In its simplest form, a mother-in-law suite is a residence created within a home,  an addition built onto a home, or a separate dwelling unit intended for the use of an in-law or relative. The suite can be connected to or built on the same lot as a home occupied by other family members. 

Often, the purpose of a mother-in-law suite is to make it possible for elderly family members to live near their adult children or family members yet still maintain their independence and privacy.

That is very common in multi-generational households where children often live with their parents and grandparents in the same house. 

The concept of a mother-in-law suite, or now more popularized as the “granny flat,” has been around for decades. It was most popular in post-WWII America until zoning laws were put in place that eventually shut down their construction.

Today, the mother-in-law suite, whether it’s a portion of a house that has been remodeled to accommodate a relative or a smaller, detached “granny flat,” is beginning to see a resurgence with homeowners.

 

What makes up a mother-in-law suite?

A typical mother-in-law suite consists of a sleeping quarter, living quarter, kitchen, and bathroom.

Though it can be attached to the main house, the living quarters typically remain separate from the rest of the house and household, close enough so grandparents can help with grandchildren or adult children can care for their parents.

Mother-in-law suites can be as simple as a single room with a bed, couch, and place to eat, along with access to a bathroom, but ideally, it would have its private bathroom.

They can be located in a separate portion of the house, like a basement with a different door, garage, or a remodeled attic suited to the residents’ needs.

 

Why are mother-in-law suites so popular?

Mother-in-law suites are becoming a more and more popular home trend among families today. According to USA Today, approximately 51 million Americans live in multi-generational households, a 10% increase since 2007.

One reason they are so popular is that this living arrangement allows both generations to share in the financial responsibilities of homeownership.

Mother-in-law suites can also provide an independent living situation for post-graduate adult children, which can help keep their debts low as they begin their careers and start saving for their own homes.

Another reason why in-law suites are so popular today is the need to downsize and the sharp rise in the cost of assisted living facilities for aging adults.

Nationwide, the average monthly cost of assisted living in the United States is around $4,300. This amount can place a financial burden on both parents and children.

Yet a third reason there has been increased interest in an “in-law” suite is a rise in the number of people who can permanently work from home. According to Pew Research, about 54% of employed workers would like to work from home. 

That is nearly a 30% increase over the number of workers working from home before the Coronavirus pandemic. Many of these workers prefer a designated area to conduct their business while keeping the family living area separate. 

 

What are the common types of mother-in-law suites?

Interior mother-in-law suites are located within the house where the family resides. That could be a converted basement or the central portion of the house, such as a study or den. Some homes have floor plans that comfortably accommodate bringing in extended family members.

These homes have bedrooms at opposite ends and separate bathroom facilities for both generations. However, they still share a living room, dining area, and kitchen space.  

If the basement has been transformed into an in-law suite, it will typically have its kitchen, bedroom, bath, and living area. Often they have a walk-out basement that provides a separate entrance into the house.

An attached mother-in-law suite includes a separate living space built onto an existing home and is often linked to the side of the house or the back as an addition. 

Detached mother-in-law suites are accessory dwelling units (AUD), granny flats, or secondary suites. These are typically smaller, separate homes constructed on the same lot with a single-family residential house. They vary in size, features, and styles to suit personal tastes and needs. 

An attic or garage in-law suite is a suite where the garage or attic portion of the home is remodeled to accommodate in-laws or relatives. The remodel typically includes a bedroom, bathroom, kitchen, and living area.

Sometimes can find an adequate attic space over a stand-alone garage. That provides even more privacy than an attic located in the main house.  

 

How much does a mother-in-law suite cost to build?

The cost to build a mother-in-law suite varies greatly depending on which type of mother-in-law suite best suits your situation, how big of a suite you plan to create, and the specific amenities you want to incorporate into the space. Let’s look at each option a little closer.

 

Interior mother-in-law suites  

Like each of these options, you can spend quite a bit remodeling or finishing a basement into a mother-in-law suite.

However, redoing a basement or portion of the main house into a separate suite for mom can be a less expensive option than building a detached mother-in-law residence from scratch. 

According to HGTV, it can cost less than $3,000 to more than $200,000 to convert a basement into extra usable space.

However, keep in mind that you could run into problematic issues such as water damage that would require costly remediation before getting started on the actual addition when working in a basement.

