Is Your Chimney Cracking, Spalling, Leaning or Rotting?

The problem family: water plus freeze-thaw

Brick and mortar are strong when dry. The Brick Industry Association's Technical Note 18 describes what happens otherwise: moisture in saturated brick freezes, expands and, repeated enough times, causes cracking, spalling and disintegration. Seattle gets about 60 days a year where the temperature touches freezing but only about four that stay below freezing all day, which means a wet chimney crosses the freezing line again and again each winter. Moss, which spreads fastest here from October through April on shaded surfaces, holds extra water against the brick. The result is the familiar list: spalled faces, sandy joints, cracked crowns and, on framed chimneys, rotted sheathing.

How to tell which sub-problem you have

Flaking or popped brick faces

That is spalling. The outer face of the brick has sheared off, usually on the weather side or near the top. A few spalled bricks are a repair; a band of them across the whole top means the crown or cap failed long ago and the upper courses may need to come down and be rebuilt. Either way, the top has to be made watertight first or the new work fails the same way.

Crumbling, recessed or missing mortar

Failed joints let water straight into the core of the chimney. Joints that are recessed but the brick is sound can be cut out and repacked. Joints that are gone, with brick loose enough to move by hand, are a structural problem.

A stack that leans, or a gap between chimney and siding

Stop using the fireplace and call us the same day. A leaning stack above the roofline is a falling hazard in wind, and a gap at the house wall means the chimney is moving independently of the home. This needs eyes on it before the next storm.

A siding-clad chimney that is soft, stained or sagging

That is a framed chase, not masonry, and the enemy is rot. A rusted chase cover lets water down inside the framing for years before the siding shows it. Localized rot at the top is a chimney chase repair: cut out the bad material, reseal, new trim and cover. Widespread rot, sagging or framing you can push a screwdriver into is a chimney chase rebuild, starting at $299, which means new framing to proper clearances, sheathing, housewrap, siding and a new cover and cap.

What to do first

• Photograph the chimney from the ground on each side. Zoom on the top few courses and the roofline joint.
• Check the attic, if you can reach it safely from inside, for staining where the chimney passes through.
• Do not light a fire if anything is leaning, loose or separated.

Then call 206-453-2045. Our chimney repair page is the broad entry point: we diagnose first, then quote the specific fix, whether that is top work, flashing, firebox or the chase. Every quote is free, and if another company already gave you one, we will match it and take 10 to 25 percent off. Our free second-opinion quote is especially useful here, because "tear it down and rebuild" is sometimes right and sometimes the expensive answer to a crown problem.

Order of work matters

We always seal the top before restoring the sides, because rebuilding brick under a cracked crown just gives the water a fresh target. If you are not sure how bad it is, start with a chimney inspection; the camera shows whether the damage is skin-deep or has reached the flue. If you are not happy, we are not done.