Most people are surprised when they hear the REAL cost to build an ADU (accessory dwelling unit). We come across articles all the time misstating the actual cost of building these mighty units from the ground up, some claiming you can build an ADU for as low as $20,000 (we wish!)
But, after helping over 300 homeowners build their ADUs, we want to help clear up those inconsistencies.
Cost Per Square Foot is Deceiving
Clients always want to know the average cost per square foot numbers for an ADU, but the truth is it’s not the best way to gauge the final cost of your project.
For starters, ADUs cost more per square foot than typical single-family homes for several reasons.
- There are fixed costs associated with permitting and design fees.
- Margins are smaller for general contractors, subs, and architects.
- ADUs require new foundations, new walls, plumbing, electric, heating and cooling, and a separate roof, just like a regular house.
- There are no economies of scale. You know how you get a significant discount if you buy groceries from Costco because you’re buying in bulk? Building a tiny house is the opposite.
- ADUs still require a bathroom and kitchen, which are ‘expensive’ square footage.
- Because the units are smaller the cost per square foot isn’t offset by extra bedrooms, large living rooms, and hallways you find in larger homes. This space is considered ‘cheaper’ square footage and brings the average cost per square foot down.
The cost per square foot of an ADU can differ dramatically depending on the size and structural form
- The larger the unit, the cheaper your cost per square foot will be. Detached units can be up to 1,200 square feet or larger if you’re converting an existing space. A 1,200-square-foot unit will probably be cheaper per square foot to build than a 450-square-foot unit.
- Building up is more expensive. Most people instinctively want to build an accessory dwelling unit above their garage. If your budget is tight, stick to single-story. Building up will add ~$50/square foot to your project.
- In most cases, a garage conversion is the most affordable way to convert space into an ADU. If your budget is modest keep the existing envelope of the garage, meaning don’t expand on the current footprint. This will add extra cost.
Region Will Impact Your Final Cost
If you live in San Diego, your final cost is going to greatly differ from the final cost for a project in the Bay Area. We’ve broken down everything you need to know below.
Cost Per Square Foot to Build an ADU in San Diego
The cost to build an ADU in San Diego starts at about $350 per square foot.
Wow. The cost to build an ADU in San Diego seems expensive.
The price tag on an accessory dwelling unit can scare people, but here’s a smart way to assess your investment.
- Look up the median value per square foot in your neighborhood. For example, in North Park, the median home sells for $834 per square foot.
- Let’s say you build a 550-square-foot unit in North Park for $400 a square foot.
- You may spend $220,000 on your project, but you’re gaining close to $458,700 in value.
- That means you’re adding more than 239K in equity to your property. Plus, that doesn’t take into account the added value passive rental income brings.
- In North Park, a 1-bedroom apartment can rent for up to $2,500 a month.
- (Check out the video above. This is a real example!)
Suddenly, the $220,000 price tag seems a lot more manageable, even savvy.
Cost Per Square Foot to Build an ADU in Los Angeles
The cost to build an ADU in Los Angeles starts at about $350 per square foot.
Los Angeles ADU prices are fairly similar to the prices in San Diego.
The price tag on an accessory dwelling unit can scare people, but here’s a smart way to assess your investment.
- Look up the median value per square foot in your neighborhood. For example, in the Echo Park neighborhood, the median home sells for $854 per square foot.
- Let’s say you build a 550-square-foot unit in Echo Park for $390 a square foot.
- You may spend $214,500 on your project, but you’re gaining about $469,700 in value.
- That means you’re adding about $255K in equity to your property. And it doesn’t take into account the added value passive rental income brings.
- In Echo Park, a 1-bedroom apartment will rent for a minimum of $2,200 a month. Many rent for far more.
Cost Per Square Foot to Build an ADU in the Bay Area
The cost to build an ADU in Los Angeles starts at about $500 per square foot.
The price tag on an accessory dwelling unit can scare people, but here’s a smart way to assess your investment.
