ADU Plans, Floor Plans & House Designs

What is an accessory dwelling unit (ADU)?

An accessory dwelling unit (ADU) is a smaller, secondary home on the same property as a main house. They’re often used to house guests, aging family members, or long-term renters, offering a flexible way to add livable square footage without expanding the main structure. Many include their own kitchen, bathroom, and living space.

What are the most popular ADU layouts?

ADU plans come in a wide range of layouts, from efficient studios to well-appointed backyard homes, each thoughtfully designed to suit your lot, your needs, and the way you live.

• Studio Plan: Compact and efficient for guests, offices, or short stays.

• 1 Bedroom Plan: A straightforward layout with a little more privacy.

• 2-3 Bedroom Plan: A flexible option for families, renters, or multigenerational living.

• Garage Apartment Plan: A small home/apartment built next to or above a garage.

• Pool House Plan: Often used for entertaining, lounging, or guest overflow.

Can I build an ADU on my property?

Building an ADU plan on your property depends on when you’re building, what the local zoning allows, and how big the lot is. Setbacks, permits, utilities, and neighborhood restrictions can all shape what’s possible.

To get a better idea of what's possible in your area and on your specific lot, we recommend talking to your contractor or local building authority.

What are the typical cost considerations for building an ADU?

The cost of building an ADU plan can vary widely. Cost depends on a variety factors, like size, design complexity, location, and level of finish. No two builds are exactly alike, but these core elements consistently influence the overall investment:

• Materials and finishes: From flooring and countertops to cabinetry and fixtures, your selections play a major role in the final price. Elevated, high-end finishes can quickly push costs upward.

• Location: Where you build matters. Regional labor rates, cost of living, and local building requirements all impact pricing. Permitting processes and codes can also affect both timeline and budget, making early collaboration with a builder essential.

• Home size and layout: Larger plans typically carry a higher total cost, though they often benefit from a lower cost per square foot compared to smaller, more compact designs.

• Labor and construction complexity: Labor costs fluctuate by market and are closely tied to the intricacy of the build. Detailed architectural features or challenging site conditions can increase both construction time and overall expense.

To get a better idea of what a particular house plan will cost to build in your area, we recommend discussing your plan with your builder. You can also order a cost to build report for any house design on our site. Just click the Get Cost to Build Report button on the plan detail page. Have more questions about cost to build? Check out our Cost to Build FAQ.

How long does it take to build an ADU?

The timeline for building an ADU plan depends on the size and complexity of the design, your city’s permitting process, and the specifics of your lot. Weather and contractor availability also play a role.

What are the benefits of building an ADU?

Building an ADU is a smart way to add flexibility, income potential, and long-term value to a property. Whether it’s used for guests, family, a home office, or rental income, it creates extra space that can grow and change with your needs.

Can I customize an ADU floor plan?

You sure can! Whether you're fine-tuning a plan you already love or starting fresh, our team is here to bring your vision to life. We offer a wide range of customization options, such as:

• Adjusting window and door placement
• Modifying ceiling heights
• Expanding or reducing overall square footage
• Editing the footprint
• Reworking room layouts for better flow
• Changing garage size or capacity
• Enhancing outdoor living spaces, like porches, patios, or decks
• Selecting an alternate framing or foundation option

Have more questions about house plan customizations? Check out our Modification Guide, or give us a call.

What financing options are available for ADUs?

Once you've picked your ADU plan, check with your bank or local lender about financing options. Your bank might have home equity loans or construction loans that could work. Some regions may have ADU grant programs, so ask about local options too. Before closing, make sure you have permits and builder plans ready in case the lenders require both.

Can an ADU be used as a rental property?

In general, yes. And renting out an ADU can be a smart way to generate steady income and offset your mortgage. That said, be sure to check local regulations before starting your build.

What are the best ADU plans for multigenerational living?

Well-designed ADU plans for multigenerational living prioritize separation without sacrificing connection. Look for designs with flexible rooms and thoughtful essentials, like private entrances, full kitchens (or streamlined kitchenettes), generous walk-in closets, and aging-in-place features (e.g. minimal stairs).

You should also check out our collection of multigenerational house plans in which you'll discover home designs with in-law suites and in-law apartments.

How can I maximize space in a small ADU?

Small doesn’t have to mean cramped. Maximize every inch of your small ADU plan with a smart open layout that keeps the space feeling light, connected, and easy to live in. Thoughtful indoor-outdoor flow and vaulted ceilings can also make the home feel bigger and brighter without increasing heated square footage. To minimize clutter, look for designs with clever built-ins, hidden storage, and/or multipurpose rooms.

How large can an ADU be?

ADU sizing depends on your lot, your primary home, and your local regulations. Our ADU plans span a range of footprints, from compact studio-style layouts to more spacious one-bedroom (or larger) designs, giving you the flexibility to build what fits your lifestyle and your land.

What’s included in my ADU floor plan package?

Most ADU plans include a foundation plan, floor plans, a roof plan, and exterior elevations. Many also come with building sections, electrical plans, and construction details.

Check the plan details online to see exactly what’s included, or contact us if you have questions.

Can I use an ADU floor plan to build a tiny, primary residence?

Absolutely! An ADU floor plan is a well-designed small home, and in many areas, it can be used as a tiny primary residence. The key is how your local zoning and building department labels it on paper, so before you build, double-check your local rules on minimum house size, setbacks, and whether it will be permitted as a main dwelling on your lot.

Have More Questions?

Discover more answers to frequently asked questions on the main Houseplans FAQ page.