But before they do, your chimney might just spring a leak.  After all, a chimney is just a big sponge. Like a sponge — when it gets saturated, the water will run out anywhere and anyhow it can. Depending on how many bricks are exposed to the elements and available to soak up water, there is the potential for a great deal of water, to be managed, and with it the possibility of leaking into your home’s structure.  If it is not dealt with, over time, the chimney structure can even become compromised.

If you’d like to know more about water’s effects on masonry chimneys, please feel free to check out CSIA.ORG.

Sometimes it is obvious where the water is coming in. Given enough time, it will make its presence known.  However, more insidious water leaks often go unnoticed until there is damage and can be difficult to diagnose as to the exact entry point. Usually, there is more than one problem. A visual inspection can reveal likely possibilities and probable remedies. Sometimes where the water is being seen can indicate one or more of the four most common sources as being the most likely point of entry. In other cases, it is a trial and error process to pinpoint the source.

Most Common Points of Entry

  • No chimney cap or too small chimney cap
  • Cracked and porous crown wash
  • Absorption through brick due to
    • Old, porous brick and/or mortar
    • Deteriorated mortar joints with voids/holes
  • Deteriorated or badly installed flashing
  • No cricket or saddle on the broad side of a chimney downhill from a peak

There are products and methods to address these problems.

  • A full coverage chimney cap, preferably with a lid (with drip edge) that overhangs the sides of the chimney, can prevent rain from entering the flue and provide added protection for crown wash.**
  • An elastomeric coating can seal the crown wash or a cast and poured crown with a drip edge can be created. Either option helps prevent water from freely soaking in from the top.
  • A breathable water repellant and/or crack sealer designed for chimneys applied to the brick and mortar can prevent water from soaking in from the sides.
  • Deteriorated mortar joints can be tuck-pointed.  Holed can be filled.
  • Complete rebuild may be necessary if an aging chimney is too deteriorated to repair.
  • Metal flashing can be repaired or replaced; or a flexible, surface bonded flashing can be applied to correct improper or deteriorated flashing.
  • A cricket can be added to the roof at the base of a chimney where water tends to puddle during heavy rains.

How do you know if it’s the chimney or the roof?

One way is to wrap the chimney with plastic and wait for rain.   No sign of water even though it rains, says it’s probably the chimney.   If you still see water with the rains when the chimney is wrapped, the leak is probably in the roof uphill from the chimney and water is running down to the chimney.

**More information from Blue Sky Chimney Sweeps|Bless Your Hearth about chimney caps can be seen on this website at  Chimney Caps & Animal Guards  or  Two-for-One