- Look up the median value per square foot in your neighborhood. The median home in San Jose sells for about $823 per square foot.
- Let’s say you want to build a 750-square-foot accessory dwelling unit in your neighborhood for $525 a square foot.
- You’re going to spend about $393,750, but you’re gaining $617,250 in value by adding to your home.
- That means you’re adding about $223K in equity to your property. Better yet, that still doesn’t consider the added value passive rental income brings.
- In San Jose, a 1-bedroom apartment will rent for about $2500 a month. Many rent for more.
Not so scary anymore, is it?
Many Ways to Build an ADU
Most people are familiar with the conventional “constructed on-site” way of building an ADU, more formally known as a conventional stick framing. However, what most people don’t know is that there are actually two more ways that you can add an ADU to your property: prefab and panelized modular.
Contrary to popular belief, all three construction methods will yield a similar total cost. So, when you’re deciding between traditional, prefab, or panelized modular, things like timeline, customization, and lot characteristics should be taken into consideration.
Traditional Construction
Also known as stick-built construction, traditional construction is the most well-known among the methods. It involves a linear timeline consisting of site prep, foundation pouring, framing, drywall, and finishes.
This is the ideal construction method for homeowners looking for complete customization. However, traditional construction loses points in the length of time it takes to complete a project. Since the project is on a linear schedule, each step needs to be completed before the next phase can be begin. As you can imagine, this can lead to a lengthy construction period, sometimes lasting up to two years depending on the size and complexity of the project.
But, this can be a small price to pay for homeowners that aren’t on a strict schedule and value complete customization of their ADU.
Prefab
When you’re driving down a highway, you’ve probably come across what looks like a house being hauled down the road by a big rig with a “wide load” sign strapped to its back. That’s a prefab.
A prefab ADU unit is built in a factory while another team works on prepping the lot for installation. Once completed, the ADU is hauled to your property where it can be set up in just a couple of weeks, sometimes even days. This option is great if you’re looking for a quick turnaround and don’t mind being flexible with the design and layout.
A good prefab company will have a large library of designs that you can choose from, but if you have a complex lot or are looking for something unique, this may not be the construction method for you.
Prefabs typically cost about the same as a stick-built. Click here for a complete cost breakdown of prefabs.
Panelized Modular
Panelized modular is where the framing package for your ADU is built offsite and shipped to the job site. Unlike prefabs, however, this type of construction is completely customizable.
You’re pretty limited with prefab designs and modifications to the standard designs of the factory can be costly, but the great thing about panelized modular is that the entire structure and layout can be designed and customized to your liking.
The price for these is similar to prefabs as well.
Finally, panelized modular are appraised much higher than prefabs if you decide to sell your property.
Additionally, contractors will sometimes draft pre-made plans for ADUs at a discounted price. For example, instead of paying $15,000 on an ADU plan from scratch, you can purchase one of these for just $5,000 and make modifications to it to fit your needs.
While not as swift as prefab construction, the construction timeline of panelized modular is still impressive. A project can be fully finished in as little as three months.
Check your address to get connected to some of these contractors too!
Are ADUs a Good Investment?
Yes, adding an ADU to your property can be an excellent investment. However, keep in mind that ADUs are a long-term investment. If you really want to see a huge return, you should be prepared to keep your property for several years.
We’ve calculated that even a $150,000 garage conversion, maintained over a 30-year period can bring 1.5 to 2 million dollars in value between grossed rental income and property value increases. That’s a 15x return on investment.
How to Maximize Your ADU Investment
If you do decide to build an ADU, build as large as your lot will allow. If you can comfortably fit 800 square feet in your backyard, we recommend our clients to do so.
Why?
The fixed cost.
Relative to what you’re already spending, adding 200 square feet won’t dramatically impact your budget, but it could significantly increase what you can charge for your rental. It could also be the difference between renting to a couple vs. a single-person unit or having a one-bedroom vs. two-bedroom ADU.
