Experts in Concrete Patio installation

The Right Base for a Long-Lasting Concrete Patio

Most concrete patio problems begin below the surface. Without a properly prepared base, even the best concrete will crack, sink, or shift over time. A solid foundation is essential to creating a long-lasting patio, especially in the UK where moisture and soil movement are common challenges.

This guide explains the importance of sub-base preparation, what materials to use, and how to build a concrete patio that stays strong and level for decades.

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Why the Base Matters More Than the Surface

A concrete patio is only as strong as what lies beneath. These are the core reasons why a properly installed base is the best way to avoid cracks, sinking, and expensive repairs.

Prevents Cracking from Soil Movement

In many parts of the UK, soil expands when wet and contracts when dry. Without a stable base, this natural ground movement puts stress on the concrete slab. Over time, that stress leads to surface and structural cracks. A well-compacted sub-base absorbs and distributes movement, helping your patio remain intact through seasonal changes.

Improves Drainage and Reduces Frost Damage

A quality base layer allows water to drain away from the slab, reducing the chance of pooling and frost damage. Standing water beneath the concrete can freeze and expand during winter, lifting or cracking the slab. Installing a permeable sub-base and compacting it correctly ensures moisture moves downward rather than collecting under your patio.

Supports Heavy Loads

If your patio will hold furniture, planters, hot tubs, or even light vehicles, the sub-base must be designed to take the weight. Without adequate support, the slab can sink or fracture under pressure. A properly laid MOT Type 1 base with the right thickness ensures the patio stays level and strong even under demanding loads.

Extends Patio Lifespan

A poor base might not cause immediate failure, but it almost always leads to issues within a few years. Investing time in proper base construction drastically extends the life of your patio, saving you money and hassle in the long run. It also prevents unsightly settling or joint separation.

Complies with UK Industry Standards

In professional UK landscaping and building, a correctly prepared sub-base is essential for compliance. Using industry-recommended materials and compaction methods means your patio won’t just look good, it’ll meet long-term performance standards and avoid structural failure.

Building the Right Patio Base in the UK

Excavate to the Right Depth

Remove all topsoil and soft ground to a minimum depth of 150–200mm.
Make sure the ground is flat and graded slightly away from buildings for drainage.
Mark out any cable or pipe runs to avoid disruption during future work.

Lay and Compact MOT Type 1

Use 100–150mm of MOT Type 1 sub-base material, which includes crushed stone of various sizes.
Compact in layers using a vibrating plate compactor to remove air gaps and improve stability.
A well-compacted base prevents future settling and keeps the slab evenly supported.

Install a Blinding Layer

Apply 25–50mm of sharp sand or lean concrete as a “blinding” layer on top of the base.
This helps level the surface, reduces friction, and allows the concrete slab to be poured evenly.
In some cases, a damp-proof membrane may also be laid to protect against rising moisture.

Frequently Asked Questions

MOT Type 1 is the standard base material for concrete patios in the UK. It’s made of crushed stone and provides excellent load-bearing support when compacted properly.

Most patios require a base depth of at least 150mm, including 100–150mm of sub-base and 25–50mm of blinding. Depth may vary depending on use and soil conditions.

Yes, compacting the base is essential. Loose or uneven base layers will settle over time, causing cracks and sinking. Each layer should be compacted before adding the next.

Pouring directly onto soil is not recommended. Soil shifts and absorbs moisture, which can lead to cracking and failure. A compacted sub-base is necessary for structural stability.

While no patio is immune to cracking, a proper base greatly reduces the risk. Combined with good drainage, joint placement, and sealing, it offers long-term protection and performance.