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How To Add an In-Law Suite to Your Home (2024)

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Thinking of converting your basement, attic, or garage into an in-law suite? We’ll walk you through everything you need to know.

Written by Shane Sentelle Updated 11/01/2024

Multigenerational living arrangements are a growing trend. According to the National Association of Realtors, 14% of all home buyers in 2023 were motivated to purchase a home that could accommodate multiple generations of their family. This trend shows no sign of slowing down, as many baby boomers consider moving in with their children to avoid the high cost of assisted living facilities and retirement communities.

In this article, we’ll explore the process of adding an in-law suite to your home—including the factors to consider before starting the project.

Why Add an In-Law Suite to Your Home?

One common reason to add an in-law suite to your home is to provide a comfortable and convenient living space for aging parents or other family members. As the baby boomer generation reaches retirement age, many families choose to live together in multigenerational settings. An in-law suite can provide the extra space needed to accommodate everyone comfortably.

In addition to the personal and familial benefits of having an in-law suite, there are financial and real estate considerations. Adding an in-law suite can increase your home’s value, making it a smart investment. Plus, according to a report by the National Association of Home Builders (NAHB), almost one in five young adults live in parental homes.

Further, an in-law suite can be a cost-effective alternative to paying for senior care or moving long-distance to be closer to aging parents. The suite can also serve as an income source if you rent it out when it is not occupied by a family member.

What Should an In-Law Suite Contain?

An in-law suite is a distinct space that provides comfort and privacy for aging parents, extended family members, or guests. The goal is to make it look, feel, and function as much like a separate apartment as possible. To achieve this, an in-law suite should contain the following key elements:

Kitchen area with sink: The kitchen area should be fully functional with a sink, refrigerator, and basic cooking facilities, such as a stovetop and microwave. This enables occupants to prepare their own meals, increasing their independence.
Full, private bathroom: The bathroom should include a shower or bathtub, a toilet, and a sink. This gives the occupants space to get ready in the morning and take care of their personal hygiene needs. Like a functional kitchen, a full bathroom enables autonomy. It also provides a sense of privacy, which is especially important for aging parents who may need assistance with personal tasks.
Bedroom with door: The in-law suite’s bedroom should be a separate room with a locking door. It should be large enough to comfortably fit a bed, a dresser, and any other necessary furniture. With a private bedroom, the occupants have space to rest and recharge. The locking door will provide a sense of security and more control over who enters their space.
Living room or lounge area: Be sure to include a distinct living area outside the bedroom. Since the occupants will use this space to relax, watch TV, or entertain guests, you should furnish it with a sofa, chairs, and an entertainment center, including a television.
Separate entry and exit: Provide a separate entrance to ensure that the occupants of your in-law suite can come and go as they please without disturbing the rest of the household.

Including these key elements will ensure your in-law suite is comfortable and convenient for renters or loved ones. If you already know who will occupy the space, consider customizing the suite to better accommodate their needs, routines, and hobbies. For instance, you might add a computer desk, a record or CD player, a landline phone, or a table for board games.

Where Is the Best Location for an In-Law Suite?

Each in-law suite location has advantages and disadvantages, so consider your family’s specific needs and circumstances. Regardless of your chosen location, prioritize the occupants’ privacy, comfort, and independence.

Basement

Converting an unfinished basement into an in-law suite can be cost-effective,* as it typically requires less renovation and construction than other options. However, you’ll need to account for the following:

Height of the ceiling: Ideally, the basement ceiling should be at least 7 feet high to accommodate an in-law suite. This is high enough to feel spacious and to provide adequate headroom for occupants to move around comfortably. If the ceiling is lower than 7 feet, you may need to excavate the basement to increase its height. This will add to the cost and complexity of the project.
Presence of windows: Windows provide natural light, which can help the space feel more open and airy. They can also be used as emergency exits in case of a fire. If the basement does not have windows, install several to enhance safety and keep the space from feeling claustrophobic. Consider using top quality window brands for your project.
Potential for mold: Basements are often damp, which can lead to the growth of mold and other harmful substances. To prevent mold, it’s important to waterproof and properly ventilate the basement. Allowing air to circulate will prevent moisture buildup. You may also need to install a dehumidifier, French drains, or a sump pump.

* According to HomeAdvisor, a basement conversion can cost anywhere from $12,000–$34,000.

Attic

Converting an attic into an in-law suite is not as common as converting a basement, but it can be a viable option if your house has a large attic. Here are some important considerations when converting an attic into an in-law suite:

Ceiling height: The ceiling in your in-law suite should be at least 7 feet high for ease of movement and spaciousness. If your attic ceiling is lower than that, you may need to raise the roof or install a dormer to increase its height.
Natural light: As you divide the attic into distinct areas, ensure each room has a window or skylight, if possible. Windows will provide natural light and ventilation throughout the space.
Accessibility: To ensure your in-law suite has its own entrance, you must install an exterior door and a sturdy staircase leading up to it. You might also consider having a sturdy and accessible interior entrance leading into the rest of the house.
Ventilation: Like basements, attics are prone to mold, mildew, and issues resulting from moisture and a lack of air circulation. You may need to install a dehumidifier or attic fan to help with ventilation.
Insulation: Because hot air rises, attics can become overly warm in the summer. Without proper insulation, they can also become very cold in the winter. High-quality insulation will help keep out unconditioned air and ensure a comfortable temperature year-round.

