Chimney and fireplace symptoms
Mortar is falling out between the bricks on my chimney
Mortar falling out of a Portland chimney has often been washed out by rain, worst above the roofline on the weather face, and the joints need repointing. Light no fires until the joints are probed, since loose mortar can mean loose brick.
Updated
What to do this week
Photograph the open joints from the ground on a dry day and note which face of the chimney they are on. Keep any mortar crumbs you find in the gutter spill or on the ground; the color and grit tell us what the last repair used. Hold off on fires until someone has probed the joints, since a stack shedding mortar can also shed brick.
Likely causes, most common first
Four things take the mortar out of a chimney joint, and the pattern on the brick usually says which one you have.
- Most common
Decades of rain have eroded the joints
The sign: Joints recessed deepest on the weather face above the roof, with mortar that rubs off as sand.
The fix: The failed joints are ground out to sound mortar and repointed with a mix matched to the brick. Tuckpointing and Masonry Repair, from $449
- Common
An earlier repair used the wrong mortar
The sign: Patches of hard gray cement standing proud of the brick, with the original joints beside them crumbling and brick faces popping off next to the patches.
The fix: The hard patches come out with the failed joints, and the whole face is repointed in a softer mortar that lets the old brick move and dry. Tuckpointing and Masonry Repair, from $449
- Common
Moss has rooted in the joints
The sign: Green cushions along the joints on the shaded face, and mortar that stays dark and damp for days after the rain stops.
The fix: After the moss is cleaned off and the joints are repointed, a breathable water repellent keeps the face from soaking through again. Chimney Waterproofing, from $349
- Common
Water is coming down from a cracked crown or a missing cap
The sign: The top few courses are the worst, the joints under the crown are hollow, and the rest of the stack looks sound.
The fix: The crown is patched or recast first, then the top courses are repointed, so the new mortar is not washed out from above. Chimney Crown Repair, from $349
- Less common
The joints have failed through the full depth of the wall
The sign: A brick that rocks when pushed, daylight through a joint seen from the attic, or mortar gone from both faces of the same course.
The fix: Repointing cannot hold brick that has already let go, so the stack comes down to sound courses and is relaid with a new crown. Chimney Rebuild, from $2499
Two minutes of safe checks
These checks take a few minutes from the yard, the basement and the attic hatch, and none of them needs a ladder.
- From the sidewalk, compare the weather face of the chimney with the sheltered face; recessed, shadowed joints on one side point to rain rather than age.
- After a wet week, look at the chimney brick inside the attic or an upstairs closet for a damp patch or a white bloom, which is water tracking in through open joints.
- Check the gutter below the chimney and the ground at its foot for mortar crumbs or brick chips, and keep whatever you find.
- From the lawn, check the crown and the cap: a crown with visible cracks or a flue with no cap means the water is also coming in from the top.
Why the mortar goes first above the roof and on the weather face
The part of the chimney above the roof takes rain on four sides with nothing sheltering it, so its joints wash out years before anything shows inside the house. The face toward the prevailing weather goes first.
Portland gets about two thirds of its yearly rain between November and March, and nearly all of its roughly 32 freezing nights fall inside those same months. Water sits in an open joint, freezes, and pries the joint a little wider each winter.
Many brick chimneys laid in the early 1900s across Woodstock, Alberta, Kenton and Montavilla were set in a softer mortar than the bagged mixes sold today. That mortar was meant to give way before the brick did, which is why you find mortar on the ground and not brick.
When repointing is enough and when the stack needs rebuilding
Repointing is the right repair while the brick is sound and the joints are open on the surface but still hold mortar deeper in. The failed depth is ground out, the joint is packed with new mortar, and the chimney stands as it was.
A rebuild starts to make more sense when brick is loose or spalled across whole courses, when the joints are open through the wall, or when the stack has started to lean. Repointing in that condition buys little time before the same joints open again around moving brick.
The answer comes from probing the joints and looking at the crown and flashing, which is why we price repointing from photos but confirm it on the roof. If the probe finds a rebuild, you hear that before any grinding starts.
What repointing your chimney involves
A tuckpointing visit follows this sequence, and the first step decides how far the rest goes.
Probing and photographing
We probe the joints on every face, measure how deep they are open, photograph the worst courses, and check the crown, the cap and the flashing, since those decide whether new mortar will last. A Level 1 look at the flue inside comes with it.
Grinding out the failed mortar
The open joints are ground or raked back to sound mortar, deep enough to give the new material something to hold, without cutting into the brick. The dust is rinsed out so the new mortar bonds to clean masonry.
Packing and tooling the new joints
Mortar matched to the old brick in color and hardness is packed into the joints in layers and tooled to the profile of the original. On an older chimney that means a softer, lime-rich mix rather than straight cement.
Crown, cap and water repellent
Once the joints have cured, the crown is sealed or recast as needed, an open flue gets a cap, and a breathable water repellent is applied to the brick above the roof. You get photos of the finished joints from the roof.
Loose or missing mortar: common questions
Is loose mortar on a chimney a safety problem or just a cosmetic one?
It is a water problem first and a safety problem if it is left. Open joints let rain into the brick and down into the house, and once the joints are open through the wall the brick above the roof can shift or fall. Repointed early it is routine; left for years it is a rebuild.
Can I fill the missing mortar on my chimney with caulk or a tube of mortar repair?
Not for long, and it can make the next repair harder. Caulk and tube mortar sit on the surface, trap water behind them and soon pop out. Proper repointing grinds the joint back to sound mortar and packs it full, which is what keeps the water out and the brick in place.
Why is the mortar falling out on only one side of my chimney?
Because that side faces the weather. Wind-driven rain hits the face toward the storms hardest, and in the east metro the east face takes it on Gorge wind days. The sheltered side stays drier and its joints last far longer. One bad face is the normal pattern, and it is repointed on its own when the rest is sound.
Does missing mortar on the outside of the chimney mean the flue inside is damaged too?
Often enough that we look. Water that has been running through open joints has often been running past the flue tiles as well, and a chimney with no liner has nothing between the open joint and the smoke path. A Level 1 look comes with the repointing visit, and a camera run follows if the joints were open through.
Should the chimney be waterproofed after the mortar is repointed?
Yes, once the new joints have cured, and only with a breathable repellent. A film-forming sealer traps water inside the brick, where freezing spalls it. A breathable repellent lets the brick dry outward while shedding rain, and it protects the new mortar on the weather face, which is where the next failure would start.
Related pages
Areas we cover for this
Calls about loose or missing mortar come in from Northwest District and Nob Hill, Sandy, West Linn and every other part of the metro we serve.
Ready to book a sweep?
Call with what the fireplace is doing, or text a photo of the opening and one of the chimney top, and we will name the service and its posted price before we come out.