How Can I Stop My Neighbor from Building a Mother-In-Law Suite?

What to do when your Oregon neighbor plans to bring in more neighbors.


I received a letter in the mail from my neighbor informing me that she intends to build an “accessory dwelling unit” on her property. We live in Oregon. From the letter, it sounds like the accessory dwelling will be a new house that can be rented to a third party.

My quiet neighborhood is composed of mostly families. I am concerned that the new dwelling on my neighbor’s property will be rented to young, rowdy people. What can I do to stop my neighbor from building the new dwelling on her property?


Let’s start with a very brief background on accessory dwelling units (“ADUs”). An ADU, also called a “mother-in-law suite” or “granny flat,” is a separate, complete dwelling unit. It can be either attached or detached from the primary dwelling unit (in this case, that would be your neighbor’s home).

ADUs are normally significantly smaller than the primary dwelling. In some places in Oregon, for example, the ADU can be no larger than 33% of the primary dwelling.

In cases like this, it's a good idea to make sure you are fully informed about all aspects of the pending land use application. Review all communications, including your neighbor’s letter, about the proposed ADU.

You should also contact your local planning department to get other important information. Some things to know that may help you challenge the proposal include:

  • who to direct your concerns and objections to at the planning department
  • any applicable deadlines, including deadlines to file written objections
  • whether a community meeting or public hearing has been scheduled
  • what approval criteria apply to the ADU application (the approval criteria are the requirements your neighbor will need to comply with to have the ADU approved), and
  • details about the actual ADU, including its proposed size and location.

It is also a good idea to become familiar with the applicable zoning ordinance. In Oregon, land is classified into different zoning districts, like residential or commercial. Residential neighborhoods are often classified into subzones like “Urban Residential-Low Density” or “Urban Residential-High Density.” The applicable zoning ordinance will dictate what uses are permitted in each zone. For example, the ordinance may allow ADUs in “Urban Residential-High Density” zones, but prohibit such use in the “Urban Residential-Low Density Zone.” If ADUs are not permitted in your zone, you will have a strong argument for why the use should not be approved.

To have any chance of stopping a development project like an ADU, you need to make sure to timely file your objections. Objections that might be considered valid include, but are not limited to:

  • ADUs are not permitted in the applicable zone
  • the proposed ADU is too big, and
  • the proposed ADU will violate setbacks (in other words, it will be located too close to the property line).

If the project is ultimately approved, you are not necessarily out of luck: You might be able to file an appeal. Immediately after the ADU is approved, check with your local planning department to learn about the appeal process and what you need to do to file an appeal. At a minimum, you will need to submit a written appeal and appeal fee. And again, be ready to comply with all applicable deadlines.

Retaining a land use attorney is a good idea to help make sure deadlines are met and that you put your best argument forward at the beginning of the process.

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