Philadelphia is a rowhouse city on mostly flat streets. Brick runs in a line, party walls on both sides, a stoop at the sidewalk, and a roof that is often low-slope or flat behind a parapet. Summers are hot and humid. Winters are cold enough for ice and for a boiler that has to work. This is not a house on a hill. Water does not arrive from a slope above you. It arrives from the roof, the alley, the party wall, or the sky.
The block is the building. Stacks line up floor over floor. Window units hang over the sidewalk. Cornices and old brick take the weather. Some fronts wear a coating over the masonry. Rear yards are small, sometimes just an alley and a fence. Basements sit under the stoop and take rain when the street or the yard sends it there. Twins and larger houses exist, but the row is the ordinary job on this page.
Say the symptom in row language. A top-floor stain, a cold radiator, a mouse in the party wall, a bath that leaks into the kitchen below, a sash painted shut, a cellar that is wet after a hard rain, a question about your policy. Say which floor. Say whether you own the house or a unit, or you rent. If someone shares the wall and is also wet, say that. It changes the call.
Have the one fact that sorts the trade. Roof shape. Declarations page and deductible if this is coverage or a claim. What you saw, if it is a pest. Whether the boiler is out for the whole house. Narrow stairs and street access are the way work gets in. Mention them if a tub, a water heater, or debris has to move. Do not describe a driveway you do not have.
Keep the hill out of the story. Philadelphia is the row, the party wall, the stoop, and the roof that holds water. Pick the trade and call.