If you can afford the cost of the improvements, the chances of you being unable to pay X% (where X is likely a single digit) taxes on the value of those improvements is ... small.
Sure, Georgism has a lot to recommend it (more or less exclusively taxing land), but that's not happening in the US any time soon.
Also, notice that most property tax assessments are based on purely physical exterior-visible aspects of a home. If you convert that rats nest of a bathroom into a wondrous home spa, in most places no tax assessment change will follow.
Only if you don't file any permits, correct? I'm not aware of anywhere that won't reassess on major improvements. Which is partly why SF Bay area housing is so terrible - none of the owners want to trigger a reassessment, as in many cases it may increase their tax bill 10x.
I just got the form from the county for this for some improvements to my house, so I can answer. Permits for "improvements" are sent on to the county tax assessor, and they send you a form basically asking for the value of the improvement. Note that "maintenance" doesn't count, only "improvements" (and then only specific improvements; e.g., adding solar doesn't count). The value gets added to your Prop 13 value, but does not trigger a complete reassessment. So it's unlikely that any improvement would result in a 10x tax bill increase, unless you've owned the property for a long time (meaning that your Prop. 13 value was significantly less than the real value of the property).
The property I’m currently renting has an assessed value of $248k. A nearby comparable house just sold for $2m. It’s not unusual around here for that to be the case.
I have not lived in any municipalities where doing remodelling that doesn't chnage the number of rooms or enlarge the total footprint of the built area would change tax assessment.
SF is not going to tax your house more because you went from Home Depot subway tile in the bathroom to Murano hand made glass from Italy, whether you file a permit or not. One of my children just had their house electrical system upgraded from knob&tube to contemporary romex, all under a permit, and I don't believe it will have any impact on their property taxes whatsoever.
If you did in fact add a room or enlarge the building, then it's worth more and will/should be taxed more, no? The taxes represent a small additional part of the total cost of the changes, spread out over years.
FYI - the house I’m renting, if it got reassessed at market rates, would go from $3600/yr in property taxes to $23000/yr in property taxes. Which for all but the most lavish upgrades would swamp the cost of the upgrades pretty quickly.
California Prop 13 causes some serious market distortions.
Sure, Georgism has a lot to recommend it (more or less exclusively taxing land), but that's not happening in the US any time soon.