This section defines what “new construction” or “newly constructed” means for real estate purposes. It includes any additions or major changes to property since the last tax lien date, such as adding new features or changing how the property is used. If renovations make a piece of property like new, it's considered major rehabilitation.

However, if property was damaged by disaster and is rebuilt to be nearly the same as before, it’s not considered new construction. Repairs to underground storage tanks to comply with regulations are also not considered new construction, provided the repairs only bring the property to its previous state.

This section deals with property tax relief for properties that are severely damaged or destroyed by a disaster declared by the Governor. If you rebuild on the same site within five years, under certain conditions, you might keep the original property's tax base value.

The new property must be similar in size, use, and function to the original. If the value of the new property surpasses 120% of the old property's value, the excess is added to the old tax base value.

If your property was affected by specific fires in 2018 or from 2024 to early 2025, you have an extended period to apply this relief.

This law specifically applies to properties damaged after January 1, 2017.

When a part of a property is newly constructed, the tax assessor will set a new base value for just that part. The base value for the rest of the property doesn't change. If the new construction isn't finished by tax day, its value is assessed as it progresses each year until it's complete. Once finished, it's given a new base value based on its full updated value. In-progress construction doesn’t get a permanent value until finished.

This law requires that whenever a building permit is issued, a copy must be sent to the county assessor quickly. Similarly, when a certificate of occupancy or any document showing the completion date of new construction is finalized, it must be sent to the assessor within 30 days.

When building plans are submitted, a scaled floor plan must also be provided to the assessor, detailing the building's size and intended room uses. This can be in electronic form if available. For multiple units built from the same plans, only one set of plans is necessary unless a unit's square footage changes, in which case an updated plan is required.

Additionally, county supervisors can decide that any tentative maps and conditions of approval filed for building projects must be submitted to the assessor promptly, potentially in electronic form if possible.

This section makes it clear that constructing or adding active solar energy systems to a property isn't considered 'newly constructed' for tax purposes. An active solar energy system collects, stores, or distributes solar energy and doesn’t include solar pool or hot tub heaters. Systems can heat water, condition space, generate electricity, and provide process heat or solar mechanical energy. The law provides a tax exclusion for these systems, including their parts, storage, and certain dual-use equipment up to a specified value. New buildings with solar systems are eligible for this exclusion if the owner-builder hasn't claimed it and sells the building before reassessment. The exclusion applies until a change in ownership and covers fiscal years 1999–2025, ending January 1, 2027. Qualifying systems continue to be excluded after this date until the property is sold.

This law section clarifies that construction related to fire safety isn't considered 'new construction' for tax purposes if it took place after November 7, 1984. This includes systems like fire sprinklers, fire detectors, and upgrades to fire exits. The law defines these terms: a fire sprinkler system releases water during a fire, while other fire systems might use chemicals. Fire detection systems include alarms that alert people of fires. Egress improvements provide ways to leave a building safely during a fire or make it safer for those who can't leave. These rules apply only to existing buildings.

This California law explains that improvements made to a home to make it accessible for a severely and permanently disabled resident do not count as newly constructed for property tax purposes. This means you won't face higher property taxes just because you modified your home for accessibility. However, only changes specifically aimed at improving accessibility, like adding ramps or widening doorways, are excluded from tax calculations—general renovations aren't covered. To qualify, a doctor must confirm the resident's disability and the need for these improvements, and documentation must be submitted to the tax assessor. The assessor may charge a fee to process these documents. This law applies to changes made after June 6, 1990.

This section explains that for property tax purposes, new construction doesn't count the costs of seismic retrofitting improvements when it's part of an existing building. Seismic retrofitting covers work done to reduce earthquake hazards by strengthening buildings and making them safer during earthquakes. Such work doesn't include unrelated updates like new plumbing or electrical systems.

Property owners must certify which parts of their construction project are related to seismic retrofitting and report costs to the county assessor. To claim a tax exclusion, owners must notify the assessor either before or shortly after project completion and file the necessary paperwork within six months.

Additionally, certain masonry buildings with prior exclusions will continue to benefit after a 15-year period unless there's a change in ownership.

This law clarifies that making changes to an existing building to improve access for disabled people is not considered 'new construction' under certain tax assessment rules. If you remodel a building to make it more accessible, like adding ramps or widening doorways, it won't affect property taxes as new construction would, unless that building already benefits from another specific exclusion. However, building an entirely new structure or adding a new addition is not covered by this exclusion.

To qualify, you must notify the assessor within a specific timeframe and submit required documentation, detailing the changes for accessibility. The modifications should comply with the Americans with Disabilities Act and current California Building Standards. This provision has been in effect since June 7, 1994.

This law section explains that when a structure is substantially damaged or destroyed due to environmental cleanup on contaminated property, rebuilding it doesn't count as 'new construction' for property tax purposes if the new structure is similar in size, utility, and function. The damage is considered substantial if it exceeds 50% of the property's value before the damage.

The replacement must be similar in function, subject to similar zoning laws, and not exceed 120% of the value of the original structure. Owners must apply for tax relief, proving they didn’t contribute to the contamination and that the property is officially recognized as a contaminated site. Notifications and necessary documents must be submitted within specific deadlines following the completion of construction, which applies to projects finished after January 1, 1995.

This law states that adding or constructing a system to capture rainwater does not count as 'new construction' for tax purposes. These systems are designed to collect rain off roofs or hard surfaces for use later. If someone builds a rainwater system when constructing a new building they don't plan to use themselves, it still doesn't count as new construction. The initial buyer of such a building can claim tax benefits, but only if the builder hasn't already done so and if the purchase happens before the building is reassessed. Buyers must provide paperwork to the assessor to determine the system’s value and any rebates received. This provision applies only to construction finished from January 1, 2019, and is valid until January 1, 2029.