in-law unit

5 Mistakes to Avoid When Adding an in-Law Unit to Your Property

Whether renting or paying a mortgage, today’s housing market isn’t for the weak-hearted. And if you’re an older person—or have elderly parents—navigating the market can feel overwhelming.

The challenges of the current market are one reason many homeowners choose to build an in-law unit on their property. Keeping parents close while giving them independence is also a driving force behind the decision.

It’s not only those families with elderly loved ones that benefit from adding an ADU house. With an unprecedented number of boomerang kids moving back in with parents, an ADU makes things easier for both parents and kids.

While it’s an excellent idea, building an ADU comes with some unique considerations that catch many people off-guard. In this article, we’ll explore how you can avoid five common mistakes made when adding an ADU to your property.

1. Not Making Sure Your Property Is Eligible

Each state has rules and regulations for building ADUs. Every city also has ordinances governing these structures.

Before you start designing a backyard home, you must check with your local zoning or building department. You need to know whether your lot is eligible for building an ADU.

Here are a few things your city will consider before allowing you to build:

  • Density
  • Maximum Height
  • Easements
  • Setbacks

Density refers to the number of dwelling units the city allows on a lot. Many towns limit the height of new buildings. You won’t get a building permit if your ADU’s height exceeds the limit.

Other factors may limit eligibility to build your ADU.

For example, in San Francisco, you cannot add an ADU to a building that has had owner move-in evictions (within five years) or no-fault evictions within ten years of applying for a building permit. In 2020, the city of San Jose voted to allow small homes on wheels—a type of ADU—to be built on residential properties.

A standard tool used by homeowners planning an in-law suite is the ADU feasibility study. It’s not something you perform on your own. It’s research done by a design or planning professional.

Without a feasibility study, you won’t know for sure whether your property is eligible to build your ADU.

Next, we’ll go a little further into a discussion about easements and setbacks.

What Are Easements and Setbacks?

Even though you own the property where you want to build an in-law unit, you’ll need to be aware of any restrictions regarding your unit’s location, size, height, and shape. Cities use easements and setbacks to minimize problems caused by new construction.


Setbacks to determine how far from the property line you can build a structure. They help to protect the properties in your neighborhood.

For example, setbacks prevent oversize buildings from exceeding a reasonable height. Setbacks also prevent problems caused when someone builds a structure that encroaches on a property line.

Something to remember about setbacks is that they’re not always set in stone. 

You may apply for a setback variance if you have a unique situation. The responsibility of approving variances usually falls on the local zoning board. They may authorize if your request for a variance doesn’t negatively impact the neighborhood.


Your property likely has easements unless you have acreage in a rural area. Easements give someone other than you the right to use your land for a specific purpose.

The most common easements in urban areas are those intended for public utilities. Your ADU cannot limit a utility worker’s access to electric, water, and natural gas lines.

Your neighbor may have an easement of necessity that allows them to cross your property to access their property. Sometimes, a person buys a home with an existing private easement. Whether you’re dealing with setbacks or easements, you’ll need to include them in your building plan.

Keep in mind that even in rural areas, there may be easements, so you’ll want to make sure you’re aware of any that exist on your property before you build.

Next, we’ll discuss another mistake you want to avoid when building an in-law unit. It’s more common than you might think.

2. Building Without a Budget

Planning any home addition without first setting a budget is unwise, yet some homeowners move ahead before they fully understand the project’s costs. This is a big mistake.

The budget drives the project and should always be at the top of the to-do list. When you set the budget, ensure you’ve covered every cost associated with your ADU house project.

The budget should include expenses for the following: 

  • Design
  • Planning
  • Engineering
  • Permit Fees
  • Site Work
  • Cost of Materials
  • Labor Costs

It would help if you focused on the budget first to prevent starting a construction project you cannot afford. Your budget will help you determine what type of ADU house will best suit your needs without overspending. With a well-thought-out budget, you’re less likely to deal with project scope, which can derail your build.

A Few Words on Money Matters

Caring for elderly parents or welcoming adult kids back into the fold aren’t the only factors driving the ADU boom.

When you build an in-law unit, you can enjoy a healthy return on your investment. If you sell your home in the future, your backyard house could increase the value of your primary residence. Many homeowners also view an in-law unit as a way to generate retirement income.

When you set your budget, you want to plan with the future in mind.

It’s about maximizing your budget to get the most house for your money. The savvy homeowner realizes there may be some hidden costs that aren’t immediately apparent when you’re in the early stages of putting a budget together.

Those costs include:

  • Utility Upgrades
  • Site Work
  • Interior Finishes

The electrical panel in your existing house may not support an in-law unit. If you have a 100-amp panel, you’ll likely need to upgrade to a 200-amp panel. It would be best if you planned to spend up to a couple thousand dollars for the upgrade, just to be safe.

