How to Fix a Crack in a Brick Wall: Tuckpointing, Crack Filler, and When to Call a Pro

Cracks in brick walls are a common sight in older homes and buildings — but like concrete cracks, they range from purely cosmetic to genuinely structural. A crack running through the mortar joints is usually a maintenance issue. A crack running through the bricks themselves is a more serious sign of stress. Knowing the difference, and choosing the right repair method, is what separates a fix that lasts from one that fails within a season.

This guide covers how to diagnose brick wall cracks, the correct repair method for each type, and when the damage is beyond DIY territory.

Understanding Brick Wall Construction

Brick walls consist of two components: the bricks themselves and the mortar joints between them. Mortar is intentionally the weaker of the two — it's designed to absorb movement and stress so the bricks don't crack. This means most brick wall cracks appear in the mortar joints rather than through the bricks, which is actually good news: mortar repairs (called tuckpointing or repointing) are straightforward DIY work.

Cracks through the bricks themselves indicate forces strong enough to overcome the mortar's sacrificial role — a sign of more significant structural stress.

Types of Brick Wall Cracks

Mortar joint cracks — Cracks running along the mortar between bricks. The most common type. Usually caused by mortar aging and weathering, minor settling, or freeze-thaw cycling. Cosmetic to minor structural; repairable with tuckpointing.

Stair-step cracks — Cracks that follow the mortar joints in a diagonal stair-step pattern. Often caused by differential settling — one section of the foundation settling more than another. May be cosmetic if narrow and stable; warrant professional evaluation if wide or growing.

Vertical cracks through bricks — Cracks running vertically through both mortar and brick. Often caused by thermal expansion, lintel failure above openings, or significant settling. Require professional evaluation.

Horizontal cracks — Cracks running horizontally through mortar joints. Can indicate lateral soil pressure (in retaining walls or basement walls) or lintel failure. Consult a structural engineer.

Cracks with displacement — Any crack where one side is higher, lower, or further out than the other. Indicates significant structural movement. Do not repair yourself — consult a structural engineer immediately.

When to Call a Professional

Repair yourself only if:

• The crack runs through mortar joints only (not through bricks)
• The crack is narrow (under ¼ inch) and stable
• There's no displacement — both sides of the crack are flush
• The crack hasn't grown in 2–3 months
• There's no water infiltration through the crack

Consult a structural engineer if the crack runs through bricks, is horizontal, shows displacement, is growing, or is accompanied by other structural symptoms.

What You'll Need

• Concrete crack filler — DAP Concrete Crack Filler (1.62 lb) works well for narrow mortar joint cracks — it's flexible, bonds to masonry, and can be painted over once cured.
• Finishing trowel — The 11"x5" Stainless Steel Finishing Trowel for applying and smoothing mortar in tuckpointing repairs.
• Putty knife set — The Rerdeim 5-Piece Putty Knife Set for cleaning out joints and applying filler in narrow cracks.
• Sanding sponge set — The 24-Piece Sanding Sponge Set for smoothing cured filler if needed.
• Pre-taped masking film — The Pre-Taped Masking Film (2-Roll Pack) to protect surrounding surfaces during repair work.

Method 1: Filling Narrow Mortar Cracks with Crack Filler

For hairline to narrow cracks (under ¼ inch) running through mortar joints, a flexible masonry crack filler is the fastest and most durable solution.

Step 1: Clean the crack
Use a wire brush, vacuum, or compressed air to remove all loose mortar, dust, and debris from the crack. The joint must be clean and dry for the filler to bond properly. Remove any old paint or sealant that's peeling away from the crack edges.

Step 2: Dampen the joint
Lightly mist the crack and surrounding mortar with water. Old mortar is porous and will aggressively absorb moisture from the filler, causing it to dry too fast and crack. Dampening slows this absorption and improves bond strength.

Step 3: Apply crack filler
Apply DAP Concrete Crack Filler directly into the crack, pressing it firmly with a putty knife from your set to fill completely. Overfill slightly — the filler shrinks slightly as it cures. Work in sections along the crack length.

Step 4: Smooth flush
Before the filler fully sets, drag a putty knife blade flat across the joint to smooth the filler flush with the surrounding mortar surface. For wider joints, use your finishing trowel for a cleaner, more even finish.

Step 5: Allow full cure
Allow 24–48 hours for full cure before painting or applying any sealer. Keep the repair dry during this period.

Method 2: Tuckpointing (Repointing) Deteriorated Mortar Joints

When mortar joints are cracked, crumbling, or recessed more than ¼ inch from the brick face, tuckpointing — removing the old mortar and replacing it with fresh mortar — is the correct repair. This is more involved than crack filling but produces a far more durable result.

