Chimney Crown Repair in the Seattle Area, WA.

The crown is the sloped concrete slab that covers the top of a masonry chimney, around the flue tiles. Its job is to shed rain away from the brickwork underneath. A crown built correctly is reinforced concrete, at least a couple of inches thick, sloped from the flue outwards, projecting past the face of the chimney with a drip edge, and separated from the flue tiles by an expansion joint so the tiles can move when they heat without splitting it.

Most of the crowns on older Puget Sound chimneys are none of those things. They are a thin layer of mortar troweled flat across the top, flush with the brick, with the flue tiles set hard into it. Mortar is not concrete, it is thin, it is flush so water runs straight down the face instead of dripping clear, and the tiles crack it from the inside as they expand. By the time anyone looks, it has a map of cracks and the brickwork below is soaking up everything that falls on it.

That matters more than it sounds. The whole stack above the roofline is exposed on four sides with nothing behind it, so water entering from the top has nowhere to go but into the masonry – where it freezes and takes the faces off the brick. A cracked crown is the single most common reason we are called to repair spalling on an otherwise sound chimney. Small cracks can be sealed with a flexible crown coating; a crown that is broken up or built flush gets cast again properly.