What is the term for the tapered layer of mortar often found at the top of a chimney?

The correct term for the tapered layer of mortar often found at the top of a chimney is known as a cement wash. This layer serves several important purposes: it helps to shed water, preventing moisture from penetrating into the chimney structure, and it contributes to the overall aesthetic of the chimney, giving it a finished appearance.

Cement wash is specifically designed to be slightly sloped to ensure that rainwater runs off rather than pooling on top of the chimney. This slope is crucial for preventing water damage, as standing water can lead to degradation of both the mortar and the chimney materials over time.

While flashing refers to the waterproof material used to direct water away from critical areas of the roofing system, and a chimney cap is an accessory that covers the top of the chimney to prevent water, animals, and debris from entering, neither of those terms describes the tapered mortar layer itself. Mortar joints are the spaces between masonry units filled with mortar, but they do not specifically refer to the protective layer at the top of the chimney.