A mother-in-law unit is often integrated into the main house. That means it may not have its own entrance like other ADUs. The square footage of an ADU is not added to the square footage of the main house. Most mother-in-law units are part of the overall house and added to its square footage.
ADU stands for Accessory Dwelling Unit, sometimes called granny flats or mother-in-law apartments. The most common ADUs are smaller housing units built on the same site as a single-family home by converting existing structures (like a garage) or building new in the back yard.
An ADU is usually built in the backyard, where space may be limited. An in-law suite must be attached to the house and is typically built on the first floor. Consider where these structures would be placed on your property.
You may pay more for homeowners insurance after building a mother-in-law suite, and the value it adds to your home may increase its taxable value and your property tax bill.
A mother-in-law apartment (also called an in-law suite or granny flat) is a small, private living area within a family house. This area can be attached to the main home, usually in a walk-out basement apartment or as a first-floor attachment or stand-alone in the nearby yard.
Usually mother-in-law suites have their own bathroom, as well as a bedroom. Some may even have additional bedrooms, a small kitchen, and living room.
Other Names
They're more commonly referred to (on this site and in much literature on the subject) as accessory dwelling units, or ADUs, which is their legal and regulatory name. You may have also heard of them under other names, including: Accessory apartment. Basement apartment.
On average, an in-law suite can increase your home's value by 20% to 30%, depending on where you live and the quality of the addition.
Temporary Rental
Another way you can use an in-law suite is for Airbnb hosting. There are many requirements for an accessory dwelling unit (ADU) that you need to follow in order to qualify for renting, including providing amenities separate from the primary dwelling unit: Entrance/exit. Sleeping area.
Despite its specificity, the term “mother-in-law suite” is sometimes used interchangeably with “guest house.” That said, guest houses are generally detached from a primary residence, while mother-in-law suites may be attached to it.
An accessory dwelling unit, or ADU, is a unit with a full kitchen and bathroom that is accessory to residential. Also called a granny flat or second unit, it can be on a property with a home or apartment building. It can also be detached or attached.
Can An ADU Be Larger Than The Primary Residence? An attached ADU cannot be more than 50% of the size of the main residence. For detached ADUs, if the size exceeds that of the main house, it is capped at 800 square feet. ADUs are intended to be secondary in size to the main residence.
ADUs are considered an addition to a single-family dwelling, where they can be used for extended family stays or for rental income. They can be either attached or detached from the main house. On the other hand, duplexes are attached dwelling units for two families.
ADU stands for accessory dwelling unit. An ADU is an additional living area located on the property of a primary single-family residence.
Chances are, as a California resident, you've heard of backyard houses before, though you may not have heard them referenced under that name. The legal and regulatory name for backyard houses is accessory dwelling unit, or ADU.
An accessory dwelling unit (ADU) is a small dwelling on the same grounds as, or attached to, a single-family house. For example, it could be an apartment over the garage, a basement apartment, or a stand-alone house in the backyard. An ADU can be used to house a family member or for additional income through rent.
Commonly used physical descriptions of housing units that aren't preferential, such as “mother-in-law suite” or “bachelor apartment,” are acceptable because they describe the property and don't literally limit the buyers or tenants to mothers-in-law or bachelors.
The cost of building an in-law suite can vary widely depending on factors such as size, location, materials, and local labor costs. On average, it can range from $50,000 to $250,000 or more.
Building a mother-in-law suite could also offer certain tax benefits. How many square feet is a typical mother-in-law suite? Mother-in-law suites can vary in size but are typically about 500 square feet.
Constructing an ADU on your property typically increases the resale value of the property, since the house will be appraised with other homes with ADUs.
In-Law Suite
Converting a garage into a full in-law or guest suite—or a guest house in the case of a detached garage—costs $20,000 to $50,000 on average. At the lower end of the range, a basic conversion will include insulation, drywall, flooring, and a bathroom.
Generally, a mother-in-law suite has a bedroom, a full bathroom, a living space, and a kitchen. Ideally, it will have a separate entrance, for the convenience and privacy of the occupant.
A duplex is a multi-family home.
Expect to pay more for detached dwellings and room additions. Do you want to add an extra living space to your property for visiting family or potential rental income? The average cost to build an in-law suite has a wide range of $25,000 to $265,000 with an overall national average of $82,750.