3 Ways to

Build an ADU

We outline the 3 primary ways how to build an ADU including, Design-Build, Prefab ADUs, and, Pre-Designed Plans by an Architect & Built by a GC, the Pros & Cons of each method

To date, several methods have gained popularity in the decision-making process for building an ADU, among which custom home builders stand out as a prevalent but not necessarily the most advantageous choice, particularly if you prioritize cost-savings, time efficiency, and superior design.

Allow me to outline the three primary options for constructing an ADU:

  • Design-Build ADU Companies

  • Prefabricated ADUs (Built Off-Site, Assembled On-Site)

  • Architect-Designed ADU Plans with GC Collaboration

Design-Build ADU Companies

Cookie Cutter & the Inherent Conflict of Interest

These businesses typically prioritize volume and sales, which makes them proficient builders. However, they are not deviating from a proven formula. They will design a home for your lot and then construct it using their own established procedures instead of breaking the mold to offer more innovative design or build techniques. Typically, a design-build company starts with a template of a home they already built or a standardized plan they bought online, and they make customizations to align with your preferences

Their material selection often comes from bulk purchases stored in warehouses, contributing to the uniform appearance of many American streets and cookie cutter aesthetic of American homes. Because they do design ADUs specifically for individual clients, the process is extensive, and since you’re opting for a comprehensive solution that includes both design and build, the pricing tends to be opaque and generally more expensive.

A Closer Look

Although design-build firms are not composed of expert designers—often, their in-house designers lack formal architecture or interior design education—they still charge a hefty design fee. This model has inherent conflicts of interest; the same entity is responsible for both design and construction. Such an integrated approach may inadvertently prioritize cost savings for the company during construction, which can compromise the design’s integrity.

Their material selection often comes from bulk purchases stored in warehouses, contributing to the uniform appearance of many American streets and cookie cutter appearance of American homes.

Limited Cost Transparency

 In contrast to traditional project delivery methods where multiple contractors bid on the construction phase—encouraging competition and potential cost savings—the design-build model often works with a select group of preferred subcontractors. This limitation can lead to less competitive bidding and potentially higher construction costs.

Despite these obvious hindrances, the primary advantage of design-build is by providing a single point of contact for clients, design-build companies can offer greater efficiency and a single source of accountability.

Prefabricated ADUs (Built Off-Site, Assembled On-Site)

Balancing Time with Cost

Prefab Accessory Dwelling Units (ADUs) can be a costlier option upfront, considering the full spectrum of construction steps. However, their main advantage lies in the significant reduction of construction time—often by several months. It’s important to note that even with prefab ADUs, engaging a licensed contractor is still necessary for site preparation, laying the foundation, managing utility hookups, and navigating the permitting process.

Permitting Challenges and Lack of Willing GCs

 These units utilize non-traditional construction techniques, which may not yet be fully endorsed by building regulators, potentially leading to prolonged permitting review times.

Additionally, the unfamiliarity with prefab assembly can make it challenging to find contractors willing to undertake such projects.

Even with prefab ADUs, engaging a licensed contractor is necessary for site preparation, laying the foundation, managing utility hookups, and navigating the permitting process.

The Future of Prefab Construction

Despite these hurdles, the resurgence of interest in prefab construction is exciting. It represents a forward-thinking approach to building, promising efficiency and innovation. As the industry evolves, we anticipate further exploration and refinement of this construction method.

Architect-Designed ADU Plans with GC Collaboration

An Additional Step

To be transparent: the perspective we’re sharing stems from our position as an architecture firm. However, there’s a deliberate rationale behind our company’s structure, which we’ll delve into as you continue reading.

Choosing architect-designed ADU plans with GC collaboration is a strategic decision for those who value design and longevity in building. Architects prioritize the long-term impact of design choices, aiming to future-proof homes by integrating adaptable features for evolving needs and technologies. This foresight often prevents architects from adopting a design-build model due to potential conflicts of interest.

The Architect’s Edge

Architects are adept at crafting functional, visually appealing, and innovative spaces. They are in tune with human requirements and excel at converting these into well-thought-out homes. Unlike builders, who might adhere to a standardized template lacking individuality, architects ensure that each home stands out with its unique character.

Cost Implications & Long-Term Savings

While architects’ fees for custom homes can reach up to 20% of the construction budget, their expertise can result in long-term savings by optimizing space, enhancing energy efficiency, and judiciously selecting materials. However, for pre-designed plans, architects’ fees are considerably lower, often just a few thousand dollars.

Navigating the General Contractor’s Landscape

If you opt for an architect’s pre-designed plan, you may need to find a GC independently, especially if the architect’s network is fully booked. If you don’t have a reputable recommendation from your own friends and family network, this (called a “bid process”) involves interviewing multiple GCs and requesting cost estimates. It should be noted, the bid process only benefits a project in many ways such as competitive pricing, diverse options of GCs, transparency and accountability, negotiation leverage, and risk mitigation, overall, allowing for informed decision-making and increased likelihood of a successful and cost-effective construction project.

For more detailed guidance on selecting a GC, read our FAQ.

An architect shapes the project’s vision, conducts the planning, research building codes, and provide technical and construction expertise. A GC plus Architect collaboration offers a valuable alternative to standard home builders.

Architect plus GC: A Synergistic Partnership

In contrast to the home builder, the architect collaborates with a general contractor to oversee the construction of a custom home designed by the architect. In the case of pre-designed plans, the architect provides complete instructions and technical detail on how the GC should build their designs.

Architects contribute significantly beyond construction. They shape the project’s vision, engage in comprehensive planning, research building codes, and provide technical expertise, ensuring the project’s success.

A collaboration between a GC and an Architect presents a valuable alternative to conventional home builders and design-build firms.

And for those seeking cost transparency and savings as well as well thought-out designs and durability, using architect pre-designed plans are a great choice.


The journey to constructing your Accessory Dwelling Unit is paved with choices that reflect your priorities and vision. Whether you choose the efficient yet costly route of a design-build company, the modern innovation of a prefabricated unit, or the bespoke craftsmanship of an architect-designed ADU in collaboration with a General Contractor, each avenue presents distinct advantages.

Consider what matters most to you: Is it speed, innovation, sustainability, or enduring, top-notch design? Your choice will not only define the physical form of your ADU but also the quality of life it cultivates.

We provide comprehensive ADU plans, fully designed for both exterior and interior, ready for construction. With no need for additional architect involvement, you can seamlessly hand off the plans to your general contractor and witness your project come to life.