English cottage garden.

Some mother-in-law suites are a detached structure that is fully functional on its own. (Getty Images)

A mother-in-law suite is a private living space that is either attached or separated from a larger home but on the same property. As the name suggests, it can be used by the parents of the homeowner, allowing multiple generations to live on the same property while maintaining privacy and separate spaces.

Mother-in-law suites may also be called granny flats, secondary suites and guest or pool houses. They all fall under the more technical term of accessory dwelling unit, or ADU, which means the space is considered its own living space, complete with a separate entrance, full bathroom and kitchen.

Building an ADU or mother-in-law suite isn’t cheap, but there is potential for it to add value to your property, as long as you consider all the additional details involved.

Here’s what you need to know about mother-in-law suites and ADUs:

[Read: 22 Sustainable Building Materials to Consider for Your Home]

ADUs and mother-in-law suites come in a wide variety of styles. Here are some of the common types you’ll find, all with a separate entrance from the main dwelling:

  • Finished basement.
  • Attached addition to the home.
  • Apartment above garage (attached or unattached to the main house).
  • Converted garage (attached or unattached to the main house).
  • Detached structure that is fully functional on its own (referred to as a casita in some parts of the U.S.).

While a mother-in-law suite may imply a single reason for the additional living space, there are others that drive people to seek an ADU option.

“The two biggest motivations are rental income potential and multigenerational housing flexibility,” says Kol Peterson, an ADU expert and author of “Backdoor Revolution: The Definitive Guide to ADU Development,” based in Portland, Oregon.

Common reasons for building an ADU or buying a home with one include:

  • Multigenerational housing as a solution to child care or cost needs.
  • Multigenerational housing as a cultural norm.
  • Rental income opportunity.
  • Space for regular visitors.
  • Space for at-home work or hobbies.

Multigenerational housing is common among many cultures throughout North America, Europe, Asia and beyond. Adult children may be more likely to stay in the home longer, and aging parents may move in with their child’s family. Multigenerational options are also increasing in popularity as expensive housing keeps adult children at home longer, and as people seek alternatives to assisted living or nursing homes for aging parents.

In some cases, the suite is intended to be used by grandparents, but for extended visits as opposed to full-time living. “The grandparents plan on spending a month, two months here a year,” says Kerron Stokes, a Realtor with Re/Max Leaders in Centennial, Colorado.

In any of these situations, the separate entrance and living space affords the adult generations privacy and the ability to have time apart, while making time together easy and frequent.

Other uses, of course, can help a homeowner cover the cost of the mortgage. ADUs can be used as a source of rental income, either for long-term tenants who sign a lease or for short-term leases through services like Airbnb or VRBO.

If you’re planning to build a mother-in-law suite on your property, don’t expect to do it for cheap. In a study of the typical cost of ADU construction, Peterson notes the average detached new construction ADU costs $180,833, while the average basement ADU costs $185,833 and the average garage conversion is $142,000, based on reported numbers from 50 homeowners who built an ADU.

In addition to the cost of construction, the red tape associated with rezoning a property or obtaining the right permits may be prohibitive to your timeline and wallet.

“It used to be if you wanted to add a mother-in-law suite, you had to change your zoning,” says Kari Lundin, a Realtor specializing in the purchase and sale of duplexes with Keller Williams Realty Integrity Edina in Edina, Minnesota. She explains that a zoning change can be complicated, requiring a petition for change signed by neighbors and approval of the local planning board.

While some states on the West Coast and some cities in other parts of the country, including Minneapolis, where Lundin works, have passed legislation that makes it easier to either skip zoning changes or get new zoning approved, other parts of the U.S. still have plenty of red tape that can take both time and money to get approval to build an ADU.

[Read: The Guide to Home Renovations.]

An accessory dwelling unit of any form can add significant value to your property, but the increase varies widely based on where you live. If there aren’t many granny flats where you live, it can also be hard to have the property appraised to reflect the change in value because there aren’t other properties to compare it to that have sold recently.

“That would be like adding a 20,000-square-foot swimming pool to a property. The appraiser might say, ‘I don’t know that it would add value for anyone else, because I don’t know anyone who needs a 20,000-square-foot swimming pool,” Peterson says.

If you're struggling to figure out an estimated value of your property or seeking to convince a lender to finance your ADU construction, Peterson recommends factoring in the potential financial gain from renting the property. You may not be able to provide an appraisal showing value increase with an ADU, but you could show how rental income would make a positive impact.

Working with a real estate agent to find the right property can be helpful. Lundin specializes in working with buyers looking for duplexes, triplexes and quadplexes, often for investment purposes. She works with clients to make sure the potential cash flow lines up with the costs of the property – a detail she says buyers must consider when they're planning to live on a property and rent part of it to tenants.

