Chimney flashing on a new roof

Short answer: most leaks on older Hartford-area houses start where the roof meets a chimney, not in the open field of shingles. A replacement is when that joint is fully exposed, so it is the time to rebuild it properly.

The layers that keep a chimney dry

• Step flashing. L-shaped pieces woven in with each course of shingles up both sides of the chimney.
• Counter flashing. Metal set into a cut in the mortar and bent down over the step pieces.
• Apron. One piece across the downhill face, lying on the shingles.
• Cricket or back pan. On the uphill side, to send water around the chimney instead of letting it pool.
• Ice barrier. Self-adhering membrane turned up the chimney sides under the metal.

Why Connecticut chimneys leak

Freeze and thaw

Water in a mortar joint freezes and expands, again and again through the winter. Over years the joints soften and the counter flashing tucked into them works loose.

Patches on patches

Many chimneys have decades of tar smeared over the flashing. It traps water and hides the real problem.

Wide chimneys with no cricket

Large center chimneys on Colonials in Glastonbury and Wethersfield, and the big brick chimneys of Victorian houses in Hartford's West End, often have no cricket. Snow and leaves pile up behind them.

Unused chimneys

A chimney no longer used for heat may have lost its cap or crown and takes water in from the top.

Copper on older houses

Slate roofs on older Hartford, West Hartford and Wethersfield houses were usually flashed in copper. Copper outlasts most other metals, and on a slate roof that is being kept, it is often the flashing that is renewed rather than the stone. When a slate roof is replaced with asphalt, the flashing is replaced with it. See slate or asphalt for an older house.

Taking down an unused chimney

Some owners remove an unused chimney below the roofline during the replacement and deck over the opening. It removes the leak point for good, but it is structural work and the building department may need to be involved. See roof replacement permits.

Questions to ask before you sign

• Will all step and counter flashing be new?
• Will the counter flashing be cut into the mortar, or attached to the brick face?
• Does my chimney need a cricket?
• What happens if you find soft mortar or loose brick?

Before hiring, see how to check a Connecticut roofer.