Chimney Repair & Rebuilding: what to know
Connecticut has an enormous population of brick chimneys, many of them built in the 1800s and early 1900s, and almost all of them exposed to forty or fifty freeze-thaw cycles a year. A chimney is the most weather-beaten masonry on any building: sun on all four sides, no protection from driving rain, and a concrete crown on top that is only a few inches thick.
What usually needs doing
- Crown repair or replacement. The crown is the sloped cap on top of the stack. Once it cracks, water runs straight into the chase. A correct crown overhangs the brick with a drip edge and is separated from the flue by an expansion joint, most old crowns are neither.
- Repointing the top courses. The upper few feet take the worst of it. Cutting the eroded joints back to sound mortar and repacking them, with a mix matched to the original, is routine preventative work.
- Rebuilding above the roofline. When the top courses are loose, the brick faces have spalled, or the stack leans, the section above the roof comes down and goes back up.
- Flashing. Step flashing woven into the shingle courses plus counter-flashing let into a raked mortar joint. Not a smear of roof cement.
- Caps and dampers. A stainless cap over the flue keeps rain, birds and debris out of the liner.
What to ask for
Ask for photographs of the top of the stack: you cannot see the crown from the ground, and neither can anyone quoting from the driveway. Ask what mortar mix will be used on pre-1930s brick, because hard Portland-cement mortar on soft historic brick destroys the units. And if the fireplace or a heating appliance vents through the chimney, ask whether the flue liner has been inspected too; masonry repair and flue safety are related but separate questions.