My aunt and uncle had a house like this - the lot sloped down from the street, so from the street it looked like a one story house, and the main story had living, dining, kitchen, master suite, and guest room, but then there was a downstairs with two bedrooms, additional bathroom, and big 70's rec room (also laundry and storage and patio access). This arrangement worked great when my cousins were kids - it was tons of fun when we visited because we had our own space down in the rec room. What made this house work was that you entered on the main level, it was five steps from the carport entry to the kitchen (no carrying groceries upstairs - but then again I used to love on a second floor walk up and it was fine), and the grownup bedrooms were on the main floor, leaving the downstairs as a dedicated kid zone. I really liked the division of spaces.

Your septic was permitted with a certain number of facilities in mind. In a certain location. Double inlets is usually frowned on. It’s not just about tank capacity. The building site has to be master planned for it all to work. It must be sited for gravity draining to work. “Just” adding an ADU that wasn’t accounted for in the original property layout and septic design for the house’s location will require its own system. If there is room. If there isn’t room for another septic? No ADU will be allowed. Contact your septic permit issuer. You’re not gonna park an RV as a dwelling. Not a chance.

Hi, Does it make sense to build a second story above the garage and turn that into an ADU (~600 sqft)? This would require re-inforcment of the foundation. - doing this will also leave our driveway alone and we wouldnt have to relocate the Approach, Water Meter, and pour concrete on around 1600Sqft of space. Redlines indicate where everything would have to be excavated and re-done Concerns are 1. Cost, 2. Ease of build / timeline (We are ready to submit the third time to the city with all the updates, making a second story plan now would mean to resubmit from beginning + cost of redesign) Green lines in second image would be a second story above the garage and new front addition.

You are going to need to go to your local builing inspector office. Don't guess at X feet away from trunk, or guess a thumb of X with the canopy- or maybe guess it's a drip line thing. Don't guess. Your local ordinances and regulations will direct if you can build by that tree, and what you can build. We here can't really guess your local ordanances for you. You seem to be guessing at what your ordanances might be at this point because of other people guessing. At the same time you can find out what size or footprint of house your municipality will allow in that spot. take your map in and let them guide you.