Is encroachment by a building onto a neighbor's land a trespass?

Yes, encroachment by a building onto a neighbor's land is considered a form of trespass. Trespass occurs when a property owner unlawfully enters or remains on another person's property, and an encroachment typically involves a physical structure extending beyond one's property boundaries. This can lead to legal disputes, where the affected neighbor may seek remedies such as removal of the encroaching structure or compensation for damages.