NYC Brownstone Fireplaces: Can You Use Yours?

What is usually behind the mantel

Brownstones and rowhouses in Brooklyn and Manhattan often have a fireplace on each floor, the best known on the parlor level behind a marble mantel. A lot of them were built for coal. Coal burns hot and compact, so the fireboxes were small and shallow, sometimes fitted with a cast iron insert or summer cover, and the flues were narrow.

Over the twentieth century, as central boilers took over, most were bricked up, covered with a board or left decorative. The flues were often sealed at the top, at the bottom, or not at all. A house can have six or eight fireplaces and only a handful of them still connect to an open flue.

How the stack is built

The flues in a brownstone usually rise inside a party wall or a chimney mass shared with the house next door. Each fireplace has its own flue, separated from its neighbors by a thin brick partition called a wythe. Some flues were lined with clay tile; many older ones are bare brick with a coat of parging inside.

That layout explains most of the problems we find. A crack in a partition can let smoke from one flue into another, or into the neighbor's house. Water entering at the top travels down several flues at once. And the boiler flue for one house may run right beside a fireplace flue for the other.

Signs a fireplace may be workable

Some fireplaces are much closer to usable than others, and a few observations from inside and from the street help sort them before anyone opens a wall.

• An open firebox rather than one bricked up flush with the wall
• A damper, or at least a clear throat you can see up through with a flashlight
• No soot stains or blistered paint on the wall above the mantel
• Flue tops on the roof that are open or capped, not mortared shut
• No signs of water: rust, stains on the chimney breast, crumbling plaster

What the inspection looks at

Each flue gets checked on its own, from the firebox to the top, because condition varies flue by flue in the same stack. The technician looks for missing or broken tiles, gaps in the partitions, debris shelves where bricks have fallen, and any sign the flue was later connected to a boiler or water heater. The firebox depth and opening size are measured, since they decide whether wood can burn without smoking into the room.

On the roof, the crown, the flue tops and the flashing against the neighboring roof are checked. A brownstone chimney often sits right on the property line, so the inspection notes which parts are shared and which belong to each house.

Expect the visit to take longer than a single-flue house. Several fireplaces may need to be opened, and smoke or a light dropped down one flue at a time shows which opening belongs to which flue on the roof. That map is worth keeping: it saves time on every future repair.

What restoring one usually involves

Old coal fireboxes are often too small and too shallow for logs. Some can be rebuilt deeper with firebrick; others suit a gas insert sized for small openings. Most of these flues need a liner: either they never had one or the clay tiles are cracked. A stainless steel liner sized to the fireplace opening, or a cast-in-place liner where the flue is irregular, is the usual fix.

The work also covers a damper, often top-sealing, a cap, and a hearth extension in front of the opening if the original one is short. Where the partition between flues has failed, relining also restores separation between them, which matters in a shared stack.

• A shallow coal firebox spills wood smoke into the room; it is rebuilt deeper or fitted with a small gas insert
• An unlined or cracked flue lets heat and smoke reach the brick and the neighbors; a stainless or cast-in-place liner fixes it
• A missing damper means heat loss and drafts all winter; a top-sealing damper at the flue outlet solves it
• A flue sealed at the top cannot vent at all; it is opened, inspected and capped
• Water at the chimney breast means the crown, cap or flashing is failing and needs repair

Wood, gas or electric in a brownstone

The choice usually comes down to the firebox size, the flue and the rules that apply to the building. A deep enough firebox with its own lined flue can burn wood where the fuel rules allow it. A shallow coal opening is often a better match for a small gas insert, which vents through its own liner and needs a gas line run by a licensed plumber. Where no flue can be made usable, an electric unit gives a flame effect with no venting at all.

Owners often decide room by room. A parlor fireplace might be restored for occasional fires while the bedroom fireplaces upstairs are sealed and capped, or fitted with electric units. Planning the whole stack at once is cheaper than returning to the roof for each flue separately.

City rules worth checking

New York City's Mechanical Code says solid fuel fireplaces must be installed, altered and maintained in line with the city's Air Pollution Control Code, and allows new ones only if they burn fuel types that code allows. Read the current Air Code or ask the city before you plan a wood fire, and if the house is a co-op or condo, check the building's rules as well.

If the house is a designated landmark or sits in a historic district, the Landmarks Preservation Commission says its approval is needed for work that affects the exterior appearance, such as changes to the chimney or a new cap visible from the street. Confirm with the Commission before exterior work is scheduled.

Caring for the marble mantel

Marble mantels are soft and etch with acids. Skip vinegar and harsh cleaners; a damp cloth and a stone-safe cleaner handle ordinary dirt. A mantel that has pulled away from the wall should be secured before anyone leans a ladder on it or hangs heavy decorations. If the fireplace will burn again, keep the clearances it needs between the opening and any wood trim, and keep fireplace tools from chipping the slab hearth.

Cast iron summer covers and coal grates are worth keeping even if the fireplace is converted. They are part of the house's character, and a restorer can often refit them in front of a gas insert or a sealed opening.