Civil Code § 1013
CHAPTER 1. Accession to Real Property [1013. - [1019.]]
When a person affixes his property to the land of another, without an agreement permitting him to remove it, the thing affixed, except as otherwise provided in this chapter, belongs to the owner of the land, unless he chooses to require the former to remove it or the former elects to exercise the right of removal provided for in Section 1013.5 of this chapter.