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Fix a mortar that is cracked

We'll confirm the crack type, rule out structural damage, then repoint the joints with new mortar—or tell you when to call a pro.

Troubleshooting · Home maintenance
2–4 hours (plus cure time)
What you'll need
  • Mortar rake or cold chisel and hammer
  • Type N or type S mortar mix (or pre-mixed)
  • Pointing trowel
  • Jointer or concave tool
  • Stiff brush
  • Spray bottle or water source
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Steps

Goal: Confirm the crack type, rule out structural damage, then repoint the joints or call a pro.

  • Inspect the wall. Note whether the crack is hairline, crumbling, or missing—and whether bricks or blocks are loose or shifting.
  • Good: Crack visible—proceed to Check if it suggests structural issues.
  • Bad: Wall looks intact—you may have a different problem (brick spalling, efflorescence).

Check if crack suggests structural issues

Goal: Rule out foundation or structural damage before repointing.

  • Stair-step cracks in brick or block often indicate foundation movement. Horizontal cracks can mean soil pressure. Cracks wider than 1/4 inch or loose bricks need a pro.
  • If doors or windows nearby stick or bind, that can signal settling. Call a mason or foundation professional to assess.
  • Good: Crack is hairline or minor crumbling—proceed to Repoint path.
  • Bad: Stair-step, horizontal, or loose bricks—call a pro.

Repoint path

Goal: Remove old mortar and fill with new mortar so the joint is sealed and stable.

  • Remove old mortar with a mortar rake or cold chisel and hammer to a depth of about 3/4 inch. Do not remove more than 1 inch. Brush out debris.
  • Dampen the joint with a spray bottle—damp but not dripping. If too wet, the mortar may not bond; if too dry, it will suck moisture and weaken.
  • Mix type N or type S mortar per the product label. Type N for most above-grade walls; type S for below-grade or high-load areas.
  • Pack mortar into the joint with a pointing trowel. Apply in small sections. Overfill slightly so you can tool the joint.
  • When the mortar is thumbprint-hard (soft but not wet), use a jointer to shape the joint to match the surrounding joints. Match the existing profile (concave, V, or flat). Brush off excess mortar.
  • Protect from rain and direct sun for 24–48 hours. Mist lightly if needed in hot weather.
  • Good: The joint is filled and the surface matches—done.
  • Bad: Crack reappears or mortar fails—call a pro to assess.

When to get help

Call a mason or foundation professional if:

  • The crack is stair-step (follows mortar joints in a step pattern).
  • The crack is horizontal.
  • The crack is wider than 1/4 inch or growing.
  • Bricks or blocks are loose or shifting.
  • You have repointed and it keeps failing.

Confirm you have assessed the crack type before calling. For related fixes, see Fix a driveway that has cracks or Fix a wall that has a crack.

Verification

  • The mortar joint is filled and the surface matches the surrounding joints.
  • The repair does not crack or crumble after cure time.
  • The joint does not reappear after the patch dries (if it does, call a pro).
  • No loose bricks or blocks near the repair.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm symptom Note the crack pattern—hairline, crumbling, or missing—and whether bricks are loose.
  2. Rule out structural Stair-step, horizontal, or wider than 1/4 inch—call a pro. Hairline or minor crumbling—proceed to repoint.
  3. Rake out old mortar Remove old mortar to 3/4 inch depth. Clean and dampen.
  4. Repoint and tool Mix mortar, pack into joints, tool to match.
  5. Call a pro Structural crack or loose bricks—call a mason or foundation professional.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Crack pattern (hairline, crumbling, stair-step, horizontal)
  • Whether bricks or blocks are loose or shifting
  • Joint depth and condition
  • Steps already tried

Is the mortar cracked or crumbling?

Inspect the joints between bricks or blocks. Note whether the crack is hairline, crumbling, or missing. Check if bricks are loose.

Inspect the wall. Yes: Mortar visible—proceed to check if it suggests structural issues. No: If the wall looks intact, you may have a different problem (brick spalling, efflorescence).

Yes No

You can change your answer later.

Is the crack stair-step, horizontal, or wider than 1/4 inch? Are bricks loose?

Stair-step cracks in brick or block, horizontal cracks, or loose bricks can indicate foundation or structural issues.

Check the crack pattern. Stair-step: Follows mortar joints in a step pattern—often foundation. Horizontal: Can mean soil pressure. Wider than 1/4 inch: May be structural. Loose bricks: Call a pro. Yes: Call a mason or foundation pro. No: Crack is hairline or minor crumbling—proceed to repoint.

Yes No

You can change your answer later.

Rake out, repoint, and tool the joint

Remove old mortar to 3/4 inch depth. Clean and dampen. Apply type N or S mortar. Tool to match.

Rake out old mortar with a mortar rake to 3/4 inch depth. Clean and dampen the joint. Mix type N or type S mortar. Pack into the joint with a pointing trowel. When thumbprint-hard, use a jointer to shape. Match the existing profile. Protect from rain and sun for 24–48 hours. Good: Repair complete—done. Bad: Crack reappears or mortar fails—call a pro to assess.

Done

Call a mason or foundation pro

Call a mason or foundation professional if: the crack is stair-step, horizontal, or wider than 1/4 inch; bricks or blocks are loose or shifting; or you have repointed and it keeps failing. Confirm you have assessed the crack type before calling.

Done

Different problem

If the wall looks intact, you may have a different problem—brick spalling, efflorescence, or water staining. See the relevant guide.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why does mortar crack?
Common causes: age, freeze-thaw cycles, moisture, and settling. Hairline cracks and minor crumbling are often cosmetic. Stair-step cracks, horizontal cracks, or loose bricks can indicate foundation or structural issues.
Can I fix cracked mortar myself?
Yes. Hairline cracks and minor crumbling in stable brick or block joints can be repointed with type N or S mortar. If the crack is stair-step, horizontal, wider than 1/4 inch, or bricks are loose, call a mason or foundation pro first.
When should I call a pro for cracked mortar?
Call a mason or foundation professional if: the crack is stair-step (follows mortar joints in a step pattern), horizontal, wider than 1/4 inch, or bricks or blocks are loose or shifting. Structural damage needs assessment before repointing.

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