Step 1: Remove deteriorated mortar
Use a cold chisel and hammer or an angle grinder with a mortar-raking blade to remove deteriorated mortar to a depth of at least ¾ inch. Don't go deeper than necessary — you want to remove the damaged material without disturbing the brick bond. Brush away all dust and debris.

Step 2: Dampen the joint
Thoroughly dampen the cleaned joint with water. This is critical — dry brick and mortar will absorb water from the fresh mortar too quickly, weakening the bond and causing the new mortar to crack prematurely.

Step 3: Mix and apply new mortar
Mix mortar to a stiff, workable consistency — it should hold its shape when squeezed but not be crumbly. Pack the mortar firmly into the joint in layers, filling to about ¾ of the joint depth first, then finishing to the surface. Use your finishing trowel to pack and smooth the mortar. Match the mortar color to the existing joints as closely as possible — mortar color varies significantly between homes and ages.

Step 4: Tool the joint
Before the mortar fully sets (typically 30–60 minutes after application), tool the joint to match the profile of the existing mortar joints. Common profiles include concave (rounded inward), flush, and weathered (angled to shed water). Use a jointing tool or the edge of a putty knife to create the profile.

Step 5: Cure slowly
Keep the new mortar damp for 3–5 days by misting lightly with water once or twice a day. This slow curing process (called moist curing) produces stronger, more crack-resistant mortar. Avoid repointing in direct sunlight or high heat, which causes the mortar to dry too fast.

Matching Mortar Color

One of the biggest challenges in brick wall repair is matching the color of existing mortar, which varies by age, composition, and weathering. A few tips:

• Test your mortar mix on a small, inconspicuous area and allow it to fully cure before assessing the color match — wet mortar is always darker than cured mortar.
• Most home improvement stores carry mortar in several standard colors (gray, buff, white). Mix colors to get closer to your existing mortar if needed.
• Mortar color can be adjusted with pigments specifically designed for masonry.
• Accept that a perfect match is rarely achievable — weathered mortar has a patina that fresh mortar can't replicate immediately. The color will blend over time as the new mortar weathers.

Preventing Future Brick Wall Cracks

• Seal the brick surface. A quality masonry sealer reduces water infiltration and the freeze-thaw cycling that deteriorates mortar over time.
• Maintain gutters and drainage. Water pooling against brick walls accelerates mortar deterioration. Ensure gutters are clean and downspouts direct water away from the wall.
• Repoint proactively. Don't wait for mortar to crack before repointing. Mortar that's recessed more than ¼ inch from the brick face is allowing water infiltration and should be repointed even if not visibly cracked.
• Address vegetation. Ivy and other climbing plants look attractive on brick but their roots penetrate mortar joints and accelerate deterioration. Remove vegetation from brick walls and seal any joint damage they've caused.

Frequently Asked Questions

Can I use regular caulk to fill brick mortar cracks?
Standard silicone or latex caulk is not designed for masonry and won't bond properly to brick or mortar. Use a product specifically formulated for masonry, like DAP Concrete Crack Filler, or proper mortar for tuckpointing.

How do I know if my brick wall crack is structural?
Key warning signs: the crack runs through bricks (not just mortar), there's visible displacement (one side higher or further out than the other), the crack is horizontal, or it's growing over time. Any of these warrant professional evaluation before repair.

How often does brick mortar need to be repointed?
Quality mortar in a well-maintained wall can last 25–50 years. Mortar in exposed, high-moisture, or freeze-thaw environments may need repointing every 15–20 years. Inspect mortar joints annually and repoint any that are recessed, crumbling, or cracked.

Can I paint over repaired brick mortar?
Yes, once the repair is fully cured (48–72 hours for crack filler, 28 days for new mortar). Prime with Bulls Eye 1-2-3 before painting for proper adhesion on the alkaline masonry surface.

What's the difference between tuckpointing and repointing?
Technically, repointing means removing old mortar and replacing it with new mortar. Tuckpointing is a specific technique where a thin line of contrasting-color mortar is applied over the joint to create the appearance of fine, precise joints. In common usage, the terms are often used interchangeably to mean mortar joint repair.

Final Thoughts

Brick wall crack repair is one of those home maintenance tasks that rewards early action. A narrow mortar crack caught early is a 30-minute repair with crack filler. Left for years, it becomes a full tuckpointing job — and if water infiltration has damaged the brick or underlying structure, the repair becomes significantly more complex and expensive. Inspect your brick walls annually, address mortar deterioration proactively, and use the right material for the crack type. Done right, a brick wall repair is nearly invisible and lasts for decades.