What stays the same on both sides
New York State law does not care about the city boundary. Article 32 licenses mold assessors and remediators statewide, forbids any one company from taking on both jobs at the same address, and applies once the area passes ten square feet. A twelve-unit building in the Bronx and its twin in Mount Vernon fall under the same licensing rules for the same size of job, though who may do the work differs, as below.
What the city adds inside the Bronx
Local Law 55 of 2018 puts duties on owners of buildings with three or more units, among them: an annual inspection of every unit for indoor allergen hazards such as mold, a response to complaints from tenants or the city, and a vacant apartment that is clean and free of mold before the next tenant arrives. The city health department adds that in a building of any size, if a tenant has a diagnosis of moderate or severe persistent asthma, the owner must also keep that tenant's home free of mold, including repairing the leak behind it.
Administrative Code section 24-154, from Local Law 61 of 2018, goes further for covered buildings: those with ten or more dwelling units, or on a zoning lot holding 25,000 square feet or more of non-residential floor space. There, owners, managing agents and their staff may not carry out mold assessment, abatement or remediation covering more than ten square feet, and an Article 32 licensee has to. Before work starts, the remediator must give the city a notice with the work plan, at least two business days ahead, and the assessor then has seven days from completing the post-remediation assessment to file it. The New York City Housing Authority's own buildings are excluded.
The Department of Environmental Protection says penalties of $800 to $10,000 may apply if an owner skips the licensed assessor and remediator.
What changes in Yonkers, Mount Vernon, Pelham and New Rochelle
The Multiple Residence Law applies to all cities under 325,000 people and to towns and villages, so it applies in these four places. Past the line, the city's ten-unit bar in section 24-154 does not apply, so the state's section 933 exemptions govern who may do the work. Among them, an owner may work on their own home, and an owner of a building with more than four units may use its own employees, though not for mold work done for the public.
That is a legal permission, not advice. A building manager who is unsure what a plan should look like can still hire an independent assessor.
Who you deal with outside the city
Westchester County's list of local building department contacts shows Yonkers, Mount Vernon, New Rochelle and Pelham each with its own department, address and phone number. In Yonkers that is the Department of Housing and Buildings, and housing complaints go there. Mount Vernon's Department of Buildings enforces state and local codes and housing standards. Pelham's building department lists damage repairs, expressly including water damage, among the projects needing a permit application.
Westchester also has a law of its own: a landlord must hand every prospective tenant a Flood History Disclosure Form stating the flood zone and whether the property has flooded in the past ten years. If you are renting there, ask for it.
A practical note on licenses
On the state register on 6 October 2026, Pelham addresses showed two licensed remediators and no licensed assessors. That is only an address count, since licensed firms travel, but it means the assessor on a Pelham job is probably coming from elsewhere and the schedule should allow for it.
Which panel is yours?
The municipality your building stands in settles it, not the name on the mailing envelope. A building in the Bronx follows city rules even if its postal address sounds like Westchester, and a building in Mount Vernon does not.
Your next step
Tell us the full address and what you are looking at. We point you to the first rung that applies, whether that is an assessor, a drying firm or help reading a notice. See the places we cover and remember the $100 credit on your first booked job.
Send the full address and we point you to the first step that applies on your side of the line.