Can cracked mortar cause basement leaks?

By Jake Wiles, owner · The Best Caulking & Restoration of Omaha · Updated August 2026

Yes — and in older Omaha neighborhoods it's one of the most common reasons a basement gets wet. Brick, limestone and block foundations are only as waterproof as the mortar between the units. When those joints crack, recede or crumble, every rain and every snowmelt has a path straight through the wall.

How the water gets in

1. Mortar fails at the grade line. The bottom two feet of the wall take splash-back, snow and wet soil. Mortar there wears first.
2. Water enters the joint. Capillary action and hydrostatic pressure push water through any open joint — it doesn't need a visible hole.
3. Freeze-thaw widens the gap. Water in the joint freezes, expands, opens the joint. Repeat fifty times a winter.
4. It shows up inside. A damp line along the base of the wall, efflorescence (white staining), a musty smell, or a puddle after a storm.

How to confirm it's the mortar

• Where does it show up? Leaks from failed mortar usually track a specific wall or corner — the one nearest a downspout or the low side of the lot.
• What does the outside look like? Go look at the same wall from outside. Crumbling or recessed joints at the grade line are the smoking gun.
• When does it leak? During and right after rain, or during a thaw: surface water through the wall. Days after rain, or constantly: likely a water table or drain tile problem.
• Is it brick, stone or block? Poured concrete walls leak through cracks and tie holes; masonry walls leak through joints.

The fix — outside first, then inside

1. Repoint the joints

Grind out the failed mortar and repoint to full depth. This is the actual repair — everything else is a band-aid without it. Brick foundation repair →

2. Fix the water source

Extend downspouts, regrade so the soil slopes away from the house, clear window wells. Cheap and essential.

3. Seal or waterproof the wall

Once the joints are solid, we apply a commercial-grade waterproofing on the inside (or outside where we can excavate) so the wall stops wicking. Basement waterproofing →

What doesn't work

Waterproof paint over failed mortar. Hydraulic cement smeared over crumbling joints. Caulk in a masonry joint. All three trap water in the wall instead of keeping it out, and all three make the eventual repair bigger. If a contractor's only plan is to coat the inside without touching the joints, get a second opinion.

One of our reviewers called three companies about a basement leak; Jake and Jordan came the day she called, ground out the defects, sealed the cracks and waterproofed the wall — and the other two companies later said the work was very well done and should take care of the problem. That's the standard.