ADU 101: All the Basics You Need To Know

Do you want to know what an ADU is? Do you have a question about how to get one built or permitted in your city? Are you interested in learning more about the benefits of housing extra people on your property, but don’t know where to start? An ADU can be a great solution for many situations. This article will cover all the basics that you need to know about ADUs.

What Is An Accessory Dwelling Unit?

Accessory dwelling units are smaller, independent living quarters connected to an existing home. They’re also known as granny flats or in-law apartments because they were originally built for parents to live with their children and provide additional income to the family through rental agreements. 

Today’s accessory dwelling unit is more likely intended to serve another purpose but still offers extra space that can be used by a renter or owner themselves.

The most common types of ADUs are garage apartments and backyard cottages, but there are other options out there too!

Why Do People Choose To Build Accessory Dwelling Units?

An ADU can be an affordable way to own a home. People love living close together and sharing communal spaces like patios and gardens but sometimes privacy is preferred too. An Accessory Dwelling Unit allows for both! You can make your small backyard garden into a communal spot for friends and family to gather while still having an entire home off to the side where you can retreat after hosting or entertaining.

Why Is The Foundation Important In Building An Accessory Dwelling Unit?

There are many reasons why building a foundation is important, but the most basic one is safety. A good foundation will keep your ADU from shifting to an unsafe position and causing structural issues that can potentially compromise its integrity or even cause it to collapse entirely. 

In addition, you do not want rainwater entering into the unit because of poor drainage around foundations leading to water damage within which could lead to mold growth and other health hazards for occupants living in the accessory dwelling unit space. 

Finally, a solid foundation provides a stable base on which all walls must be built so they remain straight at each corner allowing you to build them square with no sagging over time if done correctly during the construction process.

Why Is It Important To Use Concrete In Building A Foundation For ADUs?

One of the most important components in building an accessory dwelling unit is a concrete foundation. It provides great support and strength to all other materials that will be used when constructing your ADU. Concrete also has many benefits that facilitate its use, such as:

  • It is easy and quick to install and finish
  • It can be very cost-effective due to longevity in usage
  • It allows for watertight construction which makes it durable against weather elements like rain, snow, or wind
  • It reduces moisture build-up on walls by acting as a vapor barrier unlike wood foundations
  • Easily customizable with different types of finishes such as paints, stains, etc.

What Type Of Accessory Dwelling Unit Should You Build?

There are many things you need to think about when deciding what type of accessory dwelling unit would work best for your property. The more complex the design, the higher the cost involved will be – though it may still end up being cheaper than building on entirely new land or even just updating your existing home. Some questions you might ask yourself include: Does my house have enough room in the backyard to add a new unit? Do I have enough space in my garage for an apartment or cottage? Can I make the changes to my property myself, or will it require permits and professional help?

What Are The Different Variations Of Accessory Dwelling Units?

An accessory dwelling unit (ADU) is a one- or two-person housing unit with complete independent living amenities. There are several types of ADUs:

Detached Accessory Dwelling Unit

The unit is not connected to the main house. It has a separate entrance and provides an additional housing option for homeowners. These units come with their own kitchens and bathrooms so they’re great for those looking to rent out rooms or who need extra space without making any major renovations to their existing property.

Attached Accessory Dwelling Unit

This is an accessory dwelling unit that is attached to the primary structure or main house.

Transformed Existing Space

Space on the property of the main house that is converted into an independent living unit. Examples would be the master bedroom, connected garage, storage space, or similar usage, or an additional structure.

Junior Accessory Dwelling Unit

A sort of existing space conversion that is totally contained within an existing or projected single-family dwelling.

What Are Examples Of Accessory Dwelling Units?

Garage apartments (also known as granny flats) are just that – accessory dwelling units that you build into your garage. They’re good options if you don’t want your main house disturbed by noise from tenants living above, but they can also be more expensive than building something smaller like a backyard cottage. 

Garages often need to be insulated and treated with fireproof materials before being turned into livable spaces. 

Granny flats sometimes involve turning part of your yard into a new unit, so it’s important to think about your landscaping and how you’ll manage any trees or other plants on the property.

Backyard cottages are stand-alone units that can be built in their own right without having to disturb your house at all. They’re often smaller than granny flats, but they don’t require more of your yard like an apartment would (which might make them a better option for some people). 

