Chimneys

Published on December 26th, 2015 | by Henri

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Leaks through ceiling next to chimney

Q.  Our house was built 105 years ago. We have had this leak in the master bedroom ceiling for over 6 years and we have spent over $20,000 on repairs.

The leak is on all 3 sides of the fireplace at the ceiling. Above the ceiling is a chimney which is made of large marble blocks. We have had all the slate removed from the gutter to the apex of the roof. The area of slate removal extended three feet past both sides of the chimney.  A new ice-and-snow barrier was put down before the slates were reinstalled along with replacement of any damaged slates. We also had the copper cricket replaced and made larger along with new, higher flashing.

The chimney has a copper cap which was re-cemented. We cannot close off the chimney because the heating system uses one of the flues. Despite all this the leak persists. We have now been advised to direct our efforts toward re-pointing the chimney and coating it with a sealer. This will be another $10,000 which, out of desperation, we are willing to spend if there is a significant chance it will help.

Needless to say we are at our wits end. Can you please offer advice and suggestions? We will appreciate anything you can do to finally get this problem solved.

A.    Was the ice and water membrane brought up the sides of the chimney by a few inches, and covered with the new flashing? This would ensure that water that might get under the flashing, if the flashing was just caulked instead of being inserted in the marble blocks’ joints, would not penetrate into the ceiling below.

But if the flashing at the base of the chimney was done correctly when the repairs were made, it sounds as if the problem is with the marble blocks. Have them repointed and have the entire chimney sealed with a clear sealer. Be sure that the product you use is siloxane-based. It will allow the marble blocks to breathe and dry up but seal out the penetration of water.

But you might want to investigate other possibilities before embarking on this large expense.

Is the copper cap over the chimney installed on the masonry with holes for the flues or is it raised on legs? If just covering the masonry, there might be small openings or spaces through which rain may enter. If this is the case, consider having a cap set on legs, leaving a minimum of six inches clear for the heating system’s gases to escape. If one or more flues are venting a wood-burning fireplace or stove, the clearance should closer to eight or 10 inches.

If the other flues are unused, they could be closed off with slates set in an adhesive, such as plastic roofing cement, as extra precaution.
If you are planning on updating your heating appliance, it should be vented through a band joist and not into a chimney, in which case the entire chimney top can be sealed off.

I am surprised at the enormous cost you have paid so far and at the price you have been quoted for pointing and sealing the chimney; have you received several estimates? You should.

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