By Johnathan Mason, Ace Chimney Service.
Brick outlasts the mortar between it. On most chimneys the brick is fine and the joints are the part quietly failing, and once mortar is gone the whole stack is taking on water. Around Wonder Lake, where chimneys sit exposed to open wind coming off the water, joints tend to go on the weather side first.
What tuckpointing is
Tuckpointing — also called repointing — means grinding or raking out the deteriorated mortar to a consistent depth and packing fresh mortar into the joint. It is not smearing new mortar over the old surface. Done as a surface coat it fails within a season or two, because the failed material underneath is still there holding water.
How to spot joints that are done
Run a key or a screwdriver along a joint. If it gouges out sandy material without much resistance, the mortar has lost its binder. Look for joints that are recessed well behind the face of the brick, for gaps you can see daylight or shadow in, for sand collecting on the roof or at the base, and for a chimney that looks like its top few courses are leaning or have shifted. Vertical cracks running through both brick and mortar are a different and more serious problem.
Why it happens faster on a chimney
A chimney is the most weather-beaten masonry on the house. It gets rain from every direction, has no roof over it beyond its own crown, and cycles through freeze and thaw far more often than a wall does because it is exposed on all four sides. Add heating gases inside and you get temperature swings that walls never see. That is why a chimney needs repointing long before the rest of the brickwork does.
Matching matters
New mortar has to suit the old brick. Modern high-strength mixes on soft historic brick cause the brick face to spall, because the joint becomes harder than the unit around it and stress goes into the brick instead of the mortar. Colour and joint profile also matter if you would rather the repair not announce itself. This is judgment work, not a bag off the shelf.
Sequence and season
Repointing pairs naturally with crown repair and waterproofing, and the order matters — joints first, then the crown, then any breathable water repellent. Mortar wants mild, dry weather to cure, so early autumn is a good window here and mid-winter is not. Getting water out of the masonry before the freeze-thaw season is the entire point. See our chimney repair page, or the full lineup on chimney services.
Ace Chimney Service is insured and bonded with 29 years in the trade, gives the price up front, and works seven days a week from 7 AM to 7 PM across Crystal Lake and McHenry County. Call (815) 320-0883.
Frequently asked questions
How do I know if my chimney needs tuckpointing?
Probe a joint with a key. Crumbling, sandy mortar, deeply recessed joints, or visible gaps mean the joints are past their service life.
Can I just smear new mortar over the old?
No. The failed material must be cut out to a proper depth first, or the repair debonds and falls out.
Does tuckpointing stop chimney leaks?
It removes one of the main entry paths. Leaks usually involve the crown and flashing too, so all three get evaluated together.
How long does repointing last?
Properly cut, matched, and packed joints last for decades on a chimney that also has a sound crown and cap.
Should I waterproof after tuckpointing?
A breathable masonry repellent applied after the joints are sound is a reasonable step. Never use a sealer that traps moisture inside.
Is repointing the same as rebuilding?
No. Repointing renews the joints. Rebuilding takes the chimney down to sound masonry and relays it, which is what leaning or badly cracked stacks need.
What time of year is best?
Mild, dry conditions. Early autumn and late spring suit our climate; hard freezes ruin fresh mortar.
Can I burn while the work is happening?
Hold off until the mortar has cured. It is usually a short wait and worth respecting.
Published September 4, 2026