The next hidden expense, site work, includes things you must do to prepare your property for the construction of the ADU house. Site work may consist of tree removal or leveling a sloped area in your backyard It can also include trenching and removal of hardscape, etc..

Planning for the interior finishes presents a challenge due to variations in price associated with your chosen designs. There’s usually a significant difference between top-of-the-line and off-the-rack options when shopping for appliances and flooring.

Consider how you’ll use your ADU house when budgeting for interior design costs. Perhaps, you’ll decide to live in it one day when your adult children get back on their feet. If you can earmark part of the budget for it, why not splurge a little?

After you estimate hidden costs, you can wrap up setting the budget and move on to planning, which, consequently, is another area where you have the potential to make mistakes.

3. Mistakes Associated with Poor Planning

Poor planning can leave you stuck with an in-law suite that doesn’t meet your present or future needs. Working with a professional ADU design team can easily avoid mistakes associated with poor planning.

A design team will ask many questions during the planning process. Your answers help them propose a design that considers the lifestyle and habits of the people who will live in the ADU house. 

Maybe your parents are still independent but plan to age in place in the in-law suite. Their needs will likely change, so you’ll want to prepare for a day when they may deal with mobility issues. You may decide to install safety features you wouldn’t consider if a younger person were to live there instead.

Your design team will help you look ahead and plan accordingly. That way, you minimize the risk of investing in a unit that won’t work well for you in the long term.

4. Not Planning Efficient Use of Limited Space

Most in-law suites don’t have a lot of square footage. Most people underestimate how much space they will have in the finished unit. They end up with a small living space that feels even smaller than it is because they don’t utilize the limited space well enough.

You have options to make a small home feel more spacious. Increasing ceiling height is one solution. You can also orient the building to maximize airflow and natural lighting. Adding skylights can boost natural light.

The limited space in an ADU can create issues with inefficient sound separation. In small living spaces, you need a sound barrier between rooms that get the most noise (kitchen and bathroom). Consider installing acoustically insulated walls.

Installing pocket doors not only saves space, but these doors also make your living area feel more open. Consider opaque or transparent glass pocket doors as they let more light in, which can make a room feel larger.

If you plan with optimizing space in mind, you’ll never feel boxed in or cramped.

What about storage?

It’s no secret that storage can be a significant problem when you have a small living area. Here are two ideas to help increase usable space: 

  • Built-Ins
  • Storables, a.k.a., Stowables

Even the smallest homes need storage space. Built-in wall storage helps reduce clutter. You can even design a built-in for a large-screen TV, which eliminates the need for an entertainment center or bulky TV stand.

Storing furniture when it’s not in use is another way to optimize space. You can find all sorts of stowable furniture, including best, sofas, and dining tables. You’re probably familiar with the Murphy bed, but you’ll also want to check out collapsible bunk beds, roll-aways, and platform beds (for under-bed storage).

The last mistake we’ll cover in this article is one that can ruin the entire experience of building an in-law suite—it’s working with the wrong team.

5. Putting Together the Wrong Team

When you invest in an ADU house, you need a team that is knowledgeable, honest, reliable, and a pleasure to work with—easier said than done for most people. The challenge is finding your tribe without sacrificing your budget or ideas.

Unfortunately, the primary reason people end up with a team they can’t work with is that they hire contractors based on cost. Low bids sound enticing when you’re trying to stick to a budget, but cheaper doesn’t usually mean better. In fact, never does.

By getting multiple estimates, you can avoid many problems associated with hiring the wrong people. But more importantly than the estimate, or even the estimate’s thoroughness, is the quality of the team. Do you trust their experience? What does their portfolio look like? And the big one, how long have they been successfully building ADUs? Questions like these can help answer if the contractor is the right one for you.Checking references is another proactive last step you can take. Hiring the right design team means making sure they bring a few critical skills, including:

  • Specializes in ADU Design
  • Understands Cost-Benefit Tradeoffs
  • Familiar with Current ADU Regulations
  • Able to Analyze a Property’s Features and Constraints
  • Years of successful experience (leads to true pricing and costs)

The ability to look at a property and understand the features that will make it possible to build an ADU house and any constraints is critical. Finally, you want a design team that listens to your goals and can help you meet them. 

Ready to Design Your In-Law Unit?

It doesn’t matter what type of building project you choose to work on; there’s always the potential to make mistakes. As you can see, it’s not difficult to avoid many of the errors associated with building an in-law unit.

Feasibility studies, setting a budget, planning so that you optimize space, and working with a design team to make sure you build an ADU home that meets current future needs are all steps you can take to side-step mistakes.Working with the right team nearly guarantees a successful building project. The professionals at Acton ADU work with homeowners just like you to bring their ideas and dreams of an ADU house to life. Reach out today, and let’s get your project started!

Similar Posts