Cracks Appearing on Walls After the Rainy Season — Normal or Dangerous? (A Ghanaian Homeowner’s Guide)
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CRACK DIAGNOSIS
Some cracks are cosmetic. Some are warnings. Some are structural emergencies. Here is how to tell which you have — and what each type actually means.
Every year after the major rains, homeowners across Ghana notice new cracks on their walls, ceilings, or floors that weren’t there before. Some are hairline fractures barely visible under paint. Some are visibly open, going all the way through the plaster. Some are wide enough to fit a coin.
What do they all mean? The honest answer: it depends on where the crack is, how wide it is, and what direction it runs. Here is how to read what your walls are telling you.
The Five Types of Cracks and What Each One Means
1. Hairline Cracks in Paint or Plaster (Cosmetic)
Width: Less than 0.5 mm — you can barely see them without close inspection
Direction: Any direction, often random spider-web patterns
What they mean: Normal shrinkage of paint or plaster as it ages, especially after wet-season humidity fluctuations. These are cosmetic.
Action: Ignore, or repaint at your next scheduled refresh. Not urgent.
2. Vertical or Diagonal Cracks Through Plaster (Movement)
Width: 0.5–2 mm
Direction: Vertical, or diagonal from corners of doors and windows
What they mean: Building movement. Concrete slabs and blockwork expand and contract as they heat, cool, and take up/release moisture. Cracks appear at the weakest point, which is usually the plaster over a junction between different materials (e.g., blockwork meeting concrete, or above a door/window lintel).
Action: Not immediately structural, but crack repair is warranted — chase, fill with flexible crack filler, repaint. If cracks keep re-opening, the movement is ongoing and a more substantial repair is needed.
3. Horizontal Cracks in Plaster or Blockwork (Warning)
Width: 1–5 mm
Direction: Horizontal, running along the wall
What they mean: Often indicates one of two things:
- Rising damp reaching a specific mortar course, weakening it
- Lateral pressure on the wall (from expansive soil, poor drainage against the wall, or roof pressure)
Action: Investigate. Horizontal cracks are more concerning than vertical ones. Get a specialist to inspect before deciding on the fix.
4. Stepped / Zigzag Cracks Through Blockwork (Serious)
Width: 2–5 mm+
Direction: Stepping through the mortar joints between blocks in a diagonal or zigzag pattern
What they mean: Foundation settlement or subsidence. One part of the foundation has moved relative to another, and the wall is cracking to accommodate the movement.
Action: This is structural. Get a structural engineer’s assessment before doing any cosmetic repair. Foundation stabilisation may be needed before waterproofing.
5. Wide Cracks With Displacement (Structural Emergency)
Width: 5 mm+ with visible offset between the two sides of the crack
Direction: Any
What they mean: Serious structural movement. Something in the foundation or load-bearing system has failed or is failing.
Action: Call a structural engineer immediately. Do not attempt cosmetic repair. Do not ignore.
The Water Connection
Almost all wall cracks that appear or worsen during and after the rainy season have a water component. Water:
- Weakens the soil under your foundation, allowing settlement
- Corrodes reinforcement steel inside concrete elements, causing the steel to expand and split the concrete from within
- Saturates blockwork and mortar, allowing movement that wouldn’t happen dry
- Freezes and expands (rare in Ghana but possible in higher altitudes) in existing hairline cracks
- Drives cyclical wet-dry expansion of clay soils that push against foundation walls
This is why waterproofing your building envelope is preventive maintenance for the structure itself — not just for cosmetic finishes.
How to Monitor a Suspicious Crack
If you’re unsure whether a crack is stable or growing, do this simple test:
- Take a photo of the crack next to a ruler or coin for scale
- Mark the crack ends with pencil
- Write the date next to the mark
- Repeat monthly for 6 months
If the crack has not moved beyond your pencil marks in 6 months, it’s stable. If it grows, it’s active — call a professional immediately.
Repair Approach by Crack Type
| CRACK TYPE | REPAIR APPROACH | TYPICAL COST |
| Hairline / cosmetic | Fill + repaint | GHS 500 – 2,000 |
| Movement cracks (1–2 mm) | Chase + flexible filler + repaint | GHS 2,000 – 6,000 |
| Horizontal cracks (1–5 mm) | Investigate cause + treat + finish | GHS 5,000 – 25,000 |
| Stepped / structural | Structural engineer + foundation work | GHS 30,000 – 200,000+ |
| Wide with displacement | Structural emergency | Site-specific |
Get a Free Crack Diagnosis
We can assess whether the crack is cosmetic, moisture-related, or structural. For structural cracks, we work with independent structural engineers.
- Phone: 0555 548 001 or 0241 737 026
- WhatsApp: Send us photos with a ruler for scale
- Related: Foundation Waterproofing · Efflorescence
Festghana Waterproofing Solution Company Limited provides crack diagnosis, waterproofing repair, and moisture control services across Ghana. Workmanship warranty on every job.