A Complete Guide to Laying Concrete

Sub-Base Essentials

What is a Sub-Base?

A sub-base is the compacted layer of material laid beneath a concrete slab, designed to support the load above and prevent movement or cracking. It distributes weight evenly and acts as a barrier against ground moisture and soil instability.

A stable, well-compacted sub-base is critical to avoid subsidence and cracks.

What Should You Use?

• MOT Type 1: Ideal for most structural slabs, driveways, and paths
• Sharp Sand/Gravel: Often used for non-structural slabs, patio bases, or under wet pours

Compaction Tips

• Use a wacker plate in 2–3 passes for every 50mm layer
• The sub-base should be at least 100mm thick for most applications
• Use a damp-proof membrane (DPM) over compacted base to block moisture ingress

Formwork & Reinforcement

What is Formwork and Shuttering?

Formwork, also known as shuttering, refers to the temporary moulds used to hold wet concrete in place until it hardens. It defines the shape, alignment, and surface finish of the finished slab or structure.

Setting the Shape

• Timber shutters are common, but make sure they’re straight, strong and well-secured
• Steel or plastic formwork is better for curved edges or reusable systems

When to Reinforce

• Steel mesh (A142 or A193) is often used for driveways, garages or poor ground
• Rebar cages are essential for slabs bearing heavy loads or on clay/silt

Expert Tip: “For successful groundwork and concrete pours, always appoint a reputable local groundworker with experience in the specific area. Their local knowledge can make all the difference to your project’s success.” – EKA Team

The Concrete Pour – Best Practices

Choosing the type of concrete delivery:

• Volumetric (site-mixed) concrete allows for on-site flexibility, ideal for changing needs and ensuring you only pay for what you actually use on the day.
• Ready mix is convenient for large, continuous pours but expect to pay part-load charges if you require less concrete than ordered

What is a Concrete Mix Design?

A concrete mix design is the specific combination of cement, aggregates, water, and additives tailored to meet the strength, durability, and workability requirements of a particular project. It ensures the concrete performs as expected under site conditions and loading demands.

Finishing & Curing

Surface Finishes

A surface finish refers to the final texture and appearance of a concrete slab once it has been placed and levelled. 

The type of finish chosen not only affects how the concrete looks but also how it performs, impacting things like slip resistance, durability, and suitability for different environments. Here are three of the most common finishing options:

• Brushed: Ideal for driveways and paths (slip resistance)
• Trowelled: Smooth indoor slabs or garage floors
• Exposed aggregate: Decorative, good for patios and footpaths

Proper Curing

Curing is critical for strength and durability:

• Cover with curing membrane or polythene immediately after finishing
• Keep above 5°C for 48+ hours (especially in winter)
• Use insulated blankets in cold weather or wet cure with hessian in hot weather
• Never build on the slab before 7 days, and wait 28 days for full strength

See official NHBC Standards and CIRIA Concrete Guidance for more curing advice.

Common Mistakes & How to Avoid Them

• Inadequate sub-base preparation often results in sinking slabs, surface cracking, or uneven finishes. Always compact the base in layers using appropriate equipment to provide a stable foundation.
• Overwatering the concrete mix can weaken the final product. While extra water might make placement easier, it dilutes the cement paste and leads to dusting, surface scaling, and poor durability.
• Failing to include expansion joints allows internal stress to build up and causes uncontrolled cracking. Always install control or expansion joints at recommended intervals to allow for movement.
• Overlooking ground conditions increases the risk of slab failure. Poor drainage, frost-prone areas, or sulfate-rich soils require mix design adjustments and specific preparation techniques.
• Pouring unreinforced slabs on clay or other unstable ground types can lead to significant movement over time. In such cases, reinforcement such as steel mesh or rebar is essential to prevent structural issues.

How to Choose a Supplier for Concrete Laying

Not all concrete is created equal. Look for:

Industry Standard Suppliers – The supplier consistently meets performance, safety, and material standards, and works hard to maintain them.

Volumetric Delivery – Mixing concrete on-site gives you maximum flexibility. You can adjust quantities and mixes as needed, and only pay for what you use – no waste, no over-ordering.

Friendly, Experienced Teams – A knowledgeable supplier can help solve real-world site challenges. Whether it’s a weather delay or challenging access, an experienced crew can adapt on the fly and keep your project moving forward.

Pump Hire and Site Mix Options – Having pump and site mix services available makes delivery faster, cleaner, and more precise, especially for complex pours or hard-to-reach areas.

Need help with the right mix or access solution? EKA Concrete offers concrete pumping services too.