According to SoFi, finishing a walk-up attic can cost $8,100–$26,000.

Garage

Converting a garage into an in-law suite can be practical if you do not need that space for vehicle parking. You can do this with either an attached or detached garage. A detached garage allows you to build an apartment above the garage, which lets you retain your covered parking spaces. Here are a few things to consider when converting a garage into an in-law suite:

Structure: Before converting your garage into a living space, make sure it’s structurally sound. Inspect the foundation, walls, and roof to see if anything needs to be reinforced, repaired, or rebuilt.
Insulation: While attics tend to get hot and humid, garages often feel cold and drafty. High-quality insulation can help prevent heat loss in the winter and heat gain in the summer.
Utilities: Chances are, your garage does not have its own plumbing. In that case, you must install a plumbing system to accommodate the kitchen and bathroom. You should also ensure the garage has a separate electrical panel and sufficient outlets.
Access: Most garages already have a separate entrance. However, if you build an in-law suite above your detached garage, you must add a new door and a staircase to the second level.

According to HouseLogic, converting a two-car garage into a living space with a bathroom can cost $35,000–$75,000.

Other Rooms

If you do not have a basement, attic, or garage, you may be able to convert other rooms into an in-law suite. This works especially well if your kids have already moved out. In that case, you can easily move your parents into those rooms. First-floor rooms are ideal, as they will be more accessible for occupants with mobility issues.

One option is to reconfigure extra bedrooms to build an in-law suite. If you only have one bedroom with an attached bathroom, you may need to add a bathroom or convert an existing one into an en-suite bathroom. You might also be able to knock down a wall to create a large suite or cut a new doorway to join two rooms into one suite.

Another option is to remodel a different finished space, such as a family room or rec room. If you already have a finished attic or basement, for instance, adding an in-law suite will be that much easier.

How To Make Your In-Law Suite Accessible

Aging and elderly individuals often encounter mobility issues and need assistance with their daily routines. At that point, accessibility is crucial. Here are a few things to consider as you design your in-law suite:

Doorways: Doorways should be at least 32 inches wide to accommodate wheelchairs or walkers. However, 36 inches is better.
Flooring: Flooring should be slip-resistant and easy to navigate with a walker or wheelchair. Carpet is not recommended.
Bathroom: The bathroom should include grab bars near the toilet and shower, a handheld shower head, a roll-in shower or tub with a seat, and a sink with knee space underneath. Learn more about the cost of a full bathroom remodel in our in-depth article
Lighting: The in-law suite should be brightly and evenly lit. Dimmer switches and task lighting, such as under-cabinet lights and reading lamps, can also be helpful.
Future accessibility: Plan ahead for the possibility that you may need to install other accessibility features, such as a ramp or chair lift.

Be sure to give some thought to moving logistics. Adding an in-law suite can be a big change, and you can expect a few hiccups during the move. However, hiring professional movers will free you up to focus on your family during the transition, which will help the process go much more smoothly. Many of the top-rated moving companies offer generous discounts for senior citizens.

Our Conclusion

The rising cost of assisted living facilities and the growing trend of multigenerational living make adding an in-law suite a wise choice for many families. Still, the decision to add an in-law suite to your home is a personal one that should be based on the specific needs and circumstances of your family. Though it may seem daunting, carefully considering the cost, space requirements, and customization needs can make the process easier.

FAQ About In-Law Suites

Is a mother-in-law suite a good investment?

Yes, a mother-in-law suite is a good investment. Although building one can easily cost $40,000–$130,000 according to HomeAdvisor, that number pales in comparison to the average cost of assisted living facilities and nursing homes. According to Genworth, the median cost of an assisted living facility was $5,350 per month in 2023. The addition may also increase your home’s value, and you can rent out the space when unoccupied for extra income.

What is the difference between an in-law suite and an ADU?

The main difference between an in-law suite and an accessory dwelling unit (ADU) lies in each one’s purpose and location. An in-law suite is typically located within the main residence and is designed to provide living space for extended family members, while an ADU can be a separate structure and can be used for various purposes.

What is another name for an in-law suite?

People may refer to their in-law suite as a guest house, casita, granny flat, second unit, mother-in-law suite, family suite, second unit, accessory dwelling unit (ADU), or home addition.

How much does it cost to add an in-law suite to your home?

According to HomeAdvisor, adding an in-law suite to your home can cost $40,000–$130,000. The final price will depend on the specifics of your project, including where the suite is located and how much work must be done.

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