Chimneys on Old Capes and Federal Houses Around New Bedford

The house types and their chimneys

The Massachusetts Historical Commission’s town surveys describe the area’s early houses in detail. In Acushnet, the Sprague House of 1720 is a gambrel-roofed center-chimney cottage, and center-chimney Capes predominate among later cottages, especially on outlying roads. In Dartmouth, a center-chimney cottage and house at Russells Mills both date to 1723. Fairhaven’s Federal center has houses with interior chimneys on raised basements, and a regionally distinctive three-story end-chimney Federal house.

New Bedford itself is unusual. Its survey notes that the city never widely built the center-chimney Cape; instead three-bay and four-bay houses with interior chimneys went up close together on a grid, followed by brick Greek Revival houses with linked parapet end chimneys in the whaling era.

What makes old chimneys different

• Lime mortar: softer and more breathable than modern mortar, and meant to wear before the brick does.
• No liners: most flues of this age were built without clay tile liners, so the inside is bare brick and mortar.
• Several flues in one stack: a center chimney typically served fireplaces in several rooms.
• Shallow fireboxes: some fireplaces were built or rebuilt for coal and are shallower than wood-burning ones.
• Alterations: over two centuries, flues get closed, reused for heating appliances, or patched with whatever mortar was at hand.

Repairs that help, and repairs that harm

The most common mistake on an old chimney is repointing it with a hard, cement-rich mortar. It makes the joints stronger and less breathable than the brick around them, so moisture escapes through the brick instead and the faces spall. Good repointing uses a mortar matched to the existing masonry and rakes out failed joints to proper depth.

Film-forming sealers and paint cause similar trouble by trapping moisture. If the brick needs protection, the right choice is a breathable water repellent made for historic masonry, applied only after the joints, crown and flashing are sound. Sometimes the right answer is to leave the brick untreated.

Using an old fireplace again

An old fireplace that has sat unused, or that was closed up decades ago, shouldn’t be lit until it has been inspected. Unlined flues, cracked or missing mortar inside the flue, shallow fireboxes and wooden framing too close to the chimney are all common in houses of this age.

A Level 2 inspection, with a camera through each flue and a look at the chimney where it passes through the attic and basement, shows what each flue is fit for. Depending on what it finds, a flue may be fine as is, need repointing inside, or need a liner before regular use.

Heating appliances in historic stacks

Many old center chimneys now carry a flue for an oil or gas boiler alongside the fireplace flues. An unlined masonry flue is generally a poor match for a modern appliance: its exhaust can condense, and the acids attack soft old mortar. When the heating system is replaced, the appliance’s venting instructions and the code decide what the flue needs, often a liner sized for the new appliance.

Fire safety in very old chimneys

Colonial and Federal builders didn’t work to modern clearances. Floor joists and framing were often built tight against the chimney, and over two centuries wood dries, mortar falls out of joints and gaps open between flues. In an unlined flue, a hot fire or a chimney fire can find those gaps. That is one reason an old flue that will be used regularly is often relined, which restores a continuous, sealed path for smoke and heat.

The inspection also looks at the attic and basement, where the chimney passes through framing, for charring, heat damage or signs of past fires. Those areas are rarely seen otherwise and are where hidden problems tend to be.

Keeping the look while doing the work

Owners of old houses often worry that chimney work will change how the house looks. Most of it needn’t. Repointing can match the color and joint profile of the old mortar. A stainless liner is invisible from outside once its top plate and cap are fitted. Where the top of a chimney has to be rebuilt, sound old brick can usually be cleaned and reused, and decorative details rebuilt. Where something visible must change, the options can be discussed before any work starts, and the local historic commission consulted if it applies.

A sensible order of work

1. Inspect first, including a camera through each flue, before deciding anything.
2. Stop water at the top: crown, cap and flashing, because everything else depends on it.
3. Repoint failed joints with a matched mortar, outside and, where needed, inside the flue.
4. Reline any flue that will serve a stove, insert or heating appliance, sized to that appliance.
5. Only then consider a breathable water repellent for exposed, porous brick.

Working in that order avoids paying for interior or cosmetic work that water from a failed crown would undo within a few winters.

Historic rules

Sources we checked

• Massachusetts Historical Commission: Reconnaissance Survey Town Report, Acushnet
• Massachusetts Historical Commission: Reconnaissance Survey Town Report, Dartmouth
• Massachusetts Historical Commission: Reconnaissance Survey Town Report, Fairhaven
• Massachusetts Historical Commission: Reconnaissance Survey Town Report, New Bedford
• NFPA 211: Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances

General information for homeowners from Chimney Champ’s New Bedford. It cannot stand in for an inspection of your own chimney, and questions about code are decided by your local building or fire official.