10/19/2026
Scared that adding a backyard ADU will trigger a full tax reassessment on your primary California home? Here is how state tax law actually works! 📑🏠
Good news: under California tax law (Proposition 13), building an ADU does NOT reset the assessed value of your main primary residence! Instead, the county tax assessor performs a blended assessment—adding tax value only for the newly constructed square footage based on its cost or market value, while keeping your existing primary home's low tax base locked in place.
This blended assessment structure means you get to add massive property equity and collect monthly rental cash flow (or house family members) without suffering a massive spike in taxes on your original home.
Want to see how county assessors calculate ADU taxes and estimate your exact tax impact before you build?
👇 Comment "TAX" on this post, and our automated system will instantly DM you the link!