Experts in Concrete Patio installation

Why Concrete Patios Sink Over Time and How to Raise Them

If parts of your concrete patio are uneven, sunken, or creating puddles where they shouldn’t, it’s likely your patio is settling or sinking, a problem seen often in UK gardens.

This guide explains what causes patios to sink over time, how to identify the early signs, and the best options available to lift and level the surface without tearing everything up.

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Why Concrete Patios Sink in the UK

Patio sinking happens when the support underneath a concrete slab shifts or weakens. In the UK, this is often due to ground conditions, poor preparation, or long-term moisture problems. Here’s a breakdown of the most common causes.

Poor Sub-Base Compaction

A concrete patio relies on a strong foundation to stay level. If the sub-base wasn't compacted properly during installation, or if soft soil was used instead of crushed stone, the ground can settle over time. This causes parts of the slab to sink, especially in high-traffic or waterlogged areas.

Heavy Rainfall and Drainage Issues

Excess water can erode the soil beneath a patio, especially if there’s poor drainage around the slab. In the UK’s wet climate, long periods of rainfall can wash away the base material, leaving voids that allow concrete to drop unevenly. Drainage planning is key during installation to prevent this.

Tree Roots and Vegetation

Nearby tree roots can shift or lift parts of the slab, but when roots die and decompose, they can also leave air pockets that cause sinking. Gardeners should take care when planting close to a patio edge and remove invasive roots that may be affecting the base layer.

Soil Type and Ground Movement

Clay-heavy soils, common in many parts of the UK, expand and contract dramatically with moisture changes. This natural ground movement can weaken the patio’s base and shift the slab above. Over years, these small changes create noticeable dips or uneven sections.

Age and Long-Term Wear

Over time, even the best patios will begin to show signs of settlement. Minor shifts in the sub-base, frost heave in winter, and decades of use all contribute to eventual sinking or tilting. Regular inspection can help catch problems early before they worsen.

How to Lift and Level a Sunken Patio

Slab Lifting with Foam Injection

This minimally invasive method involves injecting expanding polyurethane foam beneath the slab.
The foam fills voids and lifts the concrete back to level in a matter of hours.
It's clean, quick, and ideal for smaller or moderate dips without damaging the surrounding patio.

Resin Pressure Grouting

Grout or resin is pumped into the sub-base to stabilise and raise the slab.
This method is great for patios with wider or deeper subsidence and works well in moist soil.
The cured resin supports the slab long-term and helps reduce further sinking risk.

Full Removal and Reinstallation

If large areas have settled or cracked beyond repair, full replacement is the most reliable fix.
We lift and relay the patio with proper compaction, drainage, and reinforced concrete.
This ensures the patio is structurally sound and better protected from future movement.

Frequently Asked Questions

This is often due to poor sub-base compaction or erosion underneath that section of the slab. Water pooling or uneven ground movement can also contribute to one side settling faster than the other.

Yes, modern lifting methods like foam injection or resin grouting allow slabs to be levelled quickly without tearing them out. These are cost-effective for moderate subsidence and leave minimal disruption.

Minor sinking may not pose an immediate risk, but it can become a tripping hazard or worsen over time. Water pooling is also a concern. It's best to assess and repair early to avoid future problems.

When applied correctly, these methods can last many years. The foam or resin forms a durable support beneath the slab and resists further movement. Results vary depending on soil type and drainage conditions.

Yes, using a well-compacted MOT Type 1 sub-base, good drainage planning, and steel mesh reinforcement during installation greatly reduces the risk of future sinking or subsidence.