The cost of your ADU will also greatly depend on the level of finish you want. If you want standard appliances and finishes, the finishing cost of your unit is going to be dramatically lower than if you’re ordering high-end luxury custom items.
The choice is really yours as to how you want your finished product to look and also plays a large part in how much you’re going to rent out your unit for.
Another way to maximize your ADU’s investment is to create garden spaces. Gardens and outdoor area is a luxury most renters don’t have access to. With California’s fabulous weather, a patio with an outdoor table can feel like a 2nd living room and be used all year long.
This is a very inexpensive space to create but can make your property much more desirable.
For more tips and tricks on ADUs download our free tools.
But with all this added value, many homeowners worry about how this will affect their property taxes.
Does adding an ADU increase property tax?
Adding an ADU does increase your property tax, but the nice thing is that it will not trigger a reassessment of your entire property.
For example, say you bought your home in 1986 and decide to add an ADU to your property, the state will only assess your most recent addition. You’ll pay property taxes for your ADU for the present year while you continue paying the 1986 property taxes for your main home.
This is called a blended assessment.
Does adding an ADU add value to your home?
Absolutely!
Not only does an ADU add monetary value to your home, but it also adds lifestyle benefits.
Whether you build one to house an aging family member, rent it out to an individual, or use it as a guest house for visiting friends and family, an ADU has a multitude of uses that will make your life easier.
When the time comes for you to sell your home, the ADU will definitely add resale value in comparison to a home without an ADU.
With all this talk about money, you may be wondering how people can afford to make these investments to begin with.
Can you get a home loan for an ADU?
Yes, in fact, most people will take out a loan to build their ADU.
The most common way is through a home equity line.
A home equity line of credit allows a homeowner to borrow money from a lender where the collateral is the borrower’s equity in his or her house before any improvements are added. Typically, homeowners must have at least 10% equity in their home or 20% if an investment property or second home.
Another option is through a construction loan.
A construction loan evaluates what the future value of the property will be after the project is completed and allows a homeowner to borrow against that amount. A bank will send the plans to an appraiser to have the project and property appraised. Qualification for a construction loan is usually more difficult than getting a credit line or home equity line of credit.
The final type of loan is a Homestyle Renovation loan which will help if you have limited equity in your current property, or are purchasing another property that needs improvements that you can finance before the work is started.
The HomeStyle Renovation mortgage provides a convenient and flexible way for borrowers considering home improvements to make repairs and renovations with a first mortgage, rather than a second mortgage, home equity line of credit, or other more costlier methods of financing.
If you’re wondering how much your ADU will cost, you can download the free cost estimator here.
What are some unexpected costs when building an ADU?
Unexpected costs are part of any construction project and ADUs are no exception. Unexpected costs might include:
- Soil testing
- Lot grading for sloping
- Foundation upgrades
- Tree or boulder removal
- Complex utility trenching
- Other permits like coastal overlay
- Complying with accessibility requirements in some areas
These costs will vary, which is why having a contingency budget of at least 10% of your expected cost is always a good idea to be prepared.
However, some costs can be more subtle and harder to anticipate, such as delays caused by unforeseen weather conditions, supply chain issues, or changes in local building codes. It’s essential to account for these possibilities by working with experienced professionals who can help identify potential challenges early on. Additionally, as the project progresses, you may encounter requests for changes in design or materials that could impact both cost and timeline. By remaining flexible and proactive, you’ll be better positioned to handle these surprises without derailing your overall budget or project timeline.
How to Start Your ADU Project
It’s easy to get overwhelmed with all of the regulations, information, permits, and vetting that you have to get through to build your ADU, but Maxable has a proven formula that has worked to help thousands of homeowners kickstart their projects.
We make ADUs easy!
Our team of experts will evaluate your property and match you with the best designers and general contractors in your area based on your needs and budget. All you have to do is check your address here!