Why River Wards chimneys are their own animal
Most chimney advice assumes a freestanding house with a single masonry stack and a wood-burning fireplace. Very little of the River Wards looks like that. The older blocks are wall-to-wall rowhomes, two and three stories, built tight against their neighbors with shared party walls and chimney stacks that often carry more than one flue. Those flues were cut for coal heat and a parlor fireplace, then pressed into service for an oil burner, and finally tied to a gas boiler or water heater somewhere along the way. Each step left a flue that no longer matches the appliance below it, which is exactly the condition that breeds backdrafting, condensation, and slow liner failure.
Layered on top of that is a wave of new-construction infill, heaviest in Fishtown and Northern Liberties, where vacant lots and torn-down warehouses have become modern homes. These newer houses are airtight and well insulated, and many vent their heat through a framed chimney chase rather than a brick stack, with a metal liner or a direct-vent appliance. That tightness creates its own draft problems, because a sealed house can starve a flue of the makeup air it needs to draw. A crew that only knows old brick chimneys will miss what is happening on a new infill build, and a crew that only knows new construction will misread a hundred-year-old coal flue. The River Wards need both kinds of knowledge on the same truck.