Final answer:
In jurisdictions where the doctrine of adverse possession is not allowed or limited, the outcome of a situation where an owner builds an encroachment and no one finds out for 20 or 30 years can vary. Tearing down the structure may not be the only solution, as the legality can be determined by a court decision and the neighboring property owner may or may not gain legal ownership.
Step-by-step explanation:
When an owner builds an encroachment by mistake and no one finds out for 20 or 30 years in jurisdictions where the doctrine of adverse possession does not exist or is curtailed, the outcome can vary depending on the specific laws and regulations of that jurisdiction. Generally, tearing down the structure may not be the only solution. The legality of the structure can be determined by a court decision, and the neighboring property owner may or may not gain legal ownership. It is important to consult with a legal professional to understand the specific laws and options in your jurisdiction.