 

Attached mother-in-law suites 

Buildinganadu.com states that the cost to build a 500 square foot attached mother-in-law suite costs as little as $106,000 or $216,000 depending on the full scope of the project.

But this can vary depending upon the size of the space, how elaborate it is, and whether you decide to do any of the work yourself.

 

Detached mother-in-law suites 

According to Bob Vila, the cost to buy a new prefab detached granny pod can range from as little as $30,000 for a “bare-bones” structure, up to $125,000 on the high end.

That includes the cost of delivery and placement on an already constructed concrete pad. But, of course, the cost to build a detached structure can be much higher, should you decide to create a smart home, for example.

 

Garage mother-in-law suites 

Bob Vila expects to spend $15,000- $20,000 to convert a garage or existing shed into a mother-in-law suite.

As you can see, the cost to remodel, build, or buy space for a mother-in-law suite depends on many individual factors. Unfortunately, that makes it difficult to pinpoint an exact price in any given situation.

However, starting with space you already have, such as a basement, attic, or garage, you could save some money overbuilding or buying a new stand-alone structure.  

 

How do you build a mother-in-law suite?

Building a mother-in-law suite takes forethought and planning, as you might expect.

Whether you are adding an addition to the main house, remodeling a garage or basement, or going all out and building a separate structure in the backyard, you will need to check codes and ordinances to determine what is and isn’t allowed in your area.

These zoning laws, occupancy codes, and even homeowner’s association covenants, conditions, and restrictions (CCRs) will dictate what you can do.

Once you have verified that your project is permitted, you will need to decide how much, if any, sweat equity you will put into the project or if you would rather pay to have someone else complete the whole task for you. 

As you prepare to start building, think about the future use of the suite, especially if you are making a detached unit.

For example, you may want to rent the team out, and having separate electricity, water, and gas run to the ADU will enable you to keep utilities separate from the main house.

That will also allow you to shut them completely off if the building were to be vacant for a while.   Keep your relative’s needs in mind when you are in the design stage.

For example, will doors need to be built to accommodate a walker or wheelchair? Do handrails need to be placed in the bathrooms? How about a zero-curb shower entrance? Thinking about the future can make a more seamless transition for your relatives down the road. 

 

What else can mother-in-law suites be used for?

Sometime in the future, your mother-in-law suite may become vacant. If so, there are various options that you can do with that space, regardless of whether it’s attached to the main house, built into the basement, or is an entirely separate structure.

In-law suites attached to the house can double as a backyard office, a long-term rental property (check your local codes). An Airbnb, a business endeavor such as a yoga studio or art studio, a home gym, nanny quarters, or even a commercial kitchen for a baking/cooking business.

A vacant, detached in-law suite could also be used as a she-shed or man cave; the possibilities are endless.

 

Do mother-in-law suites add value to my property?

Yes, mother-in-law suites can add value to your property, but it’s difficult to say precisely how much.

For example,  there are several variations of in-law suites, as described above, combined with varying finishes and amenities; this will all impact the value of your home differently. 

In addition, mother-in-law suites have been around since the 1940s; they have been challenging to track and even more difficult for appraisers and real estate professionals to place a valuation on because of a lack of suitable real estate comps.

So even though mother-in-law suites are continuing to gain in popularity, not every neighborhood has a house with an in-law suite that can act as a suitable comparable sale when determining your home’s value.

However, you can also look to national averages to get a ballpark figure. For example, a basement can increase a home’s value by nearly $50k, whereas adding another master suite to your home can increase your home’s value by $80k on average.

Nonetheless, the value your home gains from adding a mother-in-law suite will largely depend on your area and what type of addition you make to your home.

Ultimately, either as the buyer of a multi-generational home or as the seller, you will have to assess the value of having or building an in-law suite.

As a seller, you must realize your home won’t appeal to everyone, especially if you have converted one of two garage spaces into a mother-in-law suite when your neighborhood typically offers at least a two-car garage.

On the other hand, if you build out the back of your home to accommodate a family member, that additional living space can increase the overall value of your home and be attractive to buyers when you go to sell.

Lastly, there is also the personal value the extra space provides while you are the one using it. Whether it’s for housing elderly relatives, guests who come for frequent visits, or a recent college graduate, there is a lot of value to be gained beyond money from adding a mother-in-law suite to your home. 

 

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