Clitheroe
Shap
Horwich, Bolton
Chorley
Horwich, Bolton
Clitheroe
Shap
Horwich, Bolton
Chorley
Horwich, Bolton
When it comes to outdoor construction, the quality of your groundwork can make or break the entire project. One of the most important but often overlooked elements is the sub base.
This essential layer sits beneath the surface materials like paving slabs, tarmac, or concrete, providing the foundation that keeps everything stable, level, and long-lasting.
Whether you’re laying a new patio, constructing a driveway, or preparing the ground for a road or path, the sub base plays a vital role in how well that surface performs over time. Without the right sub base aggregate, you risk movement, cracking, or even water pooling beneath your structure.
At Armstrongs, we supply a wide range of high-quality sub base materials, all quarried, graded, and tested to ensure consistency and compliance with construction standards. With decades of experience behind us, we’re proud to support builders, landscapers, and DIYers across the North West with durable, locally sourced aggregate solutions.
In this guide, we’ll explain what a sub base is, explore the different types of materials available, and offer practical advice on choosing the right depth and quantity for your project. You’ll also learn how to calculate your requirements, understand the differences between sub base layers, and get expert tips for a reliable installation.
A sub base is the layer of material installed directly beneath your chosen surface finish, whether that’s concrete, paving, or tarmac. It’s designed to bear the load of whatever is placed on top, from garden furniture to cars and heavy vehicles, and transfer that weight evenly across the ground.
This layer typically consists of crushed stone or sub base aggregate, which is compacted to create a solid, stable foundation. It acts as a bridge between the subgrade (the natural soil) and the upper layers of your build.
It’s important to note the difference between the subgrade and the sub base. The subgrade is the original soil that’s compacted before any materials are laid, while the sub base material is the man-made layer placed above it to ensure durability and strength.
The right sub base plays a crucial role in the success of any construction project. Firstly, it provides load-bearing support, helping to distribute weight and prevent settling or shifting that can cause uneven surfaces and cracking.
Secondly, a good sub base supports effective drainage, allowing water to pass through and away from your structure. Without this, you risk water buildup, which can damage both the surface material and the underlying soil.
Lastly, the compaction of your sub base is key. When properly compacted, it forms a stable layer that reduces movement over time, preventing surface failures and maintaining the integrity of your installation for years to come.
At Armstrongs, we help ensure your project starts with the right foundation. Our sub base materials are carefully selected and processed to provide maximum strength, reliability, and ease of compaction, whether you're building a patio, laying a driveway, or installing a new footpath.
Choosing the right sub base aggregate is essential for ensuring the long-term performance of your project. At Armstrongs, we supply a variety of sub base materials suitable for everything from small garden patios to large-scale infrastructure works. Below, we’ve broken down some of the most common types of sub base aggregate you’ll come across, and how to decide which is right for your job.
MOT Type 1 is one of the most widely used sub base materials in the UK. Made from crushed granite or limestone, this material contains particles of various sizes up to 40mm, including fines (very small particles). The presence of fines allows it to compact tightly, forming a solid, load-bearing surface once installed and rolled.
Because of its strength and compaction qualities, MOT Type 1 is the go-to choice for driveway sub bases, car parks, and access roads. It’s also approved for highway works, which speaks volumes about its durability.
We regularly supply MOT Type 1 from our quarries, ensuring it meets the standards needed for both domestic and commercial projects.
While similar to Type 1, MOT Type 2 and Type 3 have slightly different properties and are used in more specialist applications.
Type 2 still contains a mix of aggregates and fines but is usually less common in domestic work. It’s more often used in areas with weaker subgrades or where slightly more flexibility is needed in the base layer.
Type 3, on the other hand, contains little to no fines. This makes it more free-draining, which is particularly beneficial in projects where water management is a concern. It’s commonly specified in Sustainable Drainage Systems (SuDS), equestrian arenas, sports pitches, and other high-load environments where drainage is essential.
If your project demands strength and permeability, we recommend looking into Type 3 aggregate as a reliable solution.
Scalpings are a recycled sub base material, typically made from quarried stone that didn’t meet the exact grading for MOT Type 1. It’s still highly effective for many applications and represents a cost-effective and sustainable choice for those working to a budget.
You’ll often see scalpings used under patios, garden paths, or in light-duty landscaping where heavy traffic isn't expected. They compact well and provide a solid foundation, especially when sourced from quality stone like ours.
We produce scalpings from both limestone and gritstone at our quarries, ensuring excellent strength and consistency.
Granular Sub Base, often shortened to GSB, is a broader term for coarse aggregate layers used in larger infrastructure and civil engineering projects. Unlike MOT Type 1, GSB may contain larger stones and fewer fines, depending on the grade.
These materials are commonly laid beneath roads, motorways, or commercial developments where a thick, strong layer is needed to withstand substantial loads.
At Armstrongs, we supply GSB in a range of grades, tailored to meet your project’s specifications—whether you're building a public access road or preparing foundations for a large-scale commercial site.
When you’re preparing to lay a new patio, the sub base is just as important as the slabs you see on the surface. A well-laid sub base prevents movement, reduces the risk of cracking, and ensures a smooth, long-lasting finish.
