Water is coming through the ceiling. The board says it's your problem.

NY RPL § 235-b

The standard split: building to the wall, you from the wall in.

Most New York co-ops use a proprietary lease descended from the same form, and the repair clause is remarkably consistent. The corporation is responsible for keeping the building in good repair, including the roof, exterior walls, foundations, structural elements, sidewalks, hallways, elevators, and the main and riser pipes, wiring, and conduits that serve more than one apartment. The shareholder is responsible for the interior of the apartment, including walls, floors, ceilings (as surfaces), fixtures, appliances, and the pipes and wiring that serve only that apartment, usually from the point where they branch off the riser.

That allocation answers most leak questions. Water entering through the roof, a facade crack, a window lintel, or a riser is the corporation's problem, full stop. Water from your own dishwasher hose or the trap under your sink is yours. Water from the apartment above is a three-way question: the upstairs shareholder is responsible if the source is inside their unit, the corporation if it is a common pipe, and the damaged shareholder's recourse runs to whichever one it is.

The board's favorite move is to treat the damage as the issue rather than the source. Your ceiling plaster is "interior" and therefore yours, the argument goes. But the corporation's failure to maintain the roof caused the damage, and a party that breaches its repair obligation is liable for the resulting harm. The lease may even say so expressly. Read your lease's repair paragraph and the paragraph on damage from the corporation's negligence; together they usually settle it.

What the warranty of habitability adds.

Separate from the lease, Real Property Law § 235-b implies into every residential lease a warranty that the premises are fit for human habitation and free of conditions dangerous to life, health, or safety. New York's Court of Appeals has held that a cooperative corporation is a landlord for this purpose and owes the warranty to its shareholder-tenants. The warranty cannot be waived by the lease.

For leaks, that does two things. First, it makes the corporation responsible for fixing a habitability-level condition regardless of how the lease phrases the repair clause; a chronic leak, mold growth, or a ceiling at risk of collapse will qualify. Second, it gives you the remedy of abatement: a reduction of maintenance for the period the condition existed, proportioned to how much of the apartment was affected and how badly. A bedroom unusable for four months in a two-bedroom apartment might support an abatement on the order of a quarter to a third of maintenance for those months, depending on the facts. Courts have wide discretion, and the numbers vary, but the principle is settled.

The warranty is a co-op tool. Condo unit owners are not tenants and cannot use § 235-b; their claims rest on the bylaws' common-element repair obligation and ordinary negligence. Our hub on co-op and condo boards that won't act covers the distinction.

Insurance, and why the board keeps mentioning it.

Boards often respond to a leak by telling the shareholder to "put it through your insurance." Sometimes that is the right practical path: your policy pays for your damaged property and then pursues the corporation. But it does not change who is responsible. A corporation that has breached its repair obligation is liable for the damage whether or not you carry insurance, and an uninsured shareholder is not out of luck. What insurance does change is strategy. If you have coverage, file the claim and also send the demand; the carrier's subrogation claim and your own demand push in the same direction.

Documenting a leak so the claim holds.

Leak cases are won on the record, and the record is built while the water is still coming in.

• Photograph and video everything, dated. Active water, staining, bubbling, mold, damaged contents. Repeat each time it recurs.
• Report in writing every time. Email the managing agent, not just the super. A leak log with dates of each report and each response is the single most useful exhibit.
• Get the source identified. Ask in writing what the cause was found to be. If the building's plumber or roofer wrote a report, request it.
• Keep the repair paperwork. Every patch, every paint job, every "we resolved it" email that preceded the next leak.
• Get an estimate. A contractor's written estimate for the interior restoration sets the damages number.
• Note the impact. Rooms you could not use, nights with buckets, a child moved out of a bedroom. This drives the abatement.

A worked example.

A shareholder on the top floor of a Bronx co-op reports a leak over the bedroom in October. The handyman patches and paints. It returns in December and again in February, each time reported by email. In March a roofer finally finds a failed flashing and repairs it. By then the ceiling has been opened twice, the closet contents are ruined, and the bedroom has been unusable for most of five months. Maintenance is $1,400 a month. A contractor quotes $4,800 to restore the ceiling and closet.

The claim against the corporation: $4,800 in restoration, the replacement value of the ruined contents (say $1,200), and an abatement for five months of a substantially impaired apartment, which at a third of maintenance is $2,333. Roughly $8,300, all of it traceable to a roof the lease made the corporation's responsibility, with five months of emails showing the board knew. That letter does not need to threaten much; it needs to be organized.

What a demand letter does here.

Our leak letters go to the board and the managing agent and do four things. They quote the lease's repair allocation and identify the source as a corporation-side element. They invoke § 235-b and describe the habitability impact with dates. They attach the leak log, photographs, and the estimate, and state the damages and abatement figure with the math shown. And they demand a permanent repair by a date, payment of the restoration and contents, and a maintenance credit for the abatement, with a short response window.

Letters like this usually produce one of three responses: a repair and a negotiated credit, a referral to the corporation's insurer, or a claim that the source is another shareholder's unit. The third is not a dead end; it narrows the dispute to a question the building's own plumber can answer, and our letter asks for that answer in writing. Where the board is slow but not hostile, the letter works as a catalyst rather than a threat.

A letter is not the right tool when the leak is from your own fixtures (then the corporation may have a claim against you), when the damage is trivial and the board has already fixed the source, or when the board is already in active litigation with you on the same issue. We will say so. How the service works: flat-fee demand letters.

If the board still will not act.

Co-op shareholders with a habitability claim can assert abatement defensively if the corporation sues for maintenance, but deliberately withholding invites a default notice, late fees, and legal-fee exposure under most leases; do it only with counsel. The affirmative routes are a damages action in civil court, small claims for amounts within the limit (see our New York small claims guide), and, for dangerous conditions in New York City, a complaint to HPD, which inspects co-ops as it does rental buildings. Related pages: sublet or alteration denied, books and records requests, and for renters, landlord won't make repairs.