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How to Assess and Repair a Leaking Chimney

May 21, 2019Chimney

Well, it’s springtime once again and the storms are coming through every couple of days. Most of the time we are thankful for the rain and happy to see our lawns and gardens come back to life, but if you have a leaking chimney it can create a sense of foreboding that will ruin the joys of spring. In this article we are going to discuss the types of leaks most commonly found in fireplaces and chimneys, and how to diagnose and repair them properly.

The most important part to fixing a leak is to find the leak. The source of the leak can be difficult to find, and is often originating nowhere near where the water is collecting. So, in order to help you identify a starting point, we will list the most common types of leaks we have found in our 30+ years of repairing chimneys.

  1. Water is dripping down into the inside of the fireplace.
    • This is generally caused by rain getting blown into the flue at the top of your chimney, or the lack of a proper fitting chimney cap. In heavy rains accompanied by wind, even a properly capped chimney will leak. This can sometime be mitigated by the installation of a top mount sealing damper depending on the type of fireplace/chimney you have.
  2. Sheetrock damage to the ceiling or walls above the fireplace.
    • These leaks can prove to be the most difficult to diagnose as they can originate from so many different areas. The most common places of origination are the chimney exterior, mortar crown, the chimney/roof flashing, portions of the roof that are “uphill” from the chimney, and faulty chimney caps/siding & brick.
  3. On the floor around the fireplace.
    • Typically, these leaks are caused by only one of two things; either a missing mortar crown (masonry fireplace), or a failing/improperly installed bottom pan or storm collar (manufactured fireplace).
  4. In the attic above the fireplace.
    • This type of leak is almost always due to a failing roof flashing, damaged siding/brick, or a missing/damaged chimney cap.

Now that we have identified the 4 most likely types/causes of chimney leaks, we can really simplify the pin pointing of your leak. Don’t over think this, and it will be easy to fix your leak.

  1. If you have a manufactured/factory built fireplace and chimney, you will first want to identify the material used on the exterior of the chimney (i.e. siding, brick, stone, etc…)
    • IMPORTANT! A chimney that has pipe for a flue and a chase “chimney” built around it will always leak if it has brick or stone used as a veneer. A chimney built like this should ALWAYS be sided. Masonry absorbs water and passes it into the attic. Brick or stone used on a chase will always leak and should be removed and replaced with siding to stop the leak.
  2. Missing chimney cap. If you don’t have one, you need to install one before moving forward with any repairs.
  3. Water leak test. This will generally require at least 2 people and a water hose. The idea here is to saturate the chimney and roof in sections to identify the area that the leak is originating from. See the illustration:

leaking chimney

First, you will need to get at least 1 person into the attic or interior space near the chimney. This person needs a light and a way to mark the area leaking once it is found. Second, someone will need to be on the roof with a water hose fitted with nozzle that can be turned off without going back down a ladder. Third, make sure you leave a path on/off the roof that will avoid the wet areas, and make sure the person is tied off on the roof.

Starting in the area noted zone #1. This is the area from the roof peak or the highest point on the roof above the chimney. Begin saturating the roof with the water hose while making sure NOT to spray the chimney itself. Generally, you will need to run water for 10-15 min before a leak is exposed. If the person in the attic begins seeing water leak in, they will need to mark it before moving on.

Next you will move down the roof to the area marked zone #2. This is the area of the roof approx. three feet above the flashing, and the area on the chimney approx. one foot above the flashing. Saturate this area heavily. Working slowly from left to right. If the chimney has brick or stone on it’s exterior you want to wet it until the masonry is saturated. Again, give it 10-15 minutes of heavy watering before moving on. Mark any leaks in the attic or ceiling before moving on.

At this point you may want to take a break and let the roof dry before moving on.

Zone #3 is the area of the chimney that is one foot above the flashing to one foot below the chimney top. Try to saturate one side at a time as you work around the chimney. These leaks can be difficult to mark in the attic as it is usually a tight space. Using a bright spray paint or landscaping flags can add a little extra reach for the person marking the leak. Apply water for 15-25 minutes here as it can take a while to locate the leak in the attic.

Finally, we will move to zone #4. You will want to try and use your water hose to create “rain”-like saturation. Spray water up so it falls like rain down onto the chimney top. Because you are not spraying the chimney directly it may take a little longer to saturate this portion.

Okay, I’ve found my leak so who do I call?

Zone #1: Always call a roofer. This area is above the chimney and in no way connected to it.

Zone #2: Leaks in this area are usually flashing related. Flashing is part of the roofing system and not the chimney. Call a roofer first. If the roofer says the flashing is fine then contact a chimney professional.

Zone #3: Leaks here are always due the following:

      1. Missing bricks or mortar. Call chimney professional or mason
      2. Damaged siding. Call siding repair or paint company.
      3. Improper construction. If the chimney has a pipe inside and a brick or stone exterior, you will need to have siding installed. You should start with a chimney professional for verification, but usually you will need a mason or siding company to properly fix this leak.

Zone #4 Any leaks in this area should be first addressed by a chimney professional. Depending on the cause of the leak; your chimney professional may repair it themselves, or refer you to a qualified tradesman.

In conclusion; water leaks suck. They are time consuming and often costly to repair. However, if you follow these guidelines you will certainly find your problem. Be patient with any interior repairs until you have had a few good storms to prove your repair has worked. Good luck and stay dry!

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