The cap protects an opening
A cap is selected for the flue arrangement and the system it serves. Its fit, attachment, and condition matter. Missing or damaged components can leave an opening exposed. A cap should not be selected by appearance alone, because the chimney and appliance requirements also need to be considered.
The crown is part of the masonry top
The crown sheds water away from the top of the masonry. Its visible condition, edges, and relationship to the flue penetrations should be assessed together. Covering a crack with a surface product is not equivalent to rebuilding a failed crown, and a new cap does not repair deteriorated masonry beneath it.
A leak can have more than one route
Water seen indoors may involve the crown, a flue opening, masonry joints, or the roof-to-chimney connection. Keep a record of when the stain appears and whether the weather or wind direction seems relevant. Those observations are clues, not proof of a single entry point.
Ask for a component-by-component scope
An estimate should distinguish cap work from crown work and identify any separate roof, flue, or brickwork concerns. Ask which existing components will remain and how the proposed repair relates to them. That is a clearer basis for a decision than a single line labeled chimney waterproofing.
Leave roof access to the assessment
Photograph the chimney from a safe ground-level position. Do not climb to tighten a cap or inspect cracked material yourself. Report loose pieces or visible displacement when you contact the contractor so access and safety can be discussed before the visit.
