Home › Common Problems › Stair-Step Cracks in Brick Walls
Stair-Step Cracks in Brick Walls
in Nashville, TN
Stair-step cracks in a brick wall follow the mortar joints diagonally, like steps going up a staircase. They're usually a sign that the foundation under that part of the wall has moved. Nashville's clay-heavy soil swells and settles with every wet and dry season, and that movement adds up over the years in homes built before 2000. The crack itself isn't the problem — it's what caused it that matters.
Quick Answer
Stair-step cracks follow the mortar joints in a diagonal zigzag pattern up a brick wall. They happen when one part of the foundation sinks or shifts and the other part stays put — the wall cracks along the weakest path, which is the mortar. In Nashville, the heavy clay soil is a common cause because it shifts with moisture changes. A small crack that's not growing may just need repointing, but a wide crack or one that keeps opening needs a foundation inspection right away.
Telltale Signs
Warning Signs to Watch For
- A diagonal crack running in a zigzag pattern through mortar joints on a brick wall
- Cracks wider at the top than at the bottom, or vice versa
- Doors or windows near the crack that are sticking or won't open and close smoothly
- The crack is growing — you can tell because it's wider than it was last season
- Multiple cracks appearing at the corners of windows or door openings
- Interior drywall cracks directly above or below where the exterior crack appears
Root Causes
What Causes Stair-Step Cracks in Brick Walls?
Differential Foundation Settlement
Nashville's clay soil doesn't settle evenly across a foundation. One corner of a house may sit over soil that compresses more than the rest — common in areas of Southeast Nashville where fill was brought in during development. That corner sinks and the brick wall above cracks diagonally as one section drops relative to the other.
The Fix
Helical Pier Foundation Stabilization
A helical pier is a steel shaft screwed down through unstable soil until it reaches solid bearing ground. It's attached to the foundation to stop the movement. Once the movement stops, the crack can be repointed.
Soil Shrinkage in Dry Seasons
Nashville summers can be dry enough that the clay soil under a foundation shrinks and pulls away from the footing. The 2007 and 2012 droughts caused a wave of new foundation cracks across Middle Tennessee. When the soil shrinks unevenly under a house, sections of the foundation drop and the brick wall above cracks in a diagonal line.
The Fix
Soil Moisture Management and Crack Repair
Consistent moisture near the foundation — through grading, gutters, and sometimes a soaker system during dry spells — keeps the soil from shrinking unevenly. After the movement is controlled, the crack is repointed.
Tree Root Foundation Undermining
Large tree roots pull moisture from the soil near a foundation. In established Nashville neighborhoods like Forest Hills and Belle Meade, mature hardwoods sit close to houses built decades ago. When roots dry out the soil under one corner of a house, that corner settles and a stair-step crack opens above it.
The Fix
Root Management and Pier Support
The tree situation is assessed, the drying effect on the soil is addressed by root barriers or tree management, and the affected foundation corner is stabilized with piers before the crack is repaired.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | Differential Foundation Settlement | Soil Shrinkage in Dry Seasons | Tree Root Foundation Undermining |
|---|---|---|---|
| Crack is wider at the top and tapers at the bottom | |||
| Crack appeared or got visibly worse during a dry summer | |||
| Crack is at the corner of the house closest to a large tree | |||
| Doors and windows near the crack started sticking suddenly | |||
| Crack was stable for years then opened up after a very dry summer | |||
| Same crack appears on the inside wall directly behind the exterior crack |
Free Inspection
Get a Diagnosis in Nashville
An on-site inspection is the only way to confirm which cause applies to your property. Free, no obligation.
(629) 228-9821Free on-site inspection
Written estimate before work starts
Serving Nashville & surrounding areas
Other Problems
Services That Fix This
Also Helpful