Chimney Crown Repair in Connecticut

The crown is the slab that caps the masonry at the top of a chimney, sloping away from the flue so rain runs off the stack rather than sitting on it. On a well-built chimney it overhangs the brickwork with a drip edge, so water falls clear instead of running down the face.

It fails for two reasons. The first is that a great many crowns were never built properly — a thin skim of mortar troweled flat across the top, with no slope, no overhang and no reinforcement. That cracks within a few years and was always going to.

The second is freeze-thaw, the same mechanism that opens mortar joints. Water sits in a hairline crack, freezes, widens it, and the process repeats until the crack goes right through. Once it does, water is going directly into the core of the stack — between the flue liner and the masonry, where it has nowhere useful to go.

A sound crown with isolated cracking can be repaired: the cracks cleaned out and filled, and a flexible crown coating applied over the whole surface to bridge hairline movement. That is a real repair with a real life, and it is much less work than replacement.

A crown that has broken up, or one that was never formed correctly, is recast. The old material comes off and a new crown is formed in reinforced concrete with a proper slope, an overhang past the brick face, a drip edge underneath it, and an expansion joint around the flue tile so the crown and the liner can move independently — which is what stops the next crack.

Repair and replacement are one buying decision, which is why one page covers both. What decides it is the condition of what is there, and that needs someone at the top of the stack to look.