The law of 'nuisance' is often classed as falling within the field of tort law; however, some legal academics view nuisance as independent of tort law. Regardless, nuisance is viewed as very broad and historical.
Defining nuisance law, and the confines of what constitutes nuisance, is often very challenging. Doing so is even challenging for the judiciary. Recently, within the case of Desando v. Canadian Transit Company, 2018 ONSC 1859, the following was stated:
 In the Law of Torts in Canada, 3d ed (Toronto: Carswell, 2010) by Gerald H.L. Fridman, Professor Fridman outlines the challenges courts are presented when “[t]he impossibility of providing a definition of nuisance for legal purposes has frequently been stated. Nuisance is a vague doctrine, very difficult to define accurately.”
 In Canadian Tort Law: Cases, Notes and Materials, 14th ed (Markham: LexisNexis Canada, 2014) by The Hon. Allen M. Linden, Lewis N. Klar, and Bruce Feldthusen, the authors open with an encapsulation:
Nuisance is a field of liability that describes a type of harm suffered by the plaintiff, rather than a type of objectionable conduct engaged in by the defendant. Public nuisance deals with the use and enjoyment of the general public’s right to use and enjoy public areas such as rights of way. A private nuisance is a substantial interference with an occupier’s use and enjoyment of land, an interference which is unreasonable in the circumstances. The “substantial” requirement eliminates consideration of trivial interferences. The “unreasonable” requirement is determined by a balancing exercise that considers factors such as the severity of the interference, the duration, the character of the neighbourhood, the sensitivity of the plaintiff and the utility of the defendant’s conduct. . . . In the absence of physical damage, the so-called loss of amenity cases, the balancing exercise may be detailed and difficult.
The essential aspects of nuisance appear as conduct or activity that constitutes as a substantial and unreasonable interference in the use and enjoyment of neighbouring lands. In respect of what is 'reasonable', the Supreme Court of Canada in Antrim Truck Centre Ltd. v. Ontario (Transportation),  1 S.C.R. 594 stated:
 The nature of the defendant’s conduct is not, however, an irrelevant consideration. Where the conduct is either malicious or careless, that will be a significant factor in the reasonableness analysis: see, e.g., Linden and Feldthusen, at pp. 590-91; Fleming, at s. 21.110; Murphy and Witting, at p. 439. Moreover, where the defendant can establish that his or her conduct was reasonable, that can be a relevant consideration, particularly in cases where a claim is brought against a public authority. A finding of reasonable conduct will not, however, necessarily preclude a finding of liability. The editors of Fleming’s The Law of Torts put this point well at s. 21.120:
. . . unreasonableness in nuisance relates primarily to the character and extent of the harm caused rather than that threatened. . . . [T]he “duty” not to expose one’s neighbours to a nuisance is not necessarily discharged by exercising reasonable care or even all possible care. In that sense, therefore, liability is strict. At the same time, evidence that the defendant has taken all possible precaution to avoid harm is not immaterial, because it has a bearing on whether he subjected the plaintiff to an unreasonable interference, and is decisive in those cases where the offensive activity is carried on under statutory authority. . . . [I]n nuisance it is up to the defendant to exculpate himself, once a prima facie infringement has been established, for example, by proving that his own use was “natural” and not unreasonable.
Whereas nuisance law can be broadly interpreted, the possibilities for application of nuisance law enables significant creativity. Cases are known to involve industry emanated pollutants; Smith v. Inco Limited, 2011 ONCA 628, noise or music; Gordner v. 2384898 Ontario Limited, 2017 CanLII 9631, harassing by telephone; Motherwell v. Motherwell, 1976 ALTASCAD 155, roadway salting operations; Schenk v. Ontario,  2 S.C.R. 289, altered water runoff; Hammer v. Kirkpatrick, 2017 ONSC 7150, grazing horses; Northern Light Arabians v. Sapergia, 2011 SKPC 151, unnatural soil excavation resulting in structural support loss; Desjardin v. Blick, 2009 CanLII 13026, harassment by neighbours; Johnson v. Cline, 2017 ONSC 3916, roots or branches of trees; Yates v. Fedirchuk, 2011 ONSC 5549 (roots); Freedman v. Cooper, 2015 ONSC 1373 (branches), among other things.
Harassment by Neighbours
Nuisance matters appearing unfortunately common are 'harassment by neighbours' cases. Frequent among these cases, it appears that an initial incident develops into a campaign of strife in retaliation for initial incident. As said in Lipiec v. Borsa,  O.J. No. 3819:
1 This is a tragic case, not because it is of any legal significance and not because it involves serious injury or damage to a party, it is tragic because for the past five years, the parties, who are adjoining homeowners at 27 and 29 Park View Gardens, Toronto, have been involved in a vicious, mean-spirited feud.
2 The issues in this lawsuit have consumed much of their time, energy, and of the joy which should be present in their lives, along with a great deal of their financial resources.