To find a property where building an ADU is possible, Stokes recommends asking where ADU zoning is available. Many cities have specific zoning types designated to make it easy to construct an ADU, while others may have simplified the process of rezoning the property for the same purpose.

[Read: The Guide to Making and Accepting an Offer on a Home]

To capture the right buyer who’s willing to pay more for a mother-in-law suite, you have to be clear. “You have to be purposeful in marketing the space and its utilization,” Stokes says.

However, you want to be sure you don’t make any assumptions about who should buy the home. While some ethnic or religious cultures commonly embrace multigenerational housing, you can’t market specifically to those groups – doing so would be a violation of the Fair Housing Act, Stokes explains.

The Fair Housing Act protects against housing discrimination based on race, color, national origin, religion, sex, familial status or disability. The marketing of your home and ADU must be done carefully to ensure you’re not “inadvertently discriminating against the buyer in any way,” Stokes says, and he recommends working with a real estate agent who has experience selling such properties to make sure fair housing laws are followed properly.

Types of Roads That Can Have a Big Impact on Home Sales

The rule is "location, location, location" for a reason.

The urban view of  vehicle light trails on the road.

(Getty Images)

A homebuyer’s must-have list often includes a certain number of bedrooms, updated appliances and a garage or backyard. But one detail that’s sometimes overlooked is just outside the property lines – and it’s a major deal-breaker for many. The road your house is located on, backs up to or is even in the general vicinity of can have a significant impact on your quality of life as well as your home’s resale value and how long it takes for you to find a buyer. Before you buy your dream home on a busy street or near a railroad, consider how these roads and locations can become a major turnoff for future buyers.

Updated on Nov. 1, 2019: This story was published at an earlier date and has been updated with new information.

High-traffic road

High-traffic road

The urban view of  vehicle light trails on the road.

(Getty Images)

Living off of a road that sees a lot of traffic throughout the day can make for a hassle getting in and out of the driveway. And when you decide to sell, potential buyers will worry about its resale value, says Greg Hague, CEO of Hague Partners and 72Sold.com, real estate brokerages based in Scottsdale, Arizona. “The biggest detractor in home values (on a busy road) is the fear that buyers have that these homes will be harder to sell,” he says. It might take more time on the market and a lower asking price to entice buyers over a similar home on a quieter street.



Aerial view looking directly down on a cul-de-sac in a planned exclusive residential community in the Scottsdale area of Arizona.

(Getty Images)

A cul-de-sac is a dead-end road with only one entrance and exit to other streets, and on residential streets it often includes a circle for cars to turn around. Often located deep within a subdivision or at the end of a neighborhood, a cul-de-sac means minimal traffic, which will be a big selling point down the line. The farther inside the neighborhood you go, the less traffic you’ll experience and the more desirable the houses typically become, explains Roberta Parker, a real estate agent for Berkshire Hathaway HomeServices Fox & Roach, Realtors in Princeton, New Jersey. A cul-de-sac may also back up to a wooded area or undeveloped land, so homeowners benefit from the added privacy of having no neighbors behind them. As Parker says: “A cul-de-sac is your best investment.”

Dirt road

Dirt road

One of the streets of the village of Tsevlo in the Pskov region

(Getty Images)

Some people prefer to get away from heavy traffic so much that they’ll leave pavement altogether. A dirt or gravel road will certainly attract fewer cars, and properties on a dirt road are often larger with more land. While a buyer should expect his house and car to be dirtier because of the dust or mud of the road, many homeowners consider it a fair trade-off. “We don’t really find that that is a detractor in value – it’s a lifestyle,” Hague says. While you may not have the same size buyer pool for your house as a home in a developed subdivision, you shouldn’t have to worry about would-be buyers seeing your dirt road as a negative in terms of home value.

Near a traffic light

Near a traffic light

Traffic light on red, Manhattan, New York, America, USA

(Getty Images)

Even if your area doesn’t experience high traffic volume throughout the day, having a traffic light within eyesight of your home can be irritating. Timothy Somers, a real estate appraiser and partner at the appraisal firm Davis M. Somers Co. in Ann Arbor, Michigan, lives near a traffic light. For him, it’s the noise from idling cars at the red light that can be a bit bothersome, although he’s gotten used to it over the years. “It can get noisy at times – not so much the traffic, but the loud music and that sort of stuff is annoying,” he says. Potential buyers may feel that way too.



Stunning sunset of famous posh residential area in Jiyugaoka, Tokyo, Japan.

