Frequently Asked Questions
An Accessory Dwelling Unit (ADU) is a compact, self-contained home situated on the same property as a primary residence. ADUs can be detached or attached to the main structure.
- Detached ADUs are sometimes called DADUs, granny flats, or laneway houses. They can be single-story, or they can be nested above a garage.
- Attached ADUs are often called mother-in-law units, secondary suits, or English basements. They can be a newly constructed addition or a basement or attic conversion. The building code considers attached ADUs to be duplexes.
In Grand Rapids, an ADU’s maximum size is 850 square feet, though this may decrease for detached ADUs, which are classified as accessory structures with additional size restrictions.
Additionally, an ADU cannot exceed 40% of your primary structure’s square footage. For example, a 2000 sq ft home allows an 800 sq ft ADU, while a 1500 sq ft home permits 600 sq ft. The minimum size is 400 sq ft, even if your primary home is smaller than 1000 sq ft.
Additionally, an ADU cannot exceed 40% of your primary structure’s square footage. For example, a 2000 sq ft home allows an 800 sq ft ADU, while a 1500 sq ft home permits 600 sq ft. The minimum size is 400 sq ft, even if your primary home is smaller than 1000 sq ft.
As of April 23, 2024, it’s legal for all single-family and two-family homes to have one ADU per property.
Properties with flat backyards are typically the best candidates. If you have at least a 25’ x 35’ open space, we can usually find a solution that works. Alternatively, an unused garage, an unfinished basement, or even an attic can be great options for conversion.
Properties with flat backyards are typically the best candidates. If you have at least a 25’ x 35’ open space, we can usually find a solution that works. Alternatively, an unused garage, an unfinished basement, or even an attic can be great options for conversion.
In most cases, yes. While adding an ADU won’t uncap your property’s taxable value, it will likely result in a proportional increase, as an ADU adds to your property’s overall value. If you want a rule of thumb, your property taxes will probably increase by about 30% +/- 10%, but this depends on your specific case. If you’ve owned your house for a long time and the taxable value is much lower than your SEV, it may be more on a percentage basis.
A more accurate calculation would be to assume it will add half the market value to your tax bill. So if it’s a $150k ADU, half would be $75k. Divide this by $1k and multiply it by your millage rate (33 mills for 100% principal residence Exemption (PRE) and 51 mills if you don’t live on the property. So $2475 if you live on-site and $3825.
Your PRE % will change a bit too. It might decrease by around 1/3 since the ADU wouldn’t be your primary residence. In that case, you’ll be somewhere between $2500 and $3825.
Note: These are all estimates. Your exact tax situation will vary. We can give you a more accurate, personalized estimate as we begin working together.
A more accurate calculation would be to assume it will add half the market value to your tax bill. So if it’s a $150k ADU, half would be $75k. Divide this by $1k and multiply it by your millage rate (33 mills for 100% principal residence Exemption (PRE) and 51 mills if you don’t live on the property. So $2475 if you live on-site and $3825.
Your PRE % will change a bit too. It might decrease by around 1/3 since the ADU wouldn’t be your primary residence. In that case, you’ll be somewhere between $2500 and $3825.
Note: These are all estimates. Your exact tax situation will vary. We can give you a more accurate, personalized estimate as we begin working together.
The cost depends whether you want an attached or detached ADU and how you’d like to configure your utilities. Do you want separate meters for each unit, or are you okay with sharing? Sharing is typically cheaper but less convenient. Additionally, are you using gas-powered appliances or opting for an all-electric setup?
- Sewer: Michigan Plumbing Code prohibits sewage from one building flowing through another, so if you want an attached ADU, you just use the same line. Otherwise, you can’t However, you may be able to connect to a line outside the house in your yard, avoiding the need for an expensive sewer tap.
- Water: Connecting to your existing water line is usually possible if your home’s water meter is accessible. This involves vertical drilling under your house, breaking up concrete around the meter, tying into it, and patching the concrete. If you prefer a separate water meter, you’ll need to pay for a new connection.
- Gas: DTE provides new gas meters in Grand Rapids, with fees typically based on the linear feet of the connection.
- Electricity: Consumers Energy installs new electric meters in Grand Rapids. Their fees depend on the distance of the connection, and they’ll need to know what appliances you’re using to correctly size your service.
We’ve been through all these processes many times and can guide you through them or handle everything for you.
- Aging in Place: Create a comfortable, zero-step space to stay close to family while maintaining independence.
- Downsizing: Transition from a larger home to a more manageable living space.
- Generate Income: Earn extra income by renting out the unit.
- Support Young Adults: Provide affordable housing for a young adult or recent graduate starting their career.
- Care for Family: Offer housing and care for a family member while avoiding the high costs of assisted living facilities.
Possibly, but it will require some investigation, and a structural engineer will need to be involved—unless you already have building plans.
While the idea sounds appealing, older garage foundations often weren’t designed to support the weight of a second story. If your existing foundation is suitable, the process becomes much easier. Either way, we’ll need to excavate to assess what you currently have and calculate whether it can support the added structure.
If you’re considering building a brand-new garage with an ADU above, the process is simpler because we can design the footings to handle the extra weight from the start.
While the idea sounds appealing, older garage foundations often weren’t designed to support the weight of a second story. If your existing foundation is suitable, the process becomes much easier. Either way, we’ll need to excavate to assess what you currently have and calculate whether it can support the added structure.
If you’re considering building a brand-new garage with an ADU above, the process is simpler because we can design the footings to handle the extra weight from the start.
Since ADUs are relatively new to the West Michigan area, many banks and credit unions may be hesitant to lend due to unfamiliarity with the product. However, we work with trusted partners who understand ADU financing and can connect you with the right resources to help you move forward confidently.