Accessory Dwelling Units Plans

How Much Does It Cost?

Let’s be real—one of the first questions on everyone’s mind when planning a custom ADU is: How much will it cost? And the honest answer is: it depends.

Every ADU is unique, and the design cost can vary depending on the size, complexity, and specifics of your property. But here’s the good news—we make pricing as transparent and predictable as possible.

Most architects charge between 4–7% of your total construction budget for design services. At QuickenPlans, we take a different approach: we work on a flat-fee basis. That means no surprises, no percentage-based markups—just clear pricing that reflects the scope of your project.

What Affects the Cost?

Several factors influence the overall design and engineering cost of your ADU:

• Location: Local regulations, permitting requirements, and jurisdictional nuances can all affect design scope and cost.

• Size: Larger ADUs require more detailed work, which naturally increases design time and complexity.

• Project Type:

- Stand-Alone ADUs usually involve more design work than conversions or attachments.

- Attached ADUs need to integrate seamlessly with the existing structure, which can present structural challenges.

- Garage Conversions may appear simple but often involve major upgrades to framing, utilities, and foundations.

• Number of Stories: Two-story units add complexity due to additional structural and code compliance requirements.

• Construction Methods: Unconventional or high-efficiency construction techniques can add to the design effort.

• Terrain: Sloped or uneven lots may require more engineering and site planning.

What’s the Price Range?

Here’s a general breakdown of what to expect:

• Smaller, simpler projects, like garage conversions or modest single-story ADUs — $5,000–$10,000.

• Larger or more complex ADUs, such as multi-story, detached structures, or those with custom features and challenging site conditions — $15,000–$20,000+

These ranges reflect full-service building design and structural engineering, including what’s needed to get your plans permit-ready (except site studies like survey, etc., civil and MEP engineering).

Getting an Accurate Estimate

Every property and project is different. That’s why the best way to get a clear cost estimate is to book a consultation. We’ll review your goals, site details, and timeline—and provide a tailored quote that reflects the real scope of your project.

Timeline & What You’ll Get

When planning your custom ADU, it helps to know what to expect—both in terms of how long it’ll take and what’s included. At QuickenPlans, we strike the right balance between speed and quality, delivering thoughtful, permit-ready plans without unnecessary delays.

How Long Does It Take?

The design process is a collaborative effort. While we keep things moving on our end, timely feedback and decisions on yours play a big role in staying on schedule. Here’s a general idea of the timeline:

• First Concept Design:

After your design kick-off meeting, we’ll deliver your first concept iteration within 10–15 business days. This is the first time you’ll see your vision start to take shape.

• Full Design & Engineering:

From initial consultation to final deliverables, most projects are completed in 2–4 months—as long as there’s steady communication and prompt feedback throughout. Delays in approvals or decision-making can naturally extend the timeline.

What’s Included?

Deliverables may vary slightly based on your local regulations, but here’s what’s typically included in a full custom ADU plan set:

• Site Plan – A layout showing the ADU’s placement in relation to property lines and existing structures.

• Floor Plan – Interior layout with room dimensions, doors, windows, and fixtures.

• Elevations – Exterior views from all sides, showing windows, rooflines, and finish details.

• Sections – Cross-sectional views that show how different levels and spaces relate.

• Roof Plan – Roof design with slopes, materials, and any skylights or special features.

• Basic MEP Layout – Placement of visible Mechanical, Electrical, and Plumbing fixtures.

• Construction Details – Key details like wall assemblies, connections, etc.

• Structural Drawings & Calculations – Foundation, framing, and structural specs, prepared and stamped by one of our in-house licensed engineers, ready for review by building officials.

• Energy Compliance Report – Required in many areas, this ensures your ADU meets current energy efficiency standards.

Let’s Make It Happen

We keep the process clear, collaborative, and on schedule—so your plans are ready when you need them. With the right communication and a bit of teamwork, we’ll get your ADU design across the finish line, just the way you envisioned.