What is Underpinning and why

What Is Underpinning – And Why Is It Necessary?

Ground movement is one of those quiet forces that can slowly undermine the stability of a building. Most property owners don’t realise anything is going on until the cracks show up—or in some cases, doors stop closing properly, floors feel a bit off, or an extension starts drifting slightly away from the main house.

That’s usually the point where underpinning comes into the picture.

Underpinning is basically the process of adding strength, stability, or extra load-bearing capacity to the existing foundations. Traditionally that meant digging underneath a building and pouring lots of concrete. More modern methods (like geopolymer injection) can do the same thing without all the mess and noise.

Why Is Underpinning Necessary?

Buildings need underpinning for a handful of reasons. Here are the main ones:

1. The ground has weakened or moved

Soils aren’t static. Clay shrinks in hot, dry summers and swells after heavy rain. Loose fill can settle unevenly. Trees can draw out moisture and create pockets of weakness.
When the soil can’t support the structure anymore, the building starts to settle—and underpinning restores that support.

2. The building has subsidence

Subsidence is downward movement because the ground has lost bearing capacity.
Left alone, it almost never sorts itself out. Underpinning stops the movement, stabilises the property, and prevents things getting worse.

3. The building’s load has changed

Adding an extension? Converting a loft? Using the building differently?
Sometimes the original foundations simply weren’t designed for the extra weight, so underpinning makes sure everything can cope.

4. The original foundation wasn’t great to begin with

Older homes often sit on shallow or outdated foundations. Over the years these can degrade or become inadequate compared to today’s standards.
Underpinning strengthens and updates them without needing to rebuild the entire structure.

5. The adjacent ground has been disturbed

Construction work next door, deep excavations, new basements or tunnelling can all unsettle nearby ground.
Underpinning helps protect your property from changes happening outside your control.

Traditional vs Modern Underpinning Approaches

Traditional Concrete Underpinning

This involves digging trenches under the foundations and filling them with concrete.
Pros: Strong, well understood, has been used for decades.
Cons: Slow, disruptive, messy, involves a lot of excavation, and can temporarily destabilise the building while work is going on.

Geobear resin injection underpinning (Modern alternative to underpinning)

This is the method Geobear uses. A specialist geopolymer resin is injected into the ground where it expands, fills voids, compacts the soil, and can even lift the structure if needed.
Pros:

• No excavation
  
  
• Minimal disruption
  
  
• Very fast (often done in a day)
  
  
• Cost-effective
  
  
• Environmentally friendlier
  
  
• Works immediately
  
  

Cons: Needs specialist expertise and a correct diagnosis—definitely not a DIY job.

How to Know If Your Property Needs Underpinning

Look out for signs like:

• Cracks wider than 3mm, especially diagonal ones
  
  
• Floors that aren’t level
  
  
• Windows or doors sticking for no obvious reason
  
  
• Gaps between floors and skirting boards
  
  
• An extension pulling away from the main building
  
  
• Wallpaper wrinkling or rippling (when there's no damp issue)
  
  

Any of these might be symptoms of ground movement. The earlier you get it checked, the easier—and usually cheaper—it is to put right.

Final Thoughts

Underpinning is ultimately about protecting the long-term safety, value, and structural health of your home. Whether the problem is subsidence, weakened ground, or changes to the building itself, underpinning is what restores the stability the property relies on.

And today, with modern methods like Geobear’s geopolymer injection, underpinning doesn’t have to mean weeks of digging and disruption. In many cases it’s precise, fast and surprisingly clean—often with very little impact on day-to-day life.