How it works

A wash is built up with type N or type S mortar feathered from a high point at the flue tile down to the outer brick edge, creating a sloped surface that directs rainwater off the chimney. Because mortar lacks aggregate reinforcement and is bonded directly to the brick below, washes crack within a few years under thermal cycling and freeze-thaw stress. Once cracked, water penetrates the brick and saturates the masonry from the top down.

The functional difference between a wash and a crown is durability and water management. A crown overhangs the brick with a drip edge, so water falls clear of the masonry; a wash terminates flush with the outer brick face, so water runs directly down the chimney exterior. Sweeps document wash condition during a CSIA Level 1 inspection, and a deteriorated wash is one of the most common findings on chimneys built before 1990.

DFW context

Many DFW chimneys built in the 1960s through the 1980s use mortar washes rather than concrete crowns, and after multiple freeze-thaw cycles and the June 2025 hailstorms, those washes are visibly cracked or partially missing on hundreds of TSE service calls per year. The standard remediation is to chip out the failed wash, install bond-break collars around the flue tile, and pour a proper concrete crown with a 1-inch overhang.

Related terms

• [Crown](/glossary/crown/)
• [Crown coat](/glossary/crown-coat/)
• [Spalling](/glossary/spalling/)
• [Tuckpointing](/glossary/tuckpointing/)

Sources

• NFPA 211 (2024), Section 10.4.3
• CSIA Crown Construction Standard
• IRC 2021, Section R1003.9