Experts in Concrete Patio installation

Fixing an Uneven Concrete Patio: Options for UK Gardens

A concrete patio should feel solid and level underfoot. If yours has started to slope, sink, or wobble, it's likely more than just a cosmetic issue. Uneven patios are not only unsightly but can create safety risks and drainage problems. Understanding what’s causing the movement is the first step toward fixing it correctly and ensuring it doesn’t happen again.

This guide outlines the most common causes of uneven patios in the UK and explores your best options for levelling them, whether you’re looking for a simple lift or a full structural rebuild.

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Why Concrete Patios Become Uneven

Uneven patios are common in the UK due to changing weather, unstable ground, and ageing foundations. Whether the slab has sunk, cracked, or lifted, the root cause often lies beneath the surface. Understanding what’s going on underneath will guide your repair options and help prevent repeat issues.

Poor Ground Preparation

Many uneven patios are the result of shortcuts taken during the initial installation. If the ground wasn’t excavated to the correct depth or compacted properly, it can shift over time. A weak sub-base allows the concrete above to move, leading to visible dips or high points. This is especially common in DIY patios or those built without a proper layer of MOT Type 1 or crushed stone beneath the slab.

Soil Movement and Settling

British gardens often sit on clay-heavy or moisture-sensitive soils. After heavy rainfall or drought, the ground can expand or contract, causing movement underneath concrete slabs. This uneven pressure can make parts of the patio sink or rise. Over time, these shifts become visible and may also lead to cracking if left untreated.

Water Drainage Issues

Poor drainage is a major factor in patio movement. When water is allowed to sit under or around a slab, it weakens the supporting soil. If the patio was installed without a proper fall (slope) or lacks soakaways or drains, it can collect rainwater. This pooled water saturates the ground and undermines the base, causing unevenness.

Tree Roots and Garden Obstructions

Large trees, hedges, or shrubs planted near a patio can affect its stability. Tree roots can lift slabs, while decaying roots may leave hollow pockets underneath, causing collapse. If plants are too close to the patio edge, they can also trap moisture and contribute to movement or heaving along the perimeter.

General Age and Wear

Like all outdoor features, patios degrade over time. Years of foot traffic, frost, and temperature changes cause minor shifts that gradually build into noticeable unevenness. If your patio is more than 10–15 years old, uneven surfaces may simply be the result of natural wear, especially if it wasn’t sealed or maintained regularly.

Options for Fixing an Uneven Patio

Resin or Foam Injection (Slab Lifting)

A fast and less invasive method for lifting sunken slabs without removing them.
Resin or foam is injected beneath the slab, expanding to fill voids and lift the concrete back into place.
Works best for minor-to-moderate sinking caused by poor base or soil settling.

Re-laying Individual Slabs

If only one or two slabs have dipped, they can be carefully removed and reinstalled on a fresh, compacted sub-base.
Good for isolated movement or where the rest of the patio is still structurally sound.
Cost-effective and relatively quick compared to full replacement.

Full Patio Replacement

Recommended if the patio has widespread unevenness, poor drainage, or is breaking apart.
Allows for correction of base layers, redesign of layout, and installation of proper drainage systems.
Long-term solution with the chance to upgrade design, finish, and durability.

Frequently Asked Questions

Common causes include poor sub-base preparation, changes in soil moisture, tree root growth, and water pooling underneath the patio. Over time, these issues can make a concrete slab lose its level foundation.

In some cases, yes. Small sections that have dipped slightly can sometimes be lifted and reset on a better sub-base. However, more severe issues like slab sinking or structural cracks typically require professional tools and knowledge.

Slab lifting is effective and durable when done correctly, especially if the underlying soil is stable. That said, if the root issue isn’t addressed (e.g. drainage or base problems), the slab may shift again over time.

If more than 30–40% of the patio is uneven, or the sub-base has failed, a full replacement is usually the most cost-effective long-term option. It also gives the opportunity to fix layout and drainage issues during installation.

Start with proper ground prep and a strong, compacted sub-base. Include drainage channels or soakaways, and avoid planting trees too close. Sealing your concrete and checking for movement early can also reduce long-term problems.