Chimney Flashing Repair in Hempstead, NY

Why does the chimney leak after a storm?

Because the flashing and the sealant at the base and the top take the wind and the rain, and a gap lets water run into the masonry or the attic. The water can run down the brick for a long way before it shows.

Water that gets under the step flashing runs along the roof decking and down the inside of the chimney wall. A gap at the counter flashing lets it run into the brick and out into the room below. The leak can be far from the chimney, which is why the attic check is important.

The top of the chimney is also exposed. A cracked crown or a failed cap lets rain run into the flue and the masonry, and the water can come out at the joints below. A repair at the base alone may not stop that.

Why do winter ice and thaw matter at the chimney?

Because the freeze and thaw cycle opens small gaps in the mortar and the sealant, and the water that gets in freezes and widens them.

Water that enters a gap in the winter freezes and expands, and it can crack the mortar and the crown. The thaw that follows lets the water run further into the masonry. Over several winters the damage builds up, and a chimney that looked sound can have a leak at the joints.

A thaw after a snowfall is a good time to check the chimney from the attic and the ceiling, since the water route shows clearly when the snow melts.

What is counter flashing and why does it matter?

It is the metal set into the brick joint above the step flashing, and it sheds water over the step flashing. A gap in the counter flashing lets water get behind the step.

Counter flashing is set into the mortar joint of the chimney, and the step flashing is tucked under it. Water runs down the chimney, over the counter flashing and onto the step flashing, which carries it down the roof. If the counter flashing has lifted or the joint has opened, water gets behind the step and runs into the roof.

A repair must renew the counter flashing and reseal the joint, or the step flashing will fail again. The roofer explains which parts need a mason, since repointing the joint is masonry work.

When does the chimney need a mason?

When the crown, the brick or the mortar joints are cracked or crumbling. The roofer notes the masonry work, and a mason should carry it out.

A roofer repairs the flashing, the sealant and the cap. Cracked brick, crumbling mortar and a damaged crown are masonry work, and they need a mason. The roofer records what was seen and recommends that a mason looks at the chimney, so the homeowner can arrange it.

A chimney that is not sound will keep leaking, however well the flashing is repaired. The note helps the homeowner decide whether the masonry work is needed now or can wait.

What should a homeowner check after a storm?

The base of the chimney from the ground, the ceiling beside it after rain and the chimney crown for cracks. Those checks catch the leak early.

From the ground, look at the base of the chimney for rust, gaps and bent metal at the flashing. Look at the top for cracks in the crown and loose mortar at the cap.

Inside, check the ceiling and walls beside the chimney for new stains after rain. A stain in that place is worth reporting straight away, since the water can run a long way before it shows.

• Look at the base of the chimney for gaps and rust
• Look at the crown and cap for cracks
• Check the ceiling beside the chimney after rain
• Report any stain with the date and place

How is the step flashing fitted, and what goes wrong with it?

Step flashing is a series of small pieces woven into the shingles along the slope beside the chimney. When a piece is missing or badly set, the water runs behind it and into the roof.

Each step of the flashing is laid with a shingle, so that the water flows over the top of each piece and down onto the next. The flashing runs up the slope beside the chimney and meets the counter flashing in the brick. If a step is missing, or a piece has been set out of line, the water runs behind it and soaks the decking beneath.

The roofer checks each step along the slope and renews any that have failed. The repair is then tested with water to confirm that the flow goes over the flashing and not behind it.