Unfortunately, I couldn't find a New Jersey case precisely on point. It appears that the landlord definitely has a duty to disclose a defect if it could be dangerous and causes injury.
Even in the absence of a covenant to repair, the law has long recognized, as an exception to the general common law tenet, that a landlord, knowing of an actually or deceptively concealed dangerous condition on the premises, is under a duty to disclose it to the tenant at or prior to the transfer of possession. Failure to do so, resulting in injury to the tenant or to a member of his family, gives a cause of action to the injured person. Faber v. Creswick, 156 A.2d 252, 31 N.J. 234 (N.J., 1959).
But what about non-dangerous defects that merely causes property damage? I couldn’t find a New Jersey case that discusses it. I found cases in other states that seemed to go both ways, so a broad search wasn’t much help. Another factor that may make a difference is that yours is a commercial lease rather than a residential lease (landlord’s usually owe a residential tenant greater duty in general). But again, who knows if that’s important in this case. I did find New Jersey case law that discusses duty in general:
Whether a duty exists is a matter of law, to be decided by the court, not the factfinder. Rogers v. Bree, 329 N.J.Super. 197, 201, 747 A.2d 299 (App.Div.2000). To determine the existence of a duty, a court considers fairness and public policy. Snyder v. American Ass'n of Blood Banks, 144 N.J. 269, 292, 676 A.2d 1036 (1996). Foreseeability of injury to others from a defendant's conduct is important, but not dispositive. Ibid. Whether a duty is owed turns on whether the imposition of the duty "satisfies an abiding sense of basic fairness under all of the circumstances in light of considerations of public policy." Hopkins v. Fox & Lazo Realtors, 132 N.J. 426, 439, 625 A.2d 1110 (1993). Such an inquiry involves "identifying, weighing, and balancing several factors — the relationship of the parties, the nature of the attendant risk, the opportunity and ability to exercise care, and the public interest in the proposed solution." Ibid.
Duty is not a rigid concept; it adjusts "to the changing social relations" of society. Wytupeck v. City of Camden, 25 N.J. 450, 462, 136 A.2d 887 (1957). To determine if a duty exists, we examine the totality of the circumstances. J.S. v. R.T.H., 155 N.J. 330, 339, 714 A.2d 924 (1998). "When the defendant's actions are `relatively easily corrected' and the harm sought to be prevented is `serious,' it is fair to impose a duty." Id. at 339-40, 714 A.2d 924 (quoting Kelly v. Gwinnell, 96 N.J. 538, 549-50, 476 A.2d 1219 (1984)).
Because the issue here is one of first impression, we look first to cases that imposed a duty to warn in similar, but not identical, contexts. In so doing, cases discussing the common-law obligations of a landowner to persons injured on the landowner's premises provide some guidance.
For example, in Monaco v. Hartz Mountain Corp., 178 N.J. 401, 840 A.2d 822 (2004), a traffic sign owned and installed on the defendant's property by the City of Newark became dislodged by a gust of wind and injured the plaintiff. Id. at 404-05, 840 A.2d 822. The Monaco Court concluded that even though the property owner did not own or install the stop sign, it had a duty to make reasonable inspections of its own property and the abutting sidewalk and take such steps as were necessary to correct or give warning of a hazardous condition located on the property. Id. at 418, 840 A.2d 822. Significantly, the Court noted that "a landlord may not sit idly by a hazardous condition affecting its property, regardless of control, when that condition places a third party in danger." Id. at 416, 840 A.2d 822 (our emphasis); see also Endre v. Arnold, 300 N.J.Super. 136, 142, 692 A.2d 97 (App.Div.1997) (same); cf. Tighe v. Peterson, 356 N.J.Super. 322, 325-26, 812 A.2d 423 (App.Div.) (social host has no duty to warn guest who has actual knowledge of dangerous condition that exists on property; duty limited to warning of condition of which guest is unaware), aff'd, 175 N.J. 240, 814 A.2d 1066 (2002); and compare Snyder v. I. Jay Realty Co., 30 N.J. 303, 316-17, 153 A.2d 1 (1959) (where dangerous condition exists that is known to a tenant, and the condition was not readily observable, tenant must either give warning or make condition reasonably safe). Siddons v. Cook, 887 A.2d 689, 382 N.J. Super. 1 (NJ, 2005).
I wish I could provide a more definite answer to your question. At this point, you can either see a local attorney who can spend more time on the issue than I could, or you can sue in small claims court and see what happens. Good luck, and if my posts have been helpful, please remember to accept. Thank you.