For most patio installations, we recommend using MOT Type 1. It provides excellent compaction and durability, especially if your patio will experience regular foot traffic or support garden furniture.
For lighter-use areas or where budget is a key consideration, scalpings can be a cost-effective alternative. These still compact well and offer strong support when installed correctly.
Whatever material you choose, getting the depth right is essential. We generally advise laying your sub base for patios at a depth of around 100mm, ensuring it’s well compacted before moving on to the laying course.
Driveways take more stress than patios, so your choice of sub base material needs to handle the pressure—literally.
We typically recommend MOT Type 1 for most driveway sub base applications. Its well-graded particle sizes, from large stones to fine dust, allow it to compact into a dense, stable layer capable of withstanding vehicle loads.
If your site requires more effective water management, such as sloped ground or areas prone to standing water—you may want to consider MOT Type 3. It contains minimal fines, making it more permeable while still offering excellent structural support.
Regardless of the material, compacting your sub base thoroughly is critical. For driveways, we suggest a minimum compacted depth of 150mm. This creates a solid foundation that won’t shift, rut, or sink over time.
Knowing how much sub base to order is crucial for keeping your project moving and avoiding wasted materials or unexpected delays.
To calculate the required volume of sub base aggregate, simply use this formula:
Area (m²) x Depth (m) = Volume (m³)
For example, a 10m² patio with a 0.1m (100mm) sub base would require 1 cubic metre of material.
Keep in mind that compaction will reduce the final depth slightly, so we always recommend ordering a little extra to allow for settlement and coverage adjustments.
If you’re unsure how much sub base material you’ll need, especially for larger or more complex jobs—our team is happy to help. We can advise on volumes, delivery logistics, and recommend the right material based on your site conditions.
One of the most common questions we’re asked is: how much sub base do I need? Thankfully, it’s easy to calculate with a simple formula:
Area (m²) x Depth (m) = Volume (m³)
For example, if you’re preparing a 20m² driveway and need a 0.15m (150mm) layer of sub base, the calculation would be:
20m² x 0.15m = 3m³ of sub base aggregate
Remember to allow for compaction when placing your order—your final compacted depth will be slightly less than the loose depth when laid. It’s always better to round up to avoid running short during the job.
If you’re managing a larger-scale commercial or infrastructure project, our team at Armstrongs is on hand to help calculate accurate volumes and arrange bulk delivery of high-quality sub base aggregate direct from our quarries.
Getting your sub base material down correctly is vital for long-term strength and stability.
Start by excavating the area to your required depth, accounting for the sub base and final surface layers. You’ll want a clean, level surface to begin with, ideally, one that includes a weed control membrane if vegetation is a concern.
Next, lay your chosen sub base aggregate in layers no thicker than 75mm. Thicker layers won’t compact evenly, which can lead to future movement. Compact each layer using a vibrating plate compactor to achieve a solid, uniform base before moving on to the next.
If you’re laying a driveway or area with heavy loads, a well-compacted sub base will prevent sinking, rutting, or cracking over time.
We’ve seen it all over the years, and many surface failures come down to avoidable mistakes during the sub base stage.
One of the biggest is skimping on depth or choosing the wrong sub base material. For example, using fine fill instead of a properly graded aggregate like MOT Type 1 can leave you with a weak, unstable base.
Another major pitfall is failing to compact thoroughly. Without proper compaction, even the best material will shift under pressure, resulting in uneven paving or cracks appearing in the finished surface.
Taking the time to prepare and compact your sub base correctly can save you costly repairs or redos down the line. And if you’re unsure what you need, we’re here to advise.
At Armstrongs, we supply premium sub base aggregate that meets all relevant construction standards for grading, consistency, and compaction. Whether you’re working on a domestic patio or a large infrastructure scheme, you can rely on the quality of our materials to create a strong, stable foundation that lasts.
Because we quarry and process our sub base material right here in the North West, we also help reduce the carbon footprint associated with long-distance aggregate transport. Our local supply chain means less waiting, fewer delays, and more environmentally responsible sourcing.
We’re proud to support both trade professionals and members of the public — from weekend DIYers building a garden path to civil engineers managing large commercial sites.
Whatever the scale of your project, we’re here to help from initial enquiry through to delivery. Our knowledgeable team can help you choose the right sub base aggregate, calculate volumes, and ensure you receive the right product at the right time.
With Armstrongs, you get more than just materials, you get service, experience, and peace of mind.
For most patios, MOT Type 1 is the go-to choice due to its strength and compaction performance. However, scalpings can be a cost-effective alternative for lighter-use areas, particularly when laid and compacted properly.
For driveways, we generally recommend a compacted sub base of 100–150mm, depending on the weight of expected traffic. Always lay it in layers and compact thoroughly for best results.
Yes, scalpings are often used as an affordable and effective sub base material, particularly in garden paths, patios, and light-use areas. They compact well and offer good support when laid correctly.
To ensure a firm and level foundation, always compact your sub base using a vibrating plate compactor or roller. Work in layers no thicker than 75mm and pass over each layer two or three times for even compression.
Not all gravel is suitable as a sub base. Only well-graded gravel that compacts well, like Type 3 or a certified sub base material, should be used. Loose or rounded gravel won’t lock together and can cause instability under hard surfaces.
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