Five Main Reasons for Chimney Leaks – And How to Resolve Them

While there are multiple reasons why chimneys can leak, below are five main reasons that will account for the majority of the issues. We stress a chimney that is taking on a lot of water or moisture and not resolved in a reasonable time frame will likely lead to the acceleration of costlier internal chimney repairs in the future. Harky’s performs all repair work with Quality, Precision and Care and is backed by some of the longest warranties in the area.

#1 Simply Rain Going Straight Down From the Top

This one is obvious but very important. Chimneys without a chimney cap/rain cover will have a massive amount of rain falling straight down into it over the years. A chimney cap:

a) will meaningfully reduce the amount of water and debris entering the chimney that can lead to very costly internal repairs,

b) will act as a spark arrestor and help prevent floating embers from causing a fire, and

c) will act as an animal guard to help keep birds, rodents, raccoons and other animals out.

Harky’s primarily installs stainless steel chimney caps and very few galvanized chimney caps. The primary issue with galvanized caps is they will rust – most will have a minimal/token warranty on them. Stainless steel chimney caps typically have a limited lifetime warranty on them – so leads to much higher customer satisfaction in our opinion.

#2 Mortar Crown is Cracked

The mortar crown is the cement part which covers the bricks on the very top of the chimney. Cracks in the chimney crown can occur from shifting of the structure, cement shrinkage dating back to when it was first installed, the natural weather elements wearing it down among multiple other reasons. The main issue is water/moisture can typically penetrate a mortar crown that is cracked and therefore it should be repaired to help prevent larger internal issues in the future.

If the cracks in the mortar crown are only modest, an overlay sealant might suffice. Even though it’s an overlay, Harky’s has access to a natural rubber overlay sealant that has a 15-year warranty on the product. Impressive product that carries an impressive warranty. If the cracks in the mortar crown are more serious, if it doesn’t appear there is metal support to structurally strengthen the mortar crown, and/or if there is wood/flammable material right around the flue area – Harky’s will likely recommend for the mortar crown to be removed/demo’d and rebuilt.

#3 Chimney Flashing Causing Leaks

Chimney flashing is the metal strip and components where the shingles meet the chimney. Flashing is typically made of aluminum or galvanized steel – one corrodes and the other rusts. Flashing will likely need to be repaired at some point – sometimes it will need to be ripped out and replaced and other times it will just need to be repaired. Harky’s has access to a natural rubber sealant for flashing that has a 7-year warranty on the product. Another impressive product that carries an impressive warranty.

#4 Bricks Are Spalling/Cracked Mortar Joints

Spalling is a common issue with bricks – especially chimney bricks above the roofline where they are fully exposed to the natural elements. Spalling occurs in brickwork when moisture is allowed to penetrate it. While colder climates are more prone to spalling as absorbed water is more likely to freeze and then expand and damage the brick – it’s still a common problem in Texas as there is a higher percentage of Mexican brick which is porous and typically a lower grade than brick in other states which physical attributes doesn’t require it to perform as well in freezing temperatures.

Water penetration and moisture can also erode the mortar joints (the mortar between the chimney bricks). Depending on how significant the eroded mortar joints are – tuckpointing (simply filling in the holes with new mortar) might be sufficient but in other scenarios where mortar is crumbling and filling in new mortar won’t suffice, repointing (grinding out the old mortar joints and then filling the whole joint in with new mortar).

Whatever the issues are – spalling bricks, porous brick, eroding mortar joints – applying a water repellent would be beneficial in these scenarios. We note we would shy away from water “sealants” in general – as it will seal/trap water that finds a way on the inside in and cause additional issues. Therefore sealants in general are bad for brick. Harky’s prefers a water “repellent”. Harky’s typically uses a siloxane-based water repellent. It not only repels water on the exterior brick, but it allows the brick to breath still therefore if water finds a way on the inside it will still allow it to exit and extend the life of your brick. Harky’s water repellent carries a 10-year warranty.

#5 Chase Covers are Rusted

Most chase covers (metal “pan” covering the full top of the chimney/chase) installed by builders are galvanized steel and will likely rust over time. Even with modest rust, condensation can accumulate enough to where water leaks down into the firebox area. Significant rust can cause holes and easily allow a meaningful amount of water into the chimney area.

We note a lot of wood-burning metal/prefab fireplaces that is exposed to a lot of water will likely rust as well and cause fire/carbon monoxide hazards. Therefore it’s important to replace chase covers that are starting to rust in our opinion. Harky’s primarily installs stainless steel chase covers with limited lifetime warranties on the product given it leads to a much higher customer satisfaction in our view. Many times galvanized chase covers installed have no or a token warranty against rust and the homeowner could be stuck purchasing another chase cover in the near future.