Everything You Need to Know About Building an ADU Unit from A-to-Z
Cottage has worked with hundreds of homeowners across 40+ municipalities in the San Francisco Bay Area and Los Angeles Area for their ADUs. We’ve experienced all the factors that make some properties great and others more challenging.
Here is the definitive list of resources for homeowners getting started on their ADU journey. We hope our expertise in evaluating, designing, permitting, and building backyard Cottages will help bring more affordable housing across the state and beyond.
Our guide can help you along in your ADU journey, and our team is always here to provide expert ADU advice based on real ADU experience. Click the "Get Started" button on the top right corner of our website 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:
- What is an ADU (Accessory Dwelling Unit)? —ADUs go by many names— casita, granny flat, in-law unit, coach house, and more. We define ADUs based on their legal definition and building code requirements in this short post.
- What are the Different Types of ADUs? — Understanding the different ADU options—a backyard cottage, attached ADU, garage conversion ADU, or interior house conversion ADU—is key to understanding what’s possible on your property.
- Where Can I Build My Accessory Dwelling Unit? — From visiting hundreds of homes across the San Francisco Bay Area and greater Los Angeles region, we share how we determine the best spot for your ADU—both for permitting ease and cost.
- Is My Property Eligible for an ADU? — Specific city eligibility requirements can be a headache! We cover the four most important criteria that cities use that you don’t want to miss: setbacks, maximum size and height, parking, and the number of ADUs you can build.
- City-by-City ADU Regulations — Cottage has compiled the city-by-city ADU regulations so you don’t have to. Click through this link to learn more about the specific requirements in your city. Don’t see your city? Book a time to speak with us, and we can still walk you through your city’s eligibility step-by-step.
- Ready to Start Your ADU Project? — 5 key things to do NOW for a smooth build for your ADU unit.
Financing & Costs:
Cost can be one of the biggest challenges for your ADU. With every project having unique site conditions, design, and finishes, the Cottage team has broken things down 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 are 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 immediately generates 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, generate retirement or passive income, or simply as a space you’ll coexist with. Here’s what we’ve learned in designing hundreds of ADUs to make yours beautiful, complementary, affordable, and functional.
- 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. Cottage’s Head of Architecture Anamika Goyal, shares a few tricks to maximize your ADU’s value and minimize costs.
- Designing the Best ADU Exteriors and Interiors — Homeowners love choosing their ADU’s finishes and visual details—we see it with every homeowner we work with! Read this article to learn some great finishing touches that will make your friends think you moonlight as an interior designer—all for an affordable cost.
- ADU Consultants: What You'll Need for Your Project — Designing, planning, permitting, and building a new ADU takes a network consultants and trusted partners. Cottage does this for you and unlocks volume discounts in the process.
You’re ready to talk nuts and bolts and build your ADU. Cottage has talked to hundreds of local General Contractors—and hand-picked the best for quality and value to join our exclusive contractor network—and have learned how to identify who to trust with your project quality, cost, and timeline.
- How to Choose the Right ADU Builder — In this can’t-miss post, Cottage’s Contractor Partnerships lead, Hillary Scott, walks you through how to vet your contractor and make the right choice for your ADU.
- 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? We outline the pros and cons of all the different ADU companies out there. The key points to consider? Construction durability, customizability, and cost.
- The ADU Building Timeline — What are key milestones in permitting and construction for your ADU project? The Cottage team covers the key steps to your ADU construction.
Cottage’s A-to-Z ADU Approach:
What makes Cottage the easiest, highest quality, and most affordable 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 brings transparency and clarity to an industry that desperately needs it. We give up-front estimates for your ADU before you spend a penny on the project, a professional in-house design experience, and special attention from a Cottage-vetted General Contractor. All this with market-leading and affordable prices for your custom, stick-built ADU.
- 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!
- Cottage Completed Project: 2 Bedroom, 741 sq. ft. Detached ADU — We recently finished construction on a rental-optimized ADU with 2 bedrooms in San Jose, California. Learn more about how we fit 2 bedrooms, a bathroom, a kitchen, and an open floor plan living area into a great design while keeping costs low for an ROI-minded property investor.
- Cottage Completed Project: 227 sq. ft. Attached Studio ADU Unit — This 227 sq ft ADU in Palo Alto, California just found its first tenant for $2,500 / month! See some great photos of the home and learn how we squeezed every inch out of a small space.