The same sequence on a small repair and a full replacement, so you know what comes next.
Describe what you are seeing. Most jobs are diagnosed from a short conversation and a photograph, before anyone travels.
A full walk of the roof and the attic space together, with every slope photographed before anything is moved.
A written quote against a written scope that names the detail that failed, so nothing is added later without your say-so.
The area is left clean, nails swept, and you get the before-and-after set for your records.
New York City requires a DCWP Home Improvement Contractor license for residential roofing. Ask for the number and check it on the DCWP register before work starts.
A like-for-like re-roof on a one- or two-family house generally does not need a DOB permit. Changing the structure, the pitch or the decking layout generally does.
Above a low threshold the work must be under a written contract setting out scope, price and payment schedule. That is the law, not a courtesy.
A New York contractor with employees must carry workers' comp, and on a roof it matters. Ask for the certificate rather than a verbal assurance.
Winter storms drive rain sideways and uphill, under laps that shed ordinary rain perfectly well. It is why a roof can be sound for years and then leak once.
Water in a crack expands when it freezes and opens the crack further. A hairline fault in October is a real one by March.
Escaping heat melts snow, the meltwater refreezes at the cold eave, and the ice pushes water back under the shingles. The cause is usually insulation and ventilation, not the covering.
Late-summer systems drop more rain in an hour than the gutters were sized for. Undersized runs overflow at the valleys and the water goes behind the fascia.
Tell us what you are seeing and roughly when it started.