Chimney repair and rebuildsin Woburn, MA

How to read what your chimney is telling you, what each problem usually needs, and what sets the price, so you can go into an estimate knowing the right questions to ask.

Signs your chimney needs repair

• Crumbling or recessed mortar joints on the stack.
• White staining (efflorescence): salt left on the brick by water moving through the masonry.
• Spalling: brick faces flaking or popping off, often with pieces landing on the roof or in the gutter.
• A cracked or crumbling crown at the top.
• Loose bricks or a lean in the top courses.
• Water stains on the ceiling or wall beside the chimney, or dampness and a musty smell at the fireplace.
• Gaps or rust where the metal flashing meets the brick.

From the ground, binoculars or your phone's zoom will show most of this. You don't need to climb onto the roof to know it's time for a closer look.

Repoint, repair, rebuild or build new?

Repointing is the fix when the bricks are sound and only the joints have failed. The old mortar is raked out to a consistent depth and new mortar, matched to the brick, is packed in. Our brick repointing guide explains the method and why the mortar has to be softer than the brick.

Partial repair handles spalled or cracked bricks scattered through an otherwise sound stack. Those bricks are cut out and replaced one at a time with matching brick, and the joints around them are repointed.

A chimney rebuild is needed when the top of the stack is loose, leaning or so spalled that there isn't enough sound brick left to hold mortar. The chimney is taken down to solid brick, often at or just below the roofline, and rebuilt plumb with a new crown. A rebuild is also the time to check height. The residential building code used in Massachusetts, based on the International Residential Code, requires a masonry chimney to rise at least 3 feet above the point where it passes through the roof and at least 2 feet higher than any part of the building within 10 feet.

A new chimney is a build from the ground up. We build new masonry chimneys as well as repairing old ones, and the same height rules apply.

The crown: the chimney's roof

The crown is the slab across the top of the chimney around the flue. Many older chimneys only have a thin, flat wash of mortar there, which cracks within a few winters and lets water run down into the stack. A proper crown is thicker, slopes away from the flue, and overhangs the brick with a drip edge so water falls clear instead of running down the face. If the crown is cracked but the brick below is sound, replacing the crown can stop a leak that repointing alone wouldn't. A chimney cap is different: it's the screened cover over the flue opening that keeps out rain, animals and debris. It helps, but it doesn't do the crown's job.

Leaks at the roofline

Where the chimney passes through the roof, metal flashing seals the gap. On a brick chimney the upper piece, the counterflashing, is tucked into a mortar joint. When that joint fails, water runs behind the flashing and into the house, and it often looks like a roof leak. So a roofline leak can be partly a roofing problem and partly a masonry one. The flashing itself is metal and is often a roofer's job, while failed mortar and loose brick around it are masonry. A roofer or chimney sweep can tell you whether the flashing needs replacing. Water can also travel down inside the brick, so the stain on your ceiling isn't always right under the problem.

Chase covers versus crowns

A chase cover is the metal top on a framed chimney chase: the boxed-in, sided chimney common on newer homes with prefabricated fireplaces. Galvanized covers rust and can leak into the chase, which is why stainless steel replacements are popular. Chase covers are metal work, usually handled by a chimney sweep or roofer. A brick chimney has a masonry crown instead.

A note on fireboxes

Inside the fireplace, the firebox is lined with firebrick laid in refractory mortar, a heat-setting mortar made to take direct flame. Ordinary mortar breaks down under that heat, so open or crumbling firebox joints need refractory mortar, and the residential code calls for firebrick laid in medium-duty refractory mortar (ASTM C199). The heat-resistant "fire cement" or "furnace cement" sold in tubes is fine for sealing a stove pipe joint or a hairline gap. It isn't meant to rebuild firebox joints or reset loose firebrick. A chimney sweep or fireplace specialist is usually the right person to inspect a firebox and tell you what it needs.

Chimney safety and inspections

A chimney carries smoke and carbon monoxide out of the house. Cracked flue tiles or open mortar joints can let heat reach the wood framing around the chimney, or let exhaust leak where it shouldn't. The fire code standard for chimneys, NFPA 211, calls for chimneys, fireplaces and vents to be inspected once a year, and every home with a fireplace or fuel-burning appliance should have working carbon monoxide detectors on each floor and near sleeping areas. An annual sweep and inspection covers the flue. When it turns up failed mortar, loose brick or a stack that needs rebuilding, that's where a masonry contractor comes in.

How chimney repair is priced

We don't quote chimney work sight unseen or publish price ranges, because "chimney repair" can mean repointing a few joints, rebuilding the whole stack or building a new chimney. What sets the price: how many courses or how much area of brick is failing; whether it's a repair, a rebuild or a new build; the height of the chimney and the pitch of the roof, which decide the staging and safety setup; and whether matching brick has to be found. The look and the estimate are free.

Chimney repair around Woburn

From our Woburn office we repair chimneys in towns including Andover, Burlington, North Reading, Reading, Stoneham, Winchester and Woburn. Not sure we cover your town? Check our service area or just call. For other brick, stone and step work, see our masonry services.