Total Cost of an ADU

3 Replies

Going to build an ADU (800 total square feet) next to a house that has a basement and a second floor.

Question is, which costs more:

1) Building a second floor (roughly 400 sqft foundation and 400 sqft second floor).

Or

2) Build a basement (roughly 400 and 400 again).

I realize there are many factors (sewer slope in basement, soil removal, etc.), I was just curious about general cost (2nd floor wood vs basement concrete).

Any thoughts on the matter are greatly appreciated!

@Doug Kienzle - you have an expert right in Portland, OR. Check out http://www.buildinganadu.com/c... if you haven’t done so yet. It might help you estimate costs.
If you are looking for more info than that, there are some other sources like https://www.hausable.com/ (California specific) that offer ADU consulting services to answer these types of questions. Good luck with your search and your future project.

@Doug Kienzle

Don't forget to take property taxes into account

Around hear( Cook County, IL) anything below grade would not be factored into assessed value. Thus lower your tax basis.