Lambertville's median house dates to 1938, and 45 percent of its homes are attached houses, many of them in rows. On a row, each roof meets the next at a seam, and the seam is where a lot of leaks begin. Water that gets in there can show up on either side of the shared wall.
Raritan Township is newer, with a median house from 1986, but 22 percent of its homes are attached too. The same seam needs checking there, along with the flashing wherever a roof runs into a taller wall.
In the Highlands towns, from Lebanon Township to High Bridge, winter leaks often start at the eaves. Snow sits on the roof longer, melt water freezes at the cold edge, and the ice can push water back up under the shingles. The stain then turns up near an outside wall, a long way from the middle of the ceiling.
A ceiling stain tells you water got in. It does not tell you where. We go up, follow it back, and photograph the spot before we price the repair.