As for acceptance of nuisance law for application in matters involving harassment by neighbours there is an extensive body of cases covering the issue. Appearing strongly supportive is the case of Rathmann v. Rudka, 2001 CarswellOnt 1206 where it was said at paragraph 20:
… the case authorities cited by counsel for the plaintiffs show that the courts are giving monetary awards to persons subjected to neighbourly misconduct and who are affected by it. Much depends on the facts, but it does appear that if the court finds misconduct which causes even mild distress, then the court is prepared to grant an award of damages to compensate the aggrieved party. And perhaps this is the way it should be. … what can a person do when subjected to neighbourly misconduct be it, for example, regular loud playing of music … conduct which interferes with other persons right to privacy and their quiet use and enjoyment of their property. There is no recourse unless the courts are prepared to receive these complaints, and if necessary, extend the law of private nuisance to cover the realities of the present age, and attempt to assess damages as a deterrent. Should misconduct and the damaging effect thereof be proven, then a further deterrent might well be an award of costs on a solicitor and client basis. Such an award would act as both an encouragement and a deterrent to bringing frivolous actions.
Similarly, per Saelman v. Hill, 2004 CanLII 9176, offensive conduct which may consist of separately recognized or otherwise labelled wrongdoings manifest as nuisance whereas it was stated:
 I am of the view that the tort of nuisance is made out in circumstances where a neighbour deliberately, significantly and unjustifiably interferes with another neighbour’s enjoyment of his or her property. This type of conduct may be labelled as harassment, intimidation or invasion of privacy and in my view, are in essence manifestations of the well-established tort of nuisance.
Also of interest as per the Saelman case, it appears that in addition to owners of lands, the occupiers without a proprietary interest in the land but who are rightfully in possession of lands may bring action in the tort of nuisance whereas it was said:
[38 ] It has been suggested in many of the older cases that for a plaintiff to succeed in nuisance, a proprietary interest in the subject property must be established. This would exclude the plaintiff Mr. Wuerch who resides with Mr. Saelman, as his partner, but without any ownership in the property. With due regard to the historical background to the tort of nuisance, the lawful occupation of a residential property should, as a matter of policy, be protected by the law of nuisance irrespective of whether a claimant can establish a proprietary interest.
Furthermore, and also per Saelman, it appears that a series of incidents may be actionable despite the triviality or minor concern involving the incidents if each incident were viewed individually:
[41 ] In summary, I find that the actions of the defendants, particularly Mrs. Hill, in the summer of 1999 through to the time when an injunction was granted by Belch J. on January 25, 2001 on agreed upon terms, constituted a campaign of harassment amounting to an actionable nuisance. Most of the incidents were minor and not individually actionable. However, taken collectively, the defendants’ continued digging along the fence line, their channeling of water in order to destabilize the fence and distress the plaintiffs, the surveillance camera, floodlight, and no trespassing signs, the eavestroughing downspout directed onto the plaintiffs’ driveway, the personal confrontations and threatening behavior initiated by Mrs. Hill, all contributed to a loss of enjoyment of plaintiffs’ property. I find that an actionable nuisance has been established based on this unjustified harassment which the plaintiffs have been forced to endure.
The cost to remedy or mitigate nuisances appear as commonly awarded. In Yates, the cost to install barriers was suggested as a reasonable remedy for the nuisance caused by intruding tree roots.
In the 'harassment by neighbours' cases, costs to secure peace were compensable including the expense of surveillance camera equipment; Rathmann, as well as the expense to install fencing; Saelman.
Per Saelman at paragraph 44 and Johnson at paragraph 124, awards were assessed separately; firstly as a sum intended to compensate for 'interference with residence' as well as a sum for mental distress. Furthermore, whereas the 'harassment by neighbours' causes reasonably expected distress, general damages are available without medical expert evidence or a need to of establishing a psychiatric condition; Johnson at paragraph 123, Rathmann at paragraph 35. In Fitzpatrick at paragraph 154, it was particularly noted that damages for nuisance by harassment that interferes with enjoyment of residence, whereas, "... home is supposed to inspire feelings of comfort and safety, not fear and intrepidation ...", deserve a premium. Where harassing conduct was particularly oppressive, spiteful, malicious, and prolonged, damages of $10,000 was awarded; Garrett v. Mikalachki, 2000 CarswellOnt 1298 at paragraph 152.
Even in cases involving unintentional nuisance, such as the nuisance via grazing horses in Northern Light Arabians, general damages were required to encourage preventative efforts.
Per Fitzpatrick v. Orwin, 2012 ONSC 3492 at paragraph 171, a 'harassment by neighbours' case, which involved intentional conduct deemed reprehensible intimidation that went as far as the placing of a dead coyote upon a vehicle and the issuance of threats and insults, punitive damages were awarded.