Subsidence Cracks in Wall and When You Should Worry

Cracks in walls can be concerning for homeowners. While some cracks are harmless, others may signal serious structural issues like subsidence.

Subsidence cracks are often wide, diagonal, and appear around doors and windows.

These cracks form when the ground beneath a building shifts or sinks. Many factors can cause this, such as nearby trees drawing moisture from the soil or leaking pipes washing away the earth under your home.

Spotting subsidence early is key to preventing costly damage.

Not all cracks mean your home is sinking. Normal settlement in new builds can cause small cracks in the first 10 years. Thin, vertical cracks are often harmless and easy to fix. But if you see wide cracks that grow over time, it’s best to get them checked by a pro.

Key Takeaways

  • Wide, diagonal cracks around doors and windows may signal subsidence
  • Early detection of subsidence can save you from expensive repairs
  • A professional should assess any cracks you’re worried about

Understanding Subsidence

Subsidence occurs when the ground beneath a building sinks, causing structural problems. It can lead to serious damage if left unchecked.

Causes of Subsidence

Several factors can trigger subsidence. Clay soil is a common culprit, as it shrinks and swells with changes in moisture. This movement can destabilise foundations.

Tree roots near buildings are another issue. They absorb water from the soil, causing it to dry out and shrink. Large trees can be especially problematic.

Leaking drains or pipes can wash away soil particles, creating voids under foundations. This erosion weakens the ground’s ability to support structures.

Mining areas face unique risks. Old mine shafts or tunnels can collapse, leading to sudden ground movement.

Signs and Symptoms

Cracks in walls are a key indicator of subsidence. These often appear suddenly and are wider at the top than the bottom. They tend to be diagonal and wider than 3mm.

Doors and windows may stick or not close properly. This happens as the building’s frame shifts.

Rippling wallpaper can be a subtle sign, especially if there are no issues with damp.

Sinking floors might develop. Look for uneven surfaces or gaps around skirting boards.

External signs include cracks in brickwork or gaps where extensions join the main building.

Types of Cracks

Cracks in walls can vary in size and severity. Some are minor cosmetic issues, while others point to serious structural problems.

Hairline Cracks

Hairline cracks are thin, superficial lines that appear on walls. They’re often less than 1mm wide and don’t usually mean there’s a big problem.

These cracks can form due to:

  • Paint drying
  • Plaster settling
  • Small shifts in the building

You might spot hairline cracks:

  • Around windows and doors
  • Where walls meet ceilings
  • In the corners of rooms

Most hairline cracks don’t need fixing. But keep an eye on them. If they get bigger, it could be a sign of a bigger issue.

Structural Cracks

Structural cracks are wider and deeper than hairline cracks. They can be a sign of serious problems like subsidence.

Look out for:

  • Cracks wider than 5mm
  • Cracks that go through bricks, not just mortar
  • Cracks in a stair-step pattern

These cracks often show up:

  • Near foundations
  • Around load-bearing walls
  • At weak points in the structure

Structural cracks need expert help. Don’t try to fix them yourself. A building surveyor can check the problem and suggest fixes.

Diagnosing Subsidence Cracks

Spotting subsidence cracks early can save you from costly repairs. Here’s how to identify these telltale signs of structural issues in your home.

Professional Assessment

A structural engineer is best equipped to diagnose subsidence cracks. They will:

  • Examine crack patterns and widths
  • Check for door and window misalignment
  • Use specialised tools to measure movement
  • Assess the building’s foundation

The expert may also:

  • Review local soil conditions
  • Look at nearby trees and vegetation
  • Check for leaking pipes or drainage issues

Their report will detail the severity of the problem and suggest next steps. This might include monitoring the cracks over time or recommending immediate action.

Self-Inspection Tips

While waiting for a professional, you can look for these signs:

  • Wide, diagonal cracks, especially near doors and windows
  • Cracks wider at the top than the bottom
  • Rippling wallpaper with no obvious cause
  • Sticking doors or windows

Pay attention to:

  • When cracks appeared
  • If they’re growing or changing
  • Any nearby trees or changes in soil moisture

Take photos and measurements of suspicious cracks. This information will be helpful for the expert assessment. Remember, not all cracks mean subsidence, but it’s better to be cautious.

Repair Techniques

Fixing subsidence cracks in walls requires both short-term and long-term solutions. These techniques range from simple DIY methods to more complex professional repairs.

Temporary Fixes

For small cracks, you can use simple DIY methods as a short-term fix. One option is to fill the crack with flexible filler or caulk. This helps prevent moisture from entering and causing further damage.

Another method is crack stitching. This involves drilling small holes on either side of the crack and inserting metal bars to hold the wall together. You can then cover the repair with plaster.

For larger cracks, you might need to use expanding foam. This fills the gap and provides some insulation. Remember, these are only temporary solutions and won’t address the underlying issue.

Long-Term Solutions

For permanent repairs, you’ll need to tackle the root cause of the subsidence. This often involves underpinning the foundation. Professionals will dig beneath the existing foundation and pour new concrete to stabilise the structure.

Another option is resin injection. This method pumps a special resin into the ground beneath the foundation. The resin expands, filling voids and strengthening the soil.

In some cases, you might need to address drainage issues. Improving drainage around your property can help prevent future subsidence problems.

For severe cases, you may need to rebuild part of the wall. This is a major job that requires professional help. Always consult a structural engineer before undertaking any major repairs.

Prevention and Maintenance

Taking steps to prevent subsidence and maintain your property can save you from costly repairs. Regular upkeep and monitoring are key to avoiding serious issues.

Soil Management

Proper soil management is crucial for preventing subsidence cracks.

Keep the soil around your house at a consistent moisture level. Water your garden during dry spells, but don’t overdo it.

Install proper drainage to direct water away from your home’s foundation.

Plant trees at a safe distance from your house. As a rule of thumb, the distance should be equal to the tree’s expected mature height. For existing trees near your home, consider pruning or removing them if they’re too close.

Fix any leaking pipes or drains quickly. Water from leaks can wash away soil, leading to instability. Check gutters and downpipes regularly to ensure they’re not blocked or damaged.

Regular Monitoring

Keep an eye out for early signs of subsidence.

Look for diagonal cracks wider than 3mm, especially near doors and windows. These cracks are often wider at the top than the bottom.

Check your floors for unevenness or sloping.

Doors and windows that stick or don’t close properly can be early signs of structural movement.

Inspect external walls for new or widening cracks.

Pay extra attention after long dry spells or heavy rain.

Consider getting a professional survey every few years, especially if your home is in an area prone to subsidence.

Experts can spot issues you might miss and provide advice on preventive measures.