Reassessment of a property is required any time new construction occurs (Section 71, Revenue and Taxation Code). Thus, new construction, when not considered normal maintenance or repair, is assessable if it adds value to the property. The market value (not necessarily the cost) of the addition or other "new construction" is determined by the assessor and added to the existing property assessment. The value of the existing property is not affected.
New construction that adds value to the property represents the incremental value added to the existing property and will generate a supplemental assessment. The previously existing property, however, is not reappraised; its assessed value will not change except for the annual inflation adjustment of up to 2%.
It is important to note that the county assessor, by law, is required to value all new construction, even if a building permit has not been issued. However, not every building permit for new construction results in reassessment. In general, the Placer County Assessor’s Office processes thousands of building permits annually, yet less than half result in supplemental assessments.