The violation clock: HPD mold classes, deadlines and what happens at each step

How the class is decided

New York City classifies a mold violation inside a dwelling unit by the size of the affected area in a room. The class follows how much of a room is affected: class A covers under 10 square feet, class B covers 10 to 29 square feet, and class C covers 30 square feet or more and is the one HPD calls immediately hazardous.

The days you get

Class A allows 90 days to correct. Class B allows 30. Class C allows 21. Count from the dates printed on the notice itself. This guide describes how the system works and is not legal advice: a deadline on your notice runs on its own terms, whatever any website says.

What happens if the date passes

HPD moves an uncorrected class A violation up to class B, and an uncorrected class B up to class C; a false certification of correction has the same effect. A building that keeps open mold or leak violations in class B or C can be pulled into the Underlying Conditions Program, which can require the owner to commission a report from a registered architect or professional engineer on where the water comes from and to deal with the conditions within four months.

The scale of this in the Bronx is large. City inspectors recorded about 20,400 mold violations in the Bronx in 2024, the most of any borough, against about 13,600 in Brooklyn. Of the 104 buildings picked citywide for the 2025 Underlying Conditions round, 57 are in the Bronx.

Who may do the correction

For a mold project over ten square feet, Article 32 of the state labor law requires licensed workers, subject to its exemptions. Where a project falls under the city's Administrative Code section 24-154, the owner's certification of correction must carry affidavits from both the remediator and the assessor, along with proof that the plan and the assessor's final report went to the city's Department of Environmental Protection. Owners and managing agents of buildings with ten or more apartments, and their staff, cannot do mold work over ten square feet themselves.

Think about the source, not the stain

A correction that wipes the wall and leaves the leak invites the next inspector. Where the assessor can identify them, the plan names the underlying sources of moisture, and the repair of that source belongs in the same timetable as the cleanup.

If you are a tenant

Tell the owner first, in writing, keep dated photographs, and ask what the plan is. If nothing happens, you can complain to the city online or by phone at 311. In the Bronx, owners of buildings with three or more apartments have to respond to tenant and city complaints.

If your notice is not from HPD

In Yonkers, Mount Vernon, New Rochelle and Pelham, HPD has no say. A notice comes from the local building department, which handles permits, inspections and housing complaints on its own. Read the notice for the office that issued it and the date it names, and take it to that office with questions.

A sensible order of work

1. Read the class, the room and the date on the notice.
2. Put an independent assessor on the plan within the first days, not the last.
3. Have the source repaired alongside the cleanup, not afterwards.
4. Keep every report, affidavit and photograph in one folder.
5. Certify only once the assessor's clearance exists.

Your next step

Send us the notice details and the address. We connect owners and managers with the firms the correction needs, and show tenants what to ask their landlord for. Learn more on the mold violation help page. When you book your first job through us, $100 comes off it.