Private nuisance protects a landowner's or occupant's use and enjoyment of property against interference caused by someone else's conduct on nearby land — noise, odor, vibration, smoke, light, water runoff, or similar intrusions that do not necessarily involve any physical trespass onto the plaintiff's property. Unlike trespass, which protects the right to exclude others from land, private nuisance protects the right to use and enjoy land without unreasonable interference, and it does not require the defendant to have entered the plaintiff's property at all.

It is distinct from public nuisance, which protects rights common to the general public (such as obstruction of a public roadway or a widespread health hazard) and is typically enforced by a government entity or by a private plaintiff who suffered a special, different-in-kind harm. Private nuisance is a private right belonging to the possessor of the affected land.

A plaintiff generally must show: (1) the plaintiff has a possessory interest in the affected land, (2) the defendant's conduct or condition caused an interference with the plaintiff's use and enjoyment of that land, (3) the interference was substantial, meaning more than trifling annoyance, and (4) the interference was unreasonable, judged by balancing the gravity of the harm to the plaintiff against the utility and social value of the defendant's conduct.

Nuisance liability can rest on intentional conduct, negligent conduct, or, in some jurisdictions, abnormally dangerous activity — it is defined by the result (unreasonable interference with land use) rather than by a single required mental state, which is one reason it is often pleaded alongside negligence or trespass claims arising from the same conduct.

Courts typically weigh factors such as the extent and duration of the harm, the character of the neighborhood (an industrial area tolerates more noise and odor than a residential one), whether the defendant's conduct violates a zoning ordinance or other regulation, the social utility of the defendant's activity, the practicality and cost of avoiding or reducing the harm, and whether the defendant's conduct came before or after the plaintiff's own use of the land began ('coming to the nuisance' is a relevant, though not always dispositive, factor).

The Restatement approach frames this as balancing the gravity of the harm against the utility of the conduct, though some jurisdictions instead ask only whether the harm was substantial and unreasonable to the ordinary person in the community, without a strict utility offset. The character of the surrounding area often does the most work in practice: identical conduct can be reasonable in one location and a nuisance in another.

Remedies include damages for the diminished use and enjoyment of the property (and diminution in property value for a permanent nuisance) and injunctive relief ordering the defendant to abate the interference, though courts weigh the relative hardship of an injunction on the defendant against the harm to the plaintiff before granting one, and sometimes award damages instead where an injunction would be grossly disproportionate.

Common defenses include compliance with applicable zoning or regulatory standards (relevant but rarely conclusive), the plaintiff's own hypersensitivity to a condition that would not bother an ordinary occupant, coming to the nuisance where the defendant's activity predates the plaintiff's occupancy and the area's character has not since changed, and, in some states, statutory 'right-to-farm' or similar protections for preexisting agricultural or industrial operations against newcomers.

In Juricratic, private nuisance is modeled around the reasonableness balancing test as its central decision node, rather than as a single pass/fail liability question. You set separate dials for the severity and duration of the interference, the character of the neighborhood, the social utility and cost-of-avoidance of the defendant's conduct, and any coming-to-the-nuisance or regulatory-compliance defense. Because the ultimate outcome is a balance rather than a bright-line rule, the simulation surfaces how sensitive the case is to a single fact — for example, a zoning change in the area, or evidence the defendant could cheaply mitigate the harm — and where the balance tips from a defensible operation into an actionable nuisance.