The brick on my chimney is flaking and crumbling

Likely causes, most common first

What breaks the face off chimney brick, most common first.

1. Most common

   Water in the brick froze and pushed the face off

   The sign: Shallow, dish-shaped scars where the outer skin has popped, worst above the roof on the side the weather hits, with red grit in the gutter.

   The fix: Spalled brick is cut out and replaced one at a time and the joints around them repointed, before the water path is closed. Tuckpointing and Masonry Repair, from $449

2. Common

   Soft old brick that drinks every rain

   The sign: Faces crumbling to sand rather than popping in flakes, on an older chimney, often where a softer interior brick was used on the outside.

   The fix: After the worst brick is replaced and the masonry has dried, a breathable repellent sheds rain before the brick can drink it. Chimney Waterproofing, from $349

3. Common

   A crown or cap that has let water into the stack for years

   The sign: Spalling that starts at the top course and works down, a crown with chunks missing or no cap, with the lower chimney still sound.

   The fix: A new crown with an overhang and a cap stop the soaking from above, and the top courses are rebuilt as needed. Chimney Crown Repair, from $349

4. Less common

   A flue that is wet from the inside

   The sign: Spalling on the inside face of the chimney in the attic or basement, or on a chimney venting only a water heater since the furnace went.

   The fix: A camera run shows a flue condensing and scaling, and a liner matched to the water heater dries the stack from inside. Chimney Inspection, from $129

5. Less common

   Too much of the stack is gone to patch

   The sign: Spalling on every face above the roof, missing brick, daylight through the joints, or a tilt you can spot from the sidewalk.

   The fix: The chimney is taken down to sound brick, usually the roofline, and rebuilt with a liner, a proper crown and a cap. Chimney Rebuild, from $2499

Two minutes of safe checks

What to look for from the sidewalk and the yard, with both feet on the ground.

• Walk the drip line of the chimney and look for brick flakes, red grit or whole brick on the ground, in a window well or at the base of a downspout.
• From across the street, compare the four faces: one face means weather, all around the top means the crown or cap, from the roof down means years of soaking.
• Check whether the chimney is straight against the roofline and the wall; a lean, a gap at the siding or a crack up a corner moves this from a repair to a safety call.
• Zoom in on the top with a phone or binoculars: a crown with missing chunks or a bare flue with no cap is often where the water started.
• If the chimney passes through an attic you can walk into or a basement, look at its inside faces; spalling indoors means the flue itself is wet.

Nothing on this list needs a ladder, the roof or a lit fire. Leave those to the visit.

Why Portland brick spalls

Brick spalls when it is wet on a night that freezes, and the airport normals give this area roughly 32 nights at or below freezing a year, nearly all of them inside the five wettest months. The brick is rarely dry when it freezes.

Water in a brick expands as it freezes and pushes outward, and the face, the thinnest part, pops off. The scar left behind is softer and more open than the face was, so the next winter takes the brick faster.

The stack above the roof takes rain from every side with nothing to shelter it, and the side facing the storms takes the most. Toward Troutdale and Gresham the Gorge east wind drives rain into the east face, and a stack uncapped for decades has been wet from inside as well.

When crumbling chimney brick is a safety call, not a repair quote

Keep people and cars away from the chimney and call now when any of these is true.

• Whole brick, not flakes, has landed on the roof, in the gutter or on the ground; the next one can land on a person.
• The chimney leans, has pulled away from the siding or shows a crack up a corner; it is likely unreinforced brick, and the next windstorm or quake may finish it.
• Spalling runs down into the attic or basement faces; the flue is wet inside and may be cracked, so the fireplace and anything venting into it stay off until a camera run clears it.
• Pieces of clay tile or brick are landing in the firebox; the liner is breaking up, and a fire in that flue heats framing it was never meant to touch.

What repairing spalled chimney brick involves

The repair replaces what failed and then takes away the water that failed it; one without the other does not last.

1. Count the damage

   We photograph every face, tap the suspect brick, check the crown, cap and flashing and probe the joints. The count decides between replacing brick, rebuilding the top courses and taking the stack to the roofline.

2. Replace and repoint

   Spalled brick is cut out, matched as closely as old Portland brick allows and set in a mortar that gives before the brick does; the joints around the repair are raked and repointed at the same time.

3. Close the water path

   A new crown with an overhang and a drip edge, a screened cap and sound flashing go on before the brick is treated, since repellent on a stack still soaking from the top does nothing.

4. Protect the face

   After a dry stretch, a breathable water repellent goes on the exterior brick. Where the spalling reached the inside, the camera checks the liner, and the photos of each step come with the posted price.

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