Repointing and Spalled Brick Repair for Old Chimneys

Mortar is meant to be the weak part of a brick wall. It wears away over the years so the brick does not have to, and every few decades it is raked out and replaced. That replacement is repointing. On a chimney in the Seattle area, where Sea-Tac averages about 39 inches of rain a year, the joints on the weather side of the stack usually go first.

Spalling is the next stage. Water soaks into the brick, freezes and pushes off the face. Once the hard outer skin is gone, the soft inside of the brick absorbs water faster still, and the damage speeds up each winter. Catching it while it is only the mortar is much cheaper than replacing brick. At the free inspection we show you which joints are worn, which bricks are starting to flake and which are still sound, and price each part separately.

Signs you need this

• Mortar joints that are recessed, sandy or missing
• Brick faces flaking or popping off in coin-sized pieces
• White, powdery staining on the brick
• Earlier repairs in gray mortar that look harder than the brick
• Gaps you can push a key or coin into

How we do it

1. Check the brick and mortarWe look at how deep the wear goes and whether earlier repairs used mortar that is too hard.
2. Rake out the jointsOld mortar is removed to a sound depth without chipping the edges of the brick.
3. Repoint with the right mixWe fill the joints with a mortar matched to the brick, softer and more lime-rich for older chimneys.
4. Replace spalled brickBadly spalled bricks are cut out and replaced with a close match, then the crown and flashing are checked.

Why does the type of mortar matter so much?

The National Park Service's guide to repointing, Preservation Brief 2, explains that mortar harder than the brick will not give as the wall moves, so stress passes into the brick and causes permanent damage such as cracking and spalling. It also says mortar must let moisture out, or the brick itself is damaged.

Many Seattle chimneys from the 1900s to the 1930s were laid in soft, lime-rich mortar. Repointing them with modern hard cement mortar is a common and costly mistake. We match the mortar to the brick, not the other way round.

What is the white stuff on my chimney?

That powder is usually efflorescence: salts that water carries out of the masonry and leaves on the surface as it dries. Preservation Brief 2 notes that salts building up inside masonry can make the surface spall off.

The powder itself brushes off. What matters is the water behind it. White staining tells us where water is moving through the chimney, which points to the joints, crown or flashing that need attention.

What do repointing and brick replacement cost?

Spot repointing a few rows is typically $500 to $1,200. Repointing the full stack above the roof is typically $1,200 to $2,500. Replacing spalled brick is typically $1,000 to $3,500, depending on how many bricks and how high the work is.

In Seattle's historic districts, such as Harvard-Belmont, repair in kind with matching materials needs no Certificate of Approval, but the board coordinator must confirm it before work starts.