How Much Does It Cost to Build an ADU?

As the need for affordable housing rises, so do alternative housing options. These include tiny homes, mobile homes, and Accessory Dwelling Units, also known as ADUs. ADUs are a great, affordable housing option. They are very versatile. For example, they can be attached or detached from your house, rented, or, in some cases, sold as an entirely separate unit.  Since ADUs are construction projects, some costs are involved. In this article, we discuss a couple of the most common ones.

How Much Does It Cost to Build an ADU Per Square Foot?

On average, you can expect that an ADU will cost about $150-$300 per square foot to build. However, finding the cost of an ADU is not as cut and dry as it sounds. As with most building projects, many variables have to be considered. If you want to get a better understanding of the cost of building an ADU, keep reading.

Size and Material

When building any project, size will be a big factor in the cost. The size of the ADU will influence how much material you will need to build it. There are a lot of materials to choose from when building an ADU. The most common ones are wood, concrete, steel, brick, and fiber. If you take the most common building material, wood, it is going to cost you around $150-$300 per square foot. 

Location

The location of your ADU can also be a big cost factor. There are two separate factors to this: location on property and location in state/country. 

Property location

Typically, renovating or adding on to a part of your house will be cheaper than building a detached ADU. The average cost to build an attached ADU is $100,000-$250,000. A detached ADU is going to cost about $120,000-$285,000.

State/country

This is one of the biggest cost factors. In some places, the price to build is just very high. For example, in Los Angeles and San Francisco, the average cost to build an ADU is $250,000 and $330,000, respectively, but California offers a $40,000 incentive for ADU builders. This helps bring the cost down. Other states don’t offer this much money, but do offer a significant incentive of some sort. To learn more, check out our Top 7 ADU-friendly states. 

Construction Type

There are two types of ADUs: detached and attached. Detached ADUs are the ones built away from the main house. Attached ADUs are built onto or are a renovated part of the main house. Most of the time, an attached ADU is the cheaper option because they are part of the existing structure. Therefore, they require fewer materials and labor. One example of an attached ADU would be a renovated attic. On average, it costs $60,000-$150,000 to finish. On the other hand, a detached ADU built from the ground up is going to cost, on average, $120,000-$285,000 to complete.

Design Complexity

While having a complex design in your ADU would look nice, it would also raise the cost. If you are set on having a more complex design, make sure to do your research on architecture firms and the fees associated with them. On average, architectural fees are $5,000-$15,000.

Permits

As with every building project, you must have the proper permits to build. The costs of permits vary depending on where you live and what you are building. ADUs need special permits, one of them being a building permit. The average cost for a building permit is $1,600. As with many other things, make sure to do more research on the cost of permits where you live.

Site Preparations

When you build anything, you have to get the site ready first. This is called site preparation. It usually includes things like leveling, grading, removing debris, and laying the foundation. An ADU costs around $1,500-$10,500. 

As you can see, it is impossible to put an exact price on building an ADU. Many variables go into building anything. The ones above are just a few of the most common ones. There are many more that I didn’t mention here. Before you go and start building, make sure to do your research about other variables.  On average, though, an attached ADU costs around $100,000-$250,000. A detached ADU costs on average between $100,000 and $300,000, though they most likely will be more because of extra utilities and labor.  

Are ADUs Good Investments?

Compared to the cost of homes, ADUs are more cost-effective. With their low prices and relatively easy-to-build characteristics, ADUs are becoming popular with the younger generations. Some other ways they can be good investments are that they can raise property value, provide extra income, and provide some extra living space. If you want to find out 5 reasons why ADUs are becoming popular, check out our blog post.

Is it Cheaper to build an ADU or an Addition?

When talking about ADUs and additions, you might think that they are just the same thing. They are not. An addition can be an ADU, though. As I mentioned earlier, an ADU has to have a separate entrance from your house. Generally, an addition is something you would use as an extension of your house instead of using it to have space for other people to live. Most of the time, an addition is considered cheaper than building a detached ADU because it uses the existing parts of your house to start from. An addition, on average, costs $80-$200 per square foot.  As I mentioned before, an addition can be an ADU, so depending on which way you look at it, it is cheaper to build an addition or an ADU.

Pros and Cons of ADUs

As with other projects, there are many pros and cons to building an ADU. Below are some of them.

Pros

Additional Income, Affordable Housing for Loved Ones, Flexible use, and increased property value.

Cons

Maintenance, property tax increase, close neighbors, and resale difficulty.

These are just an overview of the pros and cons of having an ADU. If you want to know more about the pros and cons, check out our article about What Are ADUs .

How Do I Save Money When Building an ADU?

As I mentioned earlier, many variables go into building an ADU. This means there are also many ways to save money when building. 

Simplicity

One effective way is to prioritize a simple design. A more complicated design can significantly increase costs, so if you go for a simple one, it can bring costs down.

Modular

Most ADUs are built as modular instead of stick-built (from scratch). At Zook Cabins, we offer many modular ADU options. Modular means that they are built in sections in a factory, transported to the location, and then assembled. If you would like to look at our ADU options, check out our list of ADUs.

On the other hand there are such things as prefab adus. To help you understand the difference, check out our blog on the prefab vs modular ADUs.

Follow Local Regulations

Some places have incentives and grants for ADU construction. In California, the California Housing Finance Agency offers grants of up to $40,000 to help with pre-development costs. Other states are very ADU-friendly.

Future Planning

Planning for events down the line can help with not having to do renovations or upgrades later. One way to plan is by using quality materials. This helps if you plan to keep your ADU for an extended period. You might have to spend more money at the beginning, but down the line, it could save you time and money by not replacing it.

What are some ADU-friendly States?

Many states don’t allow ADUs, but there are plenty that do or are friendly to them. Some ADU-friendly states include Oregon, California, Washington, Connecticut, and Maine. 

Oregon

Oregon is one of the leading states in ADU availability. Portland was the first part of the state to allow ADUs because of a need for affordable housing. The city even offers waivers for certain fees as an incentive for people to build ADUs.

California

California has a population of 40 million people, so there is a need for affordable housing. There have been major changes in the laws that allow ADUs. As I mentioned before, they offer a $40,000 incentive for ADU builders. They also removed the minimum lot requirement for ADUs. This makes it easier for homeowners to have flexibility when choosing how to build their ADUs.

Washington

Washington is another ADU-friendly state. They have a new law that says you can have two ADUs on your property. This is great for people who are looking for ways to rent out extra land and make a little extra income. Before you start renting out your ADUs, make sure you research your town’s specific building codes. Some towns do not let ADUs be rented out short-term, like an Airbnb, and can only be rented out for a long-term tenant.

Connecticut

In Connecticut, they have a bill that says any place a single-family residence is allowed, ADUs are allowed as well. This makes it easy for people who want to rent parts of their property. As with Washington, in Connecticut, make sure to research your town’s specific building codes.

Maine

In Maine, some laws allow ADUs but only under certain conditions. One of these is that the ADU has to be for single-family use, but they do allow multiple ADUs on the same plot of land. Because of this, the need for large ADUs is nonexistent.

To learn more about these states, plus two more, check out our blog post on the Top 7 ADU-Friendly States. 

Conclusion

With the cost of homes rising, ADUs are quickly becoming many people’s source of lodging. They are a great choice for extra income or just extra living space. When you are looking to build an ADU, many costs go into it. This is why it is impossible to put a single cost on an ADU. Some factors that come into play when building an ADU are size, material, location, and type. Remember to do your research on the factors in this article and see how much they will affect you should you choose to build.

If you decide you would like an ADU, feel free to contact us here at Zook Cabin to get started.