What chimney waterproofing can and cannot do
A compatible masonry treatment can reduce liquid-water absorption while allowing vapor to escape. It does not repair failed flashing, an open crown crack, missing mortar, a damaged cap, or structural movement. For fire, smoke entering the home, or a carbon-monoxide alarm, evacuate and call 911. If gas is smelled or suspected, do not operate switches or electronics or create a flame; leave immediately, then call 911 and the gas utility from outside. Contact a contractor only after responders or the utility clear the property as safe.
Product selection depends on the substrate
The proposal should identify the product, treated surfaces, preparation, application method, coat requirements, coverage limitations, and manufacturer cure conditions. Vapor permeability and compatibility with the existing brick, mortar, stucco, coatings, and prior treatments matter more than a generic material promise.
Timing and reapplication
Application requires suitable surface and weather conditions. Reapplication timing depends on the product instructions, exposure, substrate condition, preparation, and observed performance; it should not be presented as a fixed schedule. Ask how the treated surface will be evaluated during future maintenance.
Written scope before application
Confirm cleaning, crack or joint repairs, excluded leak sources, adjacent-surface protection, cure requirements, price, and any applicable warranty terms. If waterproofing is part of claim-related work, the insurer decides coverage and documentation requirements.