One of the most common questions homeowners ask is: “Is this crack getting bigger?” It’s a sensible concern because a stable crack is rarely a problem, but a growing one deserves attention. This guide will help you spot the warning signs that a crack is actively worsening.
Why Growth Matters
A crack that’s been the same size for three years is probably just a cosmetic issue. A crack that’s visibly wider this month than it was last month is telling you something is happening in your building. Growth indicates active movement or deterioration, which means action might be needed.
The key skill is learning to monitor your cracks properly so you can spot real growth versus imagined growth.
How to Spot Growth
Visual Changes You Might Notice
- It looks wider: This is the most obvious sign. If you can see more space between the edges of the crack than there was before, it’s widening. The trouble is, our eyes can be deceiving. Shadows, lighting, and angle make cracks look different at different times of day.
- It’s getting longer: Has the crack extended further down the wall, or started branching off in new directions? A crack that was 30cm long last month but is now 50cm is definitely growing.
- It’s spreading horizontally: Watch for horizontal extensions from a vertical crack. This can indicate lateral pressure or movement spreading through the wall.
- New cracks are appearing nearby: If you spot fresh cracks appearing close to the original one, especially following similar patterns, it suggests the underlying cause is ongoing rather than a one-off event.
- The edges are becoming rougher: As a crack grows, the edges often become more ragged and damaged. The plaster around it might start to crumble or flake away. This usually indicates active movement.
Physical Sensations
- You can feel the step getting bigger: If the crack has displacement (one side higher than the other), and this offset is becoming more pronounced, that’s a clear sign of worsening movement.
- Dust is accumulating in the crack: Fresh dust or debris inside a crack suggests it’s actively moving and creating friction between the edges. This is a sign of ongoing movement.
- The crack feels softer or more crumbly: If the edges of the crack are becoming friable or crumbling more easily, it indicates deterioration is happening.
Practical Monitoring Methods
The best way to track growth is through systematic monitoring. Pick a method and stick with it.
Method 1: The Ruler Photograph
This is the most reliable method for most homeowners.
- Position a ruler vertically beside the crack
- Take a clear photograph with good lighting, ensuring the ruler is visible
- Write the date on the back of the photo or in your phone’s notes
- Repeat the process monthly, trying to use the same angle and lighting
- Compare photos side by side to spot any widening
You can be very precise with this method. If the crack was 4mm wide in January and 5mm wide in March, you have proof it’s growing.
Method 2: The Tape Mark
For cracks you want to monitor closely:
- Apply a strip of masking tape or painter’s tape across the crack
- Use a permanent marker to draw lines on the tape that align exactly with the crack edges
- Mark the date on the tape
- Check the tape monthly to see if the crack edges have moved beyond your marks
If the crack has grown, it will have shifted beyond your marked lines.
Method 3: The Witness Mark
For very fine cracks:
- Use a small piece of clear tape and mark the extent of the crack with a permanent marker
- Photograph it alongside a ruler
- Repeat monthly
Method 4: The Phone App
Several smartphone apps can help you monitor cracks over time by marking measurements and storing timestamped photos. Search for “crack monitoring app” in your app store.
Timeline: What Different Growth Rates Mean
| Growth Pattern | Timeframe | What It Suggests | Action |
|---|---|---|---|
| No visible change | 6+ months | Stable, likely cosmetic | Monitor but low concern |
| Minimal growth | 1-2mm over 6 months | Slow, gradual movement | Continue monitoring |
| Steady growth | Visible widening over 2-3 months | Ongoing building movement | Get professional assessment soon |
| Rapid growth | Noticeably wider in weeks | Active structural issue | Seek professional advice quickly |
| Sudden appearance of new cracks | Multiple in short time | Significant movement occurring | Professional assessment needed |
Other Changes to Track
Beyond just measuring the crack itself, watch for these additional changes:
Associated Damage Worsening
- Doors or windows sticking more than before
- Paint cracking or peeling more extensively
- Plaster crumbling more noticeably around the crack
- Damp patches spreading or getting worse
New Problems Appearing
- Fresh cracks appearing elsewhere in the property
- Skirting boards or cornicing pulling away from walls
- Tiles cracking or becoming loose
- Wallpaper bubbling or peeling more than usual
Seasonal Patterns
Keep track of when changes occur. If the crack widens in summer and narrows slightly in winter, that suggests thermal movement (which is usually harmless). If it grows regardless of season, something else is happening.
Red Flag Combinations
Individual warning signs are worth watching, but certain combinations are more concerning and warrant faster action.
| Combination | Concern Level | Why | Action |
|---|---|---|---|
| Growing crack + damp nearby | Very High | Suggests ongoing structural and moisture issues | Contact professional soon |
| Growing crack + sticking doors | Very High | Indicates active building movement affecting structure | Professional assessment needed |
| Rapid growth + multiple new cracks | Very High | Suggests significant structural movement | Seek advice quickly |
| Growing horizontal crack + displacement | Very High | Can indicate subsidence or serious movement | Priority professional assessment |
| Stable crack + no other issues | Low | Normal cosmetic damage | Monitor, fix cosmetically when ready |
| Slow growth over years + no other issues | Low to Medium | Gradual settling or movement | Monitor, professional assessment optional |
Common False Alarms
Not every apparent change means your crack is growing. Here are things that might fool you:
Lighting Changes
A crack looks much more prominent in bright sunlight than in dim indoor lighting. This doesn’t mean it’s grown, just that you’re seeing it differently.
Wet Versus Dry
Cracks often look wider when the wall is wet or damp because the moisture fills the space. The same crack will look narrower when dry.
Angle and Perspective
Photographing a crack from slightly different angles will make it appear different sizes. Try to photograph from the same spot each time.
Seasonal Paint Flaking
As paint around a crack deteriorates naturally with age, it might look like the crack has grown when actually the paint is just failing.
New Paint or Plaster
If someone has recently painted or plastered around the crack, the new finish makes the old crack look more dramatic by comparison.
When to Act on Growth
You should seek professional advice if:
- The crack has visibly widened by 1-2mm or more over a period of months
- The crack is growing in length noticeably (extending further along the wall)
- You’ve measured it multiple times and confirmed it’s genuinely getting bigger
- Multiple new cracks are appearing at the same time
- The crack is associated with other problems like sticking doors or damp
- The growth is rapid (noticeable change in weeks rather than months)
What a Professional Will Look For
When you contact a surveyor or structural engineer, they’ll be checking:
- The rate and pattern of growth
- Whether it’s a new problem or long-standing
- Whether growth is seasonal or consistent year-round
- Associated signs of building movement
- The underlying cause
- Whether immediate action is needed or monitoring is sufficient
Tips for Accurate Monitoring
- Be consistent. Check monthly rather than sporadically.
- Use the same method each time you check.
- Keep records. A photo from three months ago is more reliable than your memory.
- Don’t panic at first signs of growth. Measure and track for at least two to three months to confirm a pattern.
- Share your records with a professional. They’ll appreciate having concrete data.
- Remember that very slow growth over years is different from sudden rapid growth.