Resin Injection vs Traditional Underpinning: An Honest Comparison for Norfolk Properties

If your property has subsidence, you'll likely be offered one of two main repair methods: geopolymer resin injection or traditional mass concrete underpinning. Both work — but they suit different situations. This guide explains the real differences so you can have an informed conversation with your engineer or insurer.

How Each Method Works

Traditional Underpinning

Sections of earth are excavated beneath the existing foundation in sequence — typically in 1-metre bays — and filled with concrete to create a new, deeper footing. This extends the foundation down to stable ground below the zone affected by clay shrinkage or root activity.

Resin Injection

A two-part geopolymer resin is injected through 16mm holes drilled through the floor slab or external ground. The resin expands underground, filling voids, compacting loose soil, and — where needed — lifting settled structures back towards level. The whole process is monitored in real time using laser levels.

Side-by-Side Comparison

When Resin Injection Is the Better Choice

Resin injection works best when the ground movement is moderate (up to around 25mm of settlement), the cause has been addressed (e.g. a tree removed or pruned), and the soil conditions allow the resin to expand and compact effectively. It's particularly well-suited to Norfolk's boulder clay soils because the resin fills the shrinkage cracks within the clay itself.

It's also the preferred option for occupied properties, period properties where excavation would cause damage, and commercial buildings where downtime must be minimised.

When Underpinning Is Necessary

Traditional underpinning is the right approach when:

• • Movement is severe or ongoing and the foundation needs to bypass the problem ground entirely
• • The bearing stratum is very deep (more than 4 metres below ground level)
• • The property has already been underpinned on one side and needs matching on another
• • A structural engineer specifies it due to the nature of the loading or ground conditions

In Norfolk, underpinning is more commonly needed in King's Lynn and Downham Market where soft fen deposits extend to considerable depth, and in parts of Great Yarmouth where marine alluvium provides poor bearing capacity.

Can You Combine Both Methods?

Yes — and we frequently do. A property might need traditional underpinning on the most severely affected corner, with resin injection used to stabilise and re-level the remaining foundations. This hybrid approach often delivers the best outcome at a lower overall cost.

Questions to Ask Your Engineer

• • What is the soil type beneath my foundations? (This determines which method will work.)
• • Has the cause of movement been identified and addressed?
• • What warranty comes with the repair?
• • Will the repair be accepted by my insurer and future buyers' surveyors?

The right repair method depends on your ground conditions, not on which technique a contractor prefers. Always ask for a site-specific recommendation based on survey data.