to build due to shared utilities. A detached ADU is a standalone structure, offering more privacy and often requiring more extensive construction and utility setup.

An attached ADU is a self-contained unit with its own kitchen, bathroom, and entrance, designed as a separate living space. An addition extends the existing structure of the main house, such as adding extra rooms, and does not function as an independent dwelling.

Generally, it can be cheaper to convert existing space into an ADU, especially with garage conversions. Building an addition often involves more extensive construction and integration with the existing home, which can increase costs.

Yes, adding an ADU can be a good investment. It can increase property value, provide rental income, and offer flexible living arrangements for family or tenants. The return on investment depends on local real estate market conditions and the quality of the ADU.

One drawback of an ADU is the potential for increased property taxes, as the addition of a dwelling unit can raise the property’s assessed value. Additionally, managing tenants or rental agreements can add complexity for homeowners.

This depends on individual circumstances. Building an ADU can be more cost-effective and increase the value of an existing property. Buying a house is typically more straightforward but involves the full process of purchasing real estate, which might be more expensive overall.

The added value can vary significantly but generally ranges from 20% to 30% of the home’s value, depending on the ADU’s size, quality, and location. In high-demand rental markets, the increase can be even greater.

Privacy considerations vary by ADU type. Detached ADUs offer the most privacy from the main house, while attached ADUs and garage conversions may require additional measures like soundproofing and separate entrances to enhance privacy for both the ADU occupants and the homeowners.

Determining the feasibility of an attached ADU involves assessing factors such as available space, local regulations, budget, and intended use. Better Place Design & Build offers comprehensive consultations to evaluate your property and discuss your goals, providing expert guidance on whether an attached ADU is the right choice for you.

Zoning and building regulations for detached ADUs vary depending on the location and local ordinances. It’s essential to consult with Better Place Design & Build and local authorities to understand the specific requirements and permits needed for building a detached ADU on your property.