Accessory Dwelling Units: What Homeowners Should Know

1. What is an ADU?
2. Who Benefits From An ADU?
3. Start by Checking Your Local Zoning Laws
4. Plan for Utilities & Sewer / Septic Tie-Ins
5. Design for Privacy & Access
6. Know the Costs
- How Construction Solutions, Inc., Can Help
Helpful References for New England Homeowners Looking to Build an ADU:

It’s not surprising that Accessory Dwelling Units (ADUs) have become a popular option with a nationwide shortage of affordable homes, a high cost of living, and skyrocketing interest rates.

There are 42 million renters across the U.S, with over 21 million renters considered cost-burdened, spending more than 30 percent of monthly income on housing costs. That represents almost half (49.7%) of all renters.

That cost burden does not account for other necessities such as food, health insurance, child care or clothing. Additionally 18.8 million homeowners are spending more than 30% of their monthly income on home costs. Creating a large population of cost-burdened homeowners.

Although regulations vary from state to state for building AUD’s, currently more states are adopting more favorable regulations as a way to help ease housing shortages.

Rental cost burdened households by race, asian 1 million; white 10.4 million; Indian or Alaskan 229k; native Hawaiian 53k; two or more races 2.8 million; hispanic 4.8 million

Property owners across New England have been utilizing ADU’s for additional income, home offices, multigenerational living, and as a way to increase living space and property values. Massachusetts recently passed state legislation, which overrides local zoning for discretionary permits. Thus AUD’s are now the owners right to build, as second living space in a single family dwelling zone.

Local municipalities still dictate septic requirements, property setbacks, site plan reviews, and if the property can be used as a short term rental.

Here’s what you should know if you’re thinking about adding an ADU.

1. What is an ADU?

An ADU is a smaller, self-contained living space on the same lot as a primary home. They are off referred to as in-law suites, garage apartments or backyard cottages. The ADU must have a separate entrance from the primary dwelling, either through a common hall or entry way, or an outside access.

Common examples include:

Finished basements or attics with separate entrances
Detached Units, such as a cottage or tiny home
Garage conversion or upper level garage living quarters
Additions to existing dwellings

ADU diagram showing detached unit, attached unit, upper level unit, interior lower level unit, above garage unit, garage conversion; Accessory Dwelling Unit

2. Who Benefits From An ADU?

rental income sign for accessory dwelling unit income for property owners

Both tenant and property owners benefit:

Rental income for property owners
More options for older adults to have a caregiver live near by, but still maintain privacy
Affordable rental costs for tenants
Multi-generational family units, allows older parents to downsize, stay in their neighborhood, as their grown children raise a family in the home they grew up in
Snow bird affordability to keep an affordable rental where they have roots
Some tenant and property owners make arraignments for assistance with upkeep and maintenance with tenants to lower rent, and help the homeowner share in the upkeep of a yard & maintenance

3. Start by Checking Your Local Zoning Laws

Each state has has different rules for ADUs. Many communities now allow them to boost housing options, but you’ll still need to check your state and local towns bylaws.

The requirement fall into a few categories:

Minimum lot size requirements
Maximum ADU square footage
Parking and setback regulations
Owner-occupancy requirements
Utility hook ups for water, sewer, electricity, and heating source

Some towns require a special permit — so always confirm before you start designing.

red checkmark in front of government symbol; ADU regulations

4. Plan for Utilities & Sewer / Septic Tie-Ins

utility tie ins for ADU; gas, water, electricity, wifi symbols shown over a house

Your new ADU will need proper connections for water, sewer (or septic), electric, and possibly gas. In rural areas, your existing septic system may need an upgrade to handle the added load.

Even if you plan to use the space for yourself now, plan for the option of a rental for the future by separating meters. Working with an experienced contractor helps you avoid surprises.

5. Design for Privacy & Access

A well-planned ADU should feel separate but connected. Things you need to consider while planning:

A design that complements your residence
Separate entrances and walkways
Soundproofing for attached units
Shared vs. separate driveways
Good lighting and security
Consider the features you will incorporate
Design functionality and flow of the living area
Storage options, including yours, if utilizing a current basement, attic or garage
Consider the soil conditions and your properties grade if adding an addition or new structure.

two family brick house door entrances next to each other for in-law apartment verses a tiny home

Pro Tip: A smart layout makes the space more comfortable for property owners and tenants.

6. Know the Costs

lot planning drawing, calculator and pen for Accessory Dwelling unit building

Building an ADU isn’t cheap, but it’s often more affordable than buying a bigger house. Costs will vary depending on your design and needs.

Many homeowners recover costs over time through long-term rental income and increased resale value. It’s important to work with a reputable contractor to address your needs and evaluate your site.