MOT Type 1 Calculator

How Much MOT Type 1 Do I Need?

This free sub-base calculator works out exactly how much MOT Type 1, crusher run, scalpings or sharp sand you need for any foundation project. Enter your area in metres or feet, set the depth in millimetres or inches, choose your material, and get an instant answer in cubic metres, tonnes, bulk bags and 25kg bags.

The calculator uses the formula length × width × depth to find the volume, then multiplies by the density of your chosen material. MOT Type 1 is the heaviest at 2,100 kg/m³, while sharp sand is lighter at 1,600 kg/m³. Getting the density right is important because sub-base materials are sold by weight in the UK.

This calculator also works as a hardcore calculator — select “Hardcore / Recycled aggregate” from the material dropdown to get quantities for bulk fill and backfilling projects.

This calculator also works as a general aggregate calculator — enter any material density to estimate tonnage for sand, gravel, ballast or decorative aggregates.

Need to calculate the surface layer too? Our gravel calculator works out decorative stone quantities, the paving calculator handles slab counts for patios, and the concrete calculator covers shed bases and fence post foundations.

Recommended Sub-Base Depths by Project

The right depth depends on the ground conditions and what the surface will support.

MOT Type 1 vs Type 3 vs Crusher Run

Different sub-base materials have different properties. Here's how they compare.

How to Lay a Sub-Base

A properly laid sub-base is the foundation of any hard landscaping project. Getting this right prevents sinking, cracking and drainage problems later.

1. Excavate to the right depth

Dig out the area to your required depth plus the thickness of the surface layer (paving slabs, gravel, etc.). Allow for the sub-base, bedding layer and surface material. For a patio with 50mm paving on 30mm sand bedding over 100mm sub-base, you need to excavate 180mm total.

2. Compact the subgrade

Before adding any material, compact the bare ground with a plate compactor or roller. This prevents settlement. If the ground is soft clay, consider laying geotextile membrane on top to stop the sub-base mixing into the clay.

3. Lay and compact the sub-base

Add MOT Type 1 or crusher run in layers of no more than 75mm (3 inches) at a time. Compact each layer with a plate compactor before adding the next. For a 150mm sub-base, that's two passes. The finished surface should be level and firm enough to walk on without leaving footprints.

MOT Type 1 Coverage Per Tonne

The area that one tonne of MOT Type 1 covers depends on the depth you lay it. Use this quick reference table to estimate quantities without a calculator.

These figures assume a density of 2,100 kg/m³ for MOT Type 1 (uncompacted). After compaction with a plate compactor, the material settles by roughly 10–15%, so always order 10% more than calculated to account for this.

Hardcore vs MOT Type 1 — Which Do You Need?

“Hardcore” and “MOT Type 1” are often used interchangeably, but they’re not the same thing. Understanding the difference helps you choose the right material and avoid overspending.

What is hardcore?

Hardcore is a general term for any broken or crushed material used as fill — typically recycled brick, concrete rubble, or mixed demolition waste. It’s cheaper than MOT Type 1 but less consistent in grading. You might see it called “clean hardcore”, “recycled aggregate”, or “6F2 fill”.

When to use hardcore

Hardcore is fine for backfilling trenches, raising levels, or as a bulk fill layer under a proper sub-base. It’s not recommended as the final sub-base layer under paving or driveways because the irregular sizing makes it difficult to compact to a flat, stable surface.

When to use MOT Type 1

MOT Type 1 is the industry standard sub-base for any hard landscaping project — driveways, patios, paths and shed bases. Its graded particle sizes (40mm down to dust) interlock when compacted, creating a solid, load-bearing foundation. If you’re laying paving slabs, block paving or gravel on top, always use MOT Type 1 for the final sub-base layer.

Pro tip: For budget-conscious projects, lay a thick layer of hardcore as bulk fill, then finish with 100mm of MOT Type 1 on top. This gives you a solid, compactable surface at lower cost than using MOT Type 1 throughout.

Planning to lay tarmac on top of your sub-base? Use our tarmac calculator to work out how much tarmac or asphalt you need for your driveway, path or car park.

How Much Hardcore Do I Need?

To calculate how much hardcore you need, the process is identical to calculating MOT Type 1 — multiply length × width × depth (all in metres) to get the volume in cubic metres, then multiply by the density. Hardcore is slightly lighter than MOT Type 1 at roughly 1,900–2,000 kg/m³ because it has more voids between particles.

Hardcore Worked Example

Suppose you need to backfill a 4m × 3m area to a depth of 200mm (0.2m) with hardcore before laying MOT Type 1 on top:

• Volume: 4 × 3 × 0.2 = 2.4 cubic metres
• Weight: 2.4 × 1,950 = 4,680 kg = 4.68 tonnes
• Bulk bags (850kg): 4,680 ÷ 850 = 6 bulk bags

Use the calculator at the top of this page to run the numbers for your project — simply enter your area and depth, and the results work for hardcore, MOT Type 1, crusher run or any aggregate with a similar density. For hardcore specifically, reduce the result by about 5–10% since it is lighter per cubic metre than graded sub-base.

