[jyl]

"There’s some relief if you're worried about losing your Prop 13 tax base. Under current rules, you can rebuild up to 120% of your original home's value without triggering a reassessment. As a result, you can improve materials or add a bit more space without worrying about taxes going through the roof."

https://www.benzinga.com/real-estate/25/01/43099347/do-l-a-wildfire-victims-still-pay-property-taxes-and-mortgages-on-homes-that-burned-down-heres-what-you-need-to-know

Maybe not the most definitive source but I expect they have it right.