Adverse possession—sometimes called squatter's rights—occurs when a person or entity who does not own a certain piece of real property occupies or uses it in a way that is adverse to the owner of the property—meaning the use is in conflict or at odds with the property owner’s interests.

If this adverse possession or use of the property meets the legal standard for adverse possession—often described as use that is continuous, exclusive, hostile, open, and notorious—and continues for the prescribed period of time (usually specified in the state statute)—the person or entity adversely possessing or using the property will acquire ownership of the property (title). This ownership will result in the changing of boundary lines.

Because the required adverse possession must be open, obvious, and adverse to the owner’s interests, title may only be acquired by adverse possession to the portion of property that is used in that way.

Adverse possession laws vary from state to state and may be located in a state’s court opinions (also known as common law or case law) or, more often, in its statutes.

In New Hampshire, adverse possession laws allow a person to claim ownership of property not originally their own if they possess it in a manner that is continuous, exclusive, hostile, open, and notorious for a period of 20 years (New Hampshire Revised Statutes Annotated (RSA) 508:2 and 508:3). The possession must be obvious to anyone, including the owner, and it must be without the owner's permission. The claimant must treat the property as their own, to the exclusion of the true owner, and their use of the property must be in conflict with the owner's interests. If all legal requirements are met over the two-decade period, the individual may be able to acquire legal title to the property. It's important to note that adverse possession is a complex area of law, and those who believe they have a claim (or property owners who are contesting a claim) should consult with an attorney to understand their rights and obligations under New Hampshire law.