How Much Does MOT Type 1 Cost?

Prices vary by region and supplier, but here are typical UK costs for MOT Type 1 sub-base as of 2026.

Delivery charges typically add £30–£80 depending on distance from the quarry. For quantities over 5 tonnes, always get quotes from local aggregate suppliers — you’ll pay a fraction of the bag price. Many suppliers offer free delivery above a minimum order (usually 10–20 tonnes).

Frequently Asked Questions

Types of Sub-Base Aggregate

Choosing the right sub-base aggregate is one of the most important decisions in any groundwork project. Each material has different particle sizes, compaction characteristics and drainage properties. I have seen plenty of patios and driveways fail because the wrong type was used, so here is a proper breakdown of the five main sub-base aggregates you will encounter in the UK.

MOT Type 1 (Primary Crushed Rock)

MOT Type 1 is the gold standard for sub-base work in the UK. It consists of primary crushed limestone, granite or basalt, graded from 40mm particles down to fine dust. The mix of sizes is deliberate — the fines fill the gaps between the larger stones, creating an interlocking matrix that compacts into an extremely dense, stable layer. When properly compacted, Type 1 can support the weight of heavy vehicles without shifting. It drains slowly because the fines make it almost waterproof once compacted, which is ideal under impermeable surfaces like block paving and tarmac. For most domestic projects — driveways, patios, shed bases, paths — MOT Type 1 is the correct choice.

MOT Type 3 (Open-Graded, Free-Draining)

MOT Type 3 is a single-size clean stone, typically 40mm, with no fines at all. Because every particle is roughly the same size, there are large voids between the stones that allow water to flow through freely. This makes Type 3 the go-to material for drainage applications: soakaways, French drains, permeable paving bases, and any project where you need water to infiltrate rather than sit on the surface. It does not compact into a solid layer like Type 1, so it is not suitable as the sole sub-base under a load-bearing surface. You can, however, use it as a drainage layer beneath a Type 1 sub-base on waterlogged sites.

Recycled Aggregate (6F2)

Recycled aggregate, commonly sold under the Highways England specification 6F2, is made from crushed concrete, brick and stone recovered from demolition sites. It is screened and graded to produce a particle distribution similar to MOT Type 1. The environmental benefit is obvious — it diverts waste from landfill — but the practical benefit is cost. Recycled aggregate typically sells for 20–30% less per tonne than virgin crushed rock. For domestic driveways, patios and garden paths, 6F2 performs comparably to Type 1. The one caveat is consistency: buy from a reputable supplier who tests their batches, because poorly screened recycled aggregate can contain oversized lumps or contaminants.

Scalpings

Scalpings are the thin, flat fragments left over when quarries crush and screen larger stone. They tend to be angular and relatively uniform in size, typically 10–40mm with fewer fines than MOT Type 1. Scalpings compact reasonably well and are often used for temporary surfaces, farm tracks, rural paths and as a levelling layer. They are not recommended as the primary sub-base under driveways or patios because the lack of fine particles means they do not lock together as tightly as Type 1. However, they are cheap and readily available, making them a practical choice for less demanding applications.

Crusher Run

Crusher run is a general trade term for the material that comes straight out of the crushing process at a quarry, before it is screened to a specific grading. It contains a mix of sizes from large chunks down to dust, broadly similar to MOT Type 1 but without the strict grading specification. For domestic projects where you are not required to meet a highways specification, crusher run works perfectly well and usually costs a few pounds less per tonne. It compacts solidly, supports heavy loads, and is widely available from local quarries and aggregate suppliers.

If you are unsure which aggregate to use, MOT Type 1 is the safe default for any load-bearing project. For drainage-specific work, switch to Type 3. And for budget builds where highways compliance is not required, recycled 6F2 or crusher run will save you money without sacrificing performance.

How to Lay a Sub-Base: Step-by-Step Guide

A properly laid sub-base is the single most important factor in the longevity of any patio, driveway or path. I have repaired more sunken patios caused by poor sub-base work than I care to count. Here is the process I recommend, step by step.

Step 1: Mark Out and Excavate

Mark out your area using string lines and pegs. Excavate to the total depth you need — this includes the sub-base, any bedding layer, and the surface material. For a typical patio with 50mm paving slabs on a 30mm sand bed over 100mm of sub-base, you need to dig out 180mm below your finished surface level. For a driveway with block paving (50mm) on 30mm sand over 150mm sub-base, excavate 230mm. Use a spade and wheelbarrow for small areas, or hire a mini digger (roughly £150–£200 per day) for