Mother in Law Apartments or ADUs

Basements make excellent MILs

If you have some spare space in your home, say in the basement, you may have the opportunity to create a ‘Mother-In-Law’ (MIL) apartment, or more technically called an Additional Dwelling Unit (ADU), for extra income. The City of Seattle defines ADU as “a room or set of rooms in a single-family home in a single-family zone or a rowhouse or town­house in a lowrise zone that has been designed or configured to be used as a separate dwelling unit and has been authorized/established by permit.”                                              An ADU will usually consist of a kitchen, bathroom and living area and possibly additional room(s) for sleeping.

The rules for establishing an ADU are slightly different if the property is in a single family zone or lowrise zone. This is not the complete list, just some of the highlights:

  • Either main house or ADU must be occupied by the owner, as a principal residence.
  • The City will have the owner sign a certification of owner occupancy
  • Limit for ADU size is 1000 square feet in single family zoning , 650 in lowrise zoning
  • The sleeping area must have one operable window or exterior door approved for emergency escape or rescue
  • The ADU must meet current standards of the Seattle residential, building, mechanical, electrical and energy codes as required
  • One off-street parking space may be required for the ADU. This is not a requirement in lowrise zoning and in urban centers or villages

To establish an ADU the City requires plans and a permit, as well as a separate electrical permit. Further questions or want more detail? Contact me anytime!

Does your home already have a MIL/ADU? Did you know that if you simply have another kitchen and bathroom with living area in your basement it could be defined as an ADU? Do you know if your ADU is legal? You can check for previous permits with the City.

If it was not permitted, then it is ‘illegal.’ Don’t panic!  The way the city enforces violations is through complaints. It’s unlikely your neighbors will complain about your ‘other’ living area if it is not being rented out. Many residences in Seattle have ‘illegal’ ADUs.

If you would like for it to be legit and have the opportunity to rent it out, obtaining a permit is not difficult provided the ADU meets current standards.  Alternatively, there are some simple changes you can make to cure an illegal ADU such as removing the stove and removing locks that separate the two areas.

Why does The City care?  The rule is that with an ADU the property must be owner occupied, this is whether or not you have tenants in the ADU. Remember the City has you sign a certification of occupancy if you establish an ADU. I believe this is to stop people from renting out the property like a duplex – two separate units to two separate groups.  If the owner is not occupying the property there is more of a chance the home will not be maintained. ADUs are intended to bring more affordable housing options to our neighborhoods, not to bring their quality down.

There is also such a thing as DADU, a Detached Accessory Dwelling Unit, such as an apartment over a detached garage. I will post on those tomorrow.