You also won’t need as long of a construction timeline; backyard cottages will usually take only three months from start to finish. The downside is that you do have to get extra permits involved since they aren’t attached directly onto your main home – plus there’s always the chance that someone might not want to rent it.

There are many other kinds of accessory dwelling units, including mother-in-law suites, tiny homes, carriage houses, and more! You can even build a free-standing garage or barn if that makes the most sense for your property. 

It all depends on what you need – but whatever kind it is, an ADU could be just what you’re looking for in order to have extra living space without having to deal with building something larger like a new home.

    Pleasant Hill Remodel Stamped Concrete Project

    What Do I Need To Know About Building An Accessory Dwelling Unit?

    Building an accessory dwelling unit doesn’t mean slapping up some walls inside your garage and calling it good. There’s quite a bit involved when adding this type of housing to your property.

    Here are all the basic things you need to know about building an accessory dwelling unit:


    If this is not permitted in your specific neighborhood, then don’t even bother starting! Check with local authorities before making any plans for this type of housing addition to your home. If it does happen to be allowed there will likely be size limitations and other restrictions that may come into play when figuring out how much room can go towards ADUs on a single property.


    What’s required from where the main house sits? Space needs regulating too so find out right away what accommodations need to be made during the design process of adding space onto existing structures like homes or garages. Some places require twenty feet while others allow for ten.


    Depending on how big your accessory dwelling unit is you may need to provide additional spaces for cars if the main house has limited spots available. If there’s no room in the driveway or road, see about getting one of those tiny little garage structures put up so that tenants have a place to park their vehicles out of sight and out of mind while they reside at your property.


    Before any new construction begins, check with utility companies like electricity providers to ensure everything runs smoothly once walls are erected between existing rooms and newly built areas inside homes or garages already standing on properties all around town. Be prepared for certain things not being allowed unless you set up ahead of time by way of planning permission from local authorities beforehand!

    Can It Be A Source Of Income?

    If you choose to rent your accessory dwelling unit, or ADU as it’s commonly called, the amount of income you receive is taxable and may be subject to capital gains taxes if you sell your home. 

    However, this can make sense for some homeowners who want a steady stream of passive income over time by renting their house instead of selling it when they retire or move on from that location. 

    So yes—an accessory dwelling unit (ADU) can be a source of income if desired! It’s important to note though that an ADU cannot become a commercial space like office spaces since the primary residence must remain in place so long as any occupant(s) occupy them.

    In many major cities, accessory dwelling units are a popular solution to the housing crisis and expensive rents. Many people don’t realize that ADUs can be added as an accessory unit or created by converting parts of your existing home into new living spaces such as basements, attics, garages, side yards, and even tree houses! 

    There is no limit on how much additional floor area you can add if it meets building codes for Accessory Dwelling Units (ADU). You do not need land to build an ADU; they can be built in backyards and other small spaces too!

    We hope this article has given you a better understanding of what an ADU is, and the different types that are available. If you have any questions about whether building an accessory dwelling unit would be right for your property or how to get started on your project please contact us today! Our team can help walk you through all aspects of the process so don’t hesitate to reach out.

    Are You Looking for a Company to Build a Foundation for Your New Home?

    Spaulding Concrete has been the SF Bay Area’s top foundation builders for over 30 years.  We’re here to fix your home’s foundation, no matter what problem may exist. We have the specialized equipment, services and professional experience that you need to make permanent improvements to your building’s foundation. To get you started on the right foot, we would be happy to give you a free quote for the repair of the foundation. When you reach out by phone or email we will have one of our foundation experts answer any questions you have and explain how we can restore integrity and structural stability to your home or company building permanently. Successful concrete projects require careful planning and thorough preparation. Spaulding Concrete reviews the site and designs to ensure that the concrete and base structure follows the criteria for the planned use and that the layout and finishes are suitable for the project. The qualified concrete experts at Spaulding Concrete will be on schedule, on budget and meet or exceed standards by careful planning, professional execution, and strict quality control.

    To schedule your free quote, contact us today! We are proud to serve Orinda, Lafayette, Moraga, Pleasant Hill, Concord, Martinez, Pittsburg, Antioch, Brentwood and the surrounding areas.