(Getty Images)

An alley is a narrow street between buildings, often in a city setting, that may not even be marked on a map. But in older cities and historic districts, you may occasionally find property addresses that take you to a door in the alley rather than on a main street. It may be hard for visitors or potential buyers to find, but Hague explains an alley entrance is considered a plus for home value: “You obviously have no traffic – just foot traffic. It’s unique, and people like unique.” The feeling of privacy and exclusivity can play up the desirability of the home and make a buyer willing to pay more for it.

Double yellow line

Double yellow line

Asphalt road with yellow double line

(Getty Images)

The area might not seem busy if you visit on the weekend, but if the home is located on a two-lane road with a double yellow line to prevent cars from passing each other – most often found in less-populated suburban or rural areas – Parker says it’s a red flag that a lot of cars use the road. “A double yellow line is an indication that there is more traffic, and it’s not typical of just a neighborhood. A double yellow line is a serious road,” she says. Expect it to be difficult to turn left out of your driveway during peak traffic hours. Also expect speeds higher than 25 miles per hour, which may make spending time in the front yard feel unsafe if you have pets or young kids.

Highway within sight

Highway within sight

Multiple Lane Highway

Pete Farrington/EyeEm/Getty

Regardless of how far you travel to work, a home next to an on-ramp is not ideal due to the noise pollution and the difficulty you’ll have trying to sell it in the future. It's better to live in a neighborhood that is set up to provide easy access to commuting options and where you won't have to see or hear traffic from a highway.



train passes a crailway crossing by night at route 66

(Getty Images)

With a railroad near your home, you have a whole new type of car to be concerned about. Trains are loud to begin with, and if you live near a tunnel, train station or railroad crossing, expect even more noise as conductors sound horns and bells to ensure the track is clear. “Some people would shy away from a location like that. … When a freight train rolls through, it clanks, and there’s horns and more noise,” Somers says. If you’re considering buying a house near a railroad track, find out how often it’s used and the times of day trains will pass by. A regular midnight freight train could keep you up at night in your new home.

Brick or cobblestone paving

Brick or cobblestone paving

Stone street

(Getty Images)

A brick or cobblestone street often comes with the assumption that the houses on that street are as old as the paving. You may even live in a historic district of your city or town. “They’ve kept that (paving) because it has a such a historic and a kind of cool feel,” Hague says. A well-maintained house on a historic street will attract many potential buyers willing to pay top dollar for the location and overall look. Living in a historic district also means you’re expected to maintain your home to historic standards, so you’ll likely need to seek approval to paint your house, renovate the kitchen and even update the plumbing. All of these projects are likely to be more expensive for historic houses, as you may need to hire contractors with experience working on historic properties.

Corner lot

Corner lot

Typical family house neighbourhood in downtown Toronto. Fall season, no leafs on the trees, sunny day.

(Getty Images)

Attitudes about corner lots within a neighborhood can vary depending on an individual’s preference, but Somers says preferences have evolved to favor interior lots. “Corner lots back in the ‘50s and ‘60s were a premium site. Today people will steer clear of them; they don’t like them as well,” Somers says. “Because of the yard configurations, they usually end up with a small backyard and large side yard. It’s less appealing than the standard interior lot. Plus, they’ve got twice the sidewalk to shovel.”

One-way street

One-way street

Photo Taken In United States, Sapulpa

(Getty Images)

One-way streets are often found in more urban settings and often close to downtown to reduce gridlock. While it might prove inconvenient at times to live on a one-way street when you’re running late and need to head in the opposite direction, people don’t seem to let it affect their preference. Somers says he doesn’t see any change in desirability for a property located on a one-way street. So don’t be concerned about attracting potential buyers – the appeal of living close to downtown will likely outshine any downsides of living on a one-way street.

Types of roads that could affect your home value:

Types of roads that could affect your home value:

This is a picture of a cul de sac

(Getty Images)

  • High-traffic road.
  • Cul-de-sac.
  • Dirt road.
  • Near a traffic light.
  • Alley.
  • Double yellow line.
  • Highway within sight.
  • Railroad.
  • Brick or cobblestone paving.
  • Corner lot.
  • One-way street.

Read More

Tags: real estate, housing, housing market, home prices, home improvements, investing, renting

Devon Thorsby is the Real Estate editor at U.S. News & World Report, where she writes consumer-focused articles about the homebuying and selling process, home improvement, tenant rights and the state of the housing market.

She has appeared in media interviews across the U.S. including National Public Radio, WTOP (Washington, D.C.) and KOH (Reno, Nevada) and various print publications, as well as having served on panels discussing real estate development, city planning policy and homebuilding.

Previously, she served as a researcher of commercial real estate transactions and information, and is currently a member of the National Association of Real Estate Editors. Thorsby studied Political Science at the University of Michigan, where she also served as a news reporter and editor for the student newspaper The Michigan Daily. Follow her on Twitter or write to her at dthorsby@usnews.com.

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