Is Your Basement ADU-Ready? The 7-Point Checklist (Plus a Bonus #8)

Not every basement is a slam dunk for an ADU — but most hurdles have solutions. Use this quick checklist to see if your space is on track, and what you can do if it’s not.

1. Ceiling Height

What to check: At least 7' clear over most of the space. Watch for beams and ductwork.
Solution: Expose joists, lower the floor in one area, or reroute ducts. A good contractor can usually find a few extra inches.

2. Emergency Egress

What to check: Each bedroom needs a window or door that leads directly outside.
Solution: Add an egress window well or widen an existing window. Many cities even publish pre-approved window well details.

3. Separate Entrance

What to check: A walk-out, side door, or a spot to add one.
Solution: Convert a side yard access, add an exterior stair, or rework an existing patio door into a private entry.

4. Kitchen + Bath Space

What to check: Even a small ADU must have both.
Solution: Galley kitchens and compact 3-piece baths (shower, sink, toilet) often fit into tighter layouts. Consider stacking plumbing near existing lines to cut costs.

5. Moisture / Waterproofing

What to check: Look for leaks, musty smells, or past flooding.
Solution: Add perimeter drains, sump pumps, or modern waterproofing membranes. At minimum, seal cracks and improve ventilation.

6. Utility Connections

What to check: Access to drain lines and room in your electrical panel.
Solution: Upgrade to a larger electrical panel, tap into existing drain stacks, or add a pump system where gravity doesn’t cooperate.

7. Fire Separation

What to check: Floors and walls between units often need fire-rated protection.
Solution: Install Type X drywall on ceilings/walls and add batt insulation. These upgrades usually boost soundproofing too.

Bonus 8. Parking Requirements

What to check: Does your city require a parking space for the ADU, or proof that transit is nearby?
Solution: Some jurisdictions (like Seattle) have eliminated parking requirements. Others may allow creative solutions like tandem parking in a driveway. Always check local rules early to avoid surprises.

Why This Matters

Instead of guessing if your basement is “good enough,” this checklist shows what’s missing — and how to fix it. A few smart upgrades now can save you costly rework when the city inspector shows up.

What’s Next?

If your basement passes the test (or you now know what to tackle), the next step is permits and planning. We break it all down — from zoning basics to cost ranges and starter tools — in our Basement to ADU Starter Kit.