Chimney crown
The chimney crown, also referred to as the crown wash, is the top element of a masonry chimney which makes it highly vulnerable to weathering & water penetration. It covers and seals the top of the chimney from the flue liners to the chimney edge. It also prevents water from seeping into the masonry below.

Water damaged or cracked chimney crowns can lead to costly chimney repairs. A proper chimney crown should be constructed and formed so it provides an overhang, or drip edge, projecting beyond all sides of the chimney. This drip edge directs the runoff from the crown away from the sides of the chimney, helping prevent erosion of the brick and mortar in the chimney's vertical surfaces.
In some cases of chimney crown damage, there are other options for repair such as  modern waterproof, non-shrinking, cement like coatings for repairing damaged mortar crowns that work great called Crowncoat.

Growing Ivy on your chimney.

Ivy growing on the exterior of a chimney or house provides a decorative appeal. However, plants can cause extensive masonry damage to your chimney leading to stucture instability & safety hazards. Keep in mind that these plants have to anchor into the masonry. When this happens, it can be just  like having thousands of tiny nail holes in your mortar joints. These small holes open an entry to moisture that can penetrate through the chimney causing deterioration of the mortar and brick. This weakens the structure over time. Plants can also encourage mold and mildew growth.

We recommend homeowners have the vegitation removed and call a chimney sweep for an inspection of the structure's stability & for hidden damages or deterioration. If no repairs are needed, we recommend that the masonry & brick be treated with Chimney Saver Solution to protect the chimney from further damage, whether it may be due to the "freeze & thaw cycle" of winter or plant life.