Concrete vs Block Paving

What Concrete and Block Paving Actually Are

A concrete driveway is a rigid pavement system. It is formed by pouring a cementitious slab over a prepared sub-base, typically reinforced with steel mesh or fibres. Once cured, it behaves as a single continuous plate.

Block paving is a segmented surface system. Individual units are laid on a bedding layer and restrained laterally by edge restraints. Structurally, it behaves as an interlocking lattice that distributes load between neighbouring blocks.

The surface layer in both systems contributes very little structural strength. The true load-bearing capacity comes from the foundation beneath. The surface mainly controls how movement becomes visible and how failures express themselves over time.

Context: Block Paving vs Porcelain for Driveways • Can You Re-Bed Driveway Blocks? • Permeable Block Paving Explained

How Each System Carries Load

Concrete load behaviour

Concrete behaves as a rigid plate. Wheel loads are spread across the slab thickness and then transferred into the sub-base below.

This rigidity reduces surface deflection but increases sensitivity to differential settlement. Any local loss of support beneath the slab creates bending stresses that concrete cannot tolerate.

Block paving load behaviour

Block paving behaves as a flexible load-sharing grid. Loads are transferred into the bedding layer and laterally into adjacent blocks.

This allows the system to tolerate small local settlements without catastrophic failure. The surface deforms rather than cracking, which makes structural problems visible earlier but less destructive.

Foundation Depth Differences

Concrete does not allow thinner foundations. In fact, it often requires thicker and stiffer sub-bases than block paving to control slab bending stresses.

Typical sub-base ranges (competent ground)

• Light cars only: 150–200 mm
• Cars + vans: 200–250 mm
• Frequent commercial vehicles: 250–350 mm

Concrete also requires a minimum slab thickness to control cracking and edge failure. Domestic driveways typically use:

• Light cars only: 100–125 mm concrete
• Cars + vans: 125–150 mm concrete
• Commercial loads: 150–200 mm concrete

Thin concrete slabs over weak sub-bases fail faster than flexible paving systems.

How Each Handles Ground Movement

Concrete and movement

Concrete does not tolerate differential movement. Any uneven settlement beneath the slab creates tensile stresses that exceed concrete’s low tensile strength.

Cracks are not a defect. They are a predictable structural response to bending stress.

Block paving and movement

Block paving accommodates movement by re-leveling itself locally. Blocks can rotate slightly, bedding sand can compress, and joints can absorb micro-movements.

This prevents catastrophic cracking, but it does not eliminate the need for foundation strength. Excessive movement still leads to surface deformation.

Context: Clay Soil and Driveways • Ground Movement and Driveways • Ground Movement and Patios

Drainage Behaviour and Water Sensitivity

Concrete drainage behaviour

Standard concrete is impermeable. All water must be directed off the surface or intercepted by drainage channels.

Trapped water beneath concrete softens the sub-base, increases slab bending, and accelerates cracking and edge failure.

Block paving drainage behaviour

Block paving is semi-permeable at the joints. Water can infiltrate into the bedding layer and then into the sub-base.

This reduces surface runoff but increases the importance of a free-draining foundation design. Poor drainage beneath blocks leads to pumping, joint loss, and long-term settlement.

Context: How Much Fall Does a Patio Need? • Patio Drainage Basics • What Are Surface Falls?

Maintenance and Repair Reality

Concrete maintenance

Concrete requires sealing to limit water ingress and staining. Oil contamination permanently discolours it.

Local repairs are always visible. Colour matching and texture blending are almost impossible. Structural cracks cannot be made to disappear.

Block paving maintenance

Block paving requires periodic joint sand replenishment. Weed growth is cosmetic, not structural.

Local repairs are invisible when done correctly. Individual blocks can be replaced indefinitely. The surface can be lifted and relevelled decades later.

Common Failure Modes

Typical concrete failures

• Random cracking from slab bending.
• Edge collapse from poor restraint.
• Surface scaling from freeze–thaw damage.
• Spalling around joints and corners.

Typical block paving failures

• Local settlement and rocking blocks.
• Joint sand loss and surface loosening.
• Edge creep from weak restraints.
• Bedding layer washout.

In both systems, almost all failures trace back to: insufficient sub-base depth, poor drainage, weak edge restraint, or bad compaction.

Context: Signs Your Driveway Was Built Wrong • Can You Re-Bed Driveway Blocks? • Driveway Build-Up Explained

Correct Design Rules

• Design the foundation before choosing the surface.
• Scale sub-base depth to axle loads and soil strength.
• Provide mechanical edge restraint for both systems.
• Install drainage to keep the structure dry.
• Use control joints in concrete to manage cracking.
• Overbuild on clay and marginal ground.

Concrete should never be chosen for clients who expect invisible repairs or zero cracking. Block paving should never be chosen for clients who expect zero maintenance.

Related Guides

• Why Driveways Fail After Winter (Freeze–Thaw, Saturation, and Movement)
• Concrete Strength Grades Explained: C20, C25, C30 and What They Mean
• Patio Foundations Explained (What Supports the Build Long-Term)
• Permeable Block Paving Explained (How It Works—and How It Fails)
• Driveway Ventilation Rules (Air Bricks, Damp Risk, and Levels Against Walls)