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The Complete Guide to Creating Your Backyard ADU

Save this guide for instant access to everything you need to know about building a backyard home, or Accessory Dwelling Unit (ADU). Get Cottage's expert advice based on real ADU experience

May 22, 2024

Everything You Need to Know About Building an ADU

Cottage has helped hundreds of homeowners in 60+ municipalities across the West Coast create ADUs they love. We've experienced the ins and outs of the ADU journey - and we're excited to share what we know with you.

Here is the definitive list of resources for homeowners getting started on their ADU project. We hope our expertise in each step of the process - feasibility, design, permitting, and construction - will help you as you embark on your own journey to create your dream backyard home.

In addition to this guide, our team is always here to provide expert ADU advice based on our experience. Click the "Get Started" button in the top right of your screen to schedule a free 30-minute consultation and estimate today.

ADU Property Eligibility:

The first step is figuring out whether you can build an ADU on your lot. Here are articles that cover the important basics:

Financing & Costs:

Cost can be one of the biggest challenges for your ADU. With every project having unique site conditions, design, and finishes, we share a breakdown of ADU costs for you.

  • What are the Soft Costs of Building An ADU? (Design, Consultants, Permitting) — Soft costs are the non-construction costs of your ADU project. These required consultants and engineers, and permitting are key for your project. This is especially true when most general contractors leave these costs out of their estimates.
  • What are the Hard Costs of Building An ADU? (Site Prep & Construction) — Hard costs refer to the construction costs of your ADU—think labor and materials. See behind the scenes at what general contractors are thinking when they price your ADU project.
  • What ADU Financing Options Are There? — Investing in ADUs boosts your property value and can generate a new stream of passive rental income. Read to learn about the common ADU financing options out there to unlock your property’s fullest potential.


Cottage ADUs are designed and built to last. They’ll be on your property for a lifetime—a space to build family memories, age in-place, generate passive income, or whatever your use case is. Drawing from our experience designing hundreds of ADUs, here's what to know to achieve a beautiful, functional design:

  • How Do I Choose the Right ADU Size & Floor Plan? — Our first step with every homeowner is understanding their motivations and needs. Read this article to see floor plans that reflect the most common use cases for ADUs.
  • How to Choose the Best ADU Designer and Architect? — Whether you work with Cottage or DIY your ADU, your designer or architect will be a key partner in your ADU journey. Our advice: find someone who specializes in ADUs, has a sharp understanding of construction costs, knows the local permitting requirements, and is responsive to you and your property’s needs. Read on to learn more.
  • Designing For ADU Value and Quality — Surprisingly, many architects don’t have a firm grasp of what drives costs in building an ADU. Small design decisions can yield huge savings...or costs. Our team shares a few tricks to maximize your ADU’s value and keep costs down.
  • Designing the Best ADU Exteriors and Interiors — Choosing your ADU’s finishes and visual details really brings your new space to life. Read this article to learn some tips on selecting your finishes to match your style, use case, and budget.
  • ADU Consultants: What You'll Need for Your Project — Getting your ADU across the finish line takes a network consultants and trusted partners. Learn what experts you'll need to work with, and how Cottage connects you to vetted professionals and unlocks negotiated pricing to get you the best value.


You’re ready to talk nuts and bolts and build your ADU. Good news: Cottage has vetted hundreds of local General Contractors and hand-picked the best for quality and value to join our exclusive Builder Network. Here's what we've learned.

  • How to Choose the Right ADU Builder — In this can’t-miss post, we walk you through how to vet your contractor and make the right choice for your ADU project.
  • The Custom ADU vs. Prefab ADU vs. Modular ADU Trade-Offs — We’ve been there—you search about ADUs once, and now your social feed is filled with different ADU companies out there. How do you compare them? In this post, we outline the pros and cons of all your ADU options. The key points to consider? Construction durability, customizability, and cost.
  • The ADU Building Timeline — We highlight the key milestones in permitting and construction for your ADU project, and what timelines can look like.

With Cottage, Bring Your Entire ADU Project Under One Roof:

What makes Cottage the smartest, best-value way to build your ADU? Learn more in the following posts about how we work, who we are, and the completed ADUs we’re proud of.

  • Cottage: How it Works — Cottage can help you through every step of the ADU journey, from feasibility, to design, permitting, and construction. At each stage, we offer best-in-market value and connect you with highly vetted professionals. Plus, with our pay as you go structure, you get to choose the scope for your project at your own pace.
  • Cottage: About Us — We’re a team of California natives who are passionate about housing affordability and working with homeowners like yourself. Meet the team!
  • Completed Project: 1 bed, 1 bath, 373 sq. ft. ADU for hosting and working — This one's a stunner. Learn how we partnered with these homeowners to bring their dream ADU to life: a unit for housing guests, hosting get-togethers, and working from home.
  • Completed Project: 227 sq. ft. attached ADU for rental income — This 227 sq. ft. ADU in Palo Alto, California just found its first tenant for $2,500 / month! See some great photos of the unit and learn how we squeezed every inch out of a small space.

Cottage: Custom ADUs Made Simple

We hope this guide can be a helpful resource for you on your ADU journey. We're excited for you - and we're here to help you through each step of the way. Get in touch today for a free consultation and estimate!

Have a question or ready to get started? Click the "Get Started" button on the top right corner of the screen to schedule a free consultation and estimate.