A mother-in-law suite is a private residence that shares a property lot with a single-family home. It can be a standalone home for family members or guests, offer opportunities to collect rent, or fulfill a specific function (like a home office).
- Mother-in-law suites can be attached, inside the primary residence, or separate.
- These suites offer housing for family members or renters.
- Having a mother-in-law suite can improve your property’s value — but also increase your property taxes.
A mother-in-law suite needs to accommodate residents independently from the primary residence, so it must have each of the following:
- Private entrance (at least one, depending on local zoning laws)
As long as it meets these criteria, a suite can take any number of forms. It can be attached or detached to the main house — a basement apartment or a guest house in the backyard, for instance.
🤔 Whether it’s attached to the main home or separate, a mother-in-law suite and the primary residence cannot be sold separately, as they’re technically parts of the same lot and property!
A mother-in-law suite can help homeowners meet various needs.
Mother-in-law suites go by countless other names in the U.S., depending on context or the region. Here are just a few:
- Accessory dwelling unit (ADU)
- Carriage house
- Coach house
- Granny flat
- In-law suite or apartment
- Mother-daughter house
- Multigenerational suite
- Secondary suite
Uses for mother-in-law suites
Homeowners often use mother-in-law suites as temporary or permanent housing for family members or as rentals.
U.S. households are increasingly becoming multigenerational, meaning three or more generations of one family live in the same household.
From 2011 to 2021, the number of multigenerational households in the U.S. nearly quadrupled, with over one in four adults living in a multigenerational household.
Long-term housing (for loved ones who are aging or have a disability)
A mother-in-law suite can be an affordable alternative to other long-term care options.
The median monthly cost for a private room at a nursing care facility, for instance, is over $9,000.A mother-in-law suite could shrink that cost significantly while keeping your family closer to you.
That’s how many adults in the U.S. who care for family, as of 2020. In other words, one in five U.S. adults are unpaid caregivers. The median monthly cost for a private room at a nursing care facility, for instance, is over $9,000.
Real estate rentals
Renting out your mother-in-law suite is a great way to dip your toe into real estate investment — and can be much easier and less expensive than, say, buying a new property outright.
Additionally, mother-in-law suites usually raise a property’s value. Forbes found home sale prices for those with mother-in-law suites have been increasing at a greater rate than overall home prices.
Other uses for mother-in-law suites
- Guest house
- Home office or work space
- Short-term rental through services like Airbnb or Vrbo
Should I build a mother-in-law suite?
|Right for you if you want to...||Wrong for you if you don't want to...|
|✅ Arrange housing for loved ones||❌ Pay for new construction|
|✅ Collect rental income||❌ Deal with complicated zoning regulations|
|✅ Increase your home's value||❌ Pay higher property taxes|
Building a mother-in-law suite
Large and detached mother-in-law suites can cost $60,000–300,000, while additions or conversions can cost $15,000–175,000.
Prefabricated homes are typically built and assembled off-site in a factory, then installed onto a property. This method can be cheaper (and greener!) than conventional home construction.
Adding a mother-in-law suite involves more than the construction itself. The process often involves:
- Paperwork and applications for site and zoning permits
- Site preparation before construction
- Connecting utilities during and after construction
🤔 Other considerations for building a mother-in-law suite
State or local zoning laws may require the mother-in-law suite to be occupied by a family member, meaning you can’t rent it out. Other regulations may make getting a permit difficult — or ban this type of housing altogether.
If you’re part of an HOA, you might need to pay fees to build an addition. Some HOAs even have their own restrictions on the size or type of new construction.
Types of mother-in-law suites
🏘 Detached mother-in-law suites
Detached mother-in-law suites are standalone from the main home. Think: a tiny home in a backyard.
Both structures still share the same plot of land, though they might have separate utilities, depending on the suite’s setup.
Examples of detached mother-in-law suites
- A guest house (sometimes called a coach house)
- A prefab tiny home
- A detached garage converted into a living space
🛋 Attached or interior mother-in-law suites
Attached mother-in-law suites are additions to existing homes — either extensions or spaces within the house itself.
While interior suites (like a basement apartment) are inside the main home, they must still have their own bedroom, bathroom, kitchen, and private entrances.
|Examples of attached mother-in-law suites||Examples of interior mother-in-law suites|
|Living space above attached garage||Basement apartment|
|Converted attached garage||Converted attic apartment|
|An addition to existing home|
Are mother-in-law suites common?
While mother-in-law suites aren’t overly common, they are significantly growing in popularity — as of 2020, there were at least 1.4 million mother-in-law suites in the U.S.
Over the past few years, cities and states experiencing great population increases have seen a boom in mother-in-law suite construction,multigenerational housing.coinciding with the growing popularity of
The construction boom is also the direct result of states and cities pursuing ways to build more housing. In 2017, several California laws streamlined mother-in-law construction permits, resulting in a massive surge in permits and suites.
Frequently asked questions about mother-in-law suites
Mother-in-law suites are commonly used as homes for in-laws or other family members, temporarily or permanently.
If you’re willing to spend the time and money for new construction, a mother-in-law suite can be a good investment. You can use the space to house guests or family members, rent it out to tenants, or as a work space. Just know you’ll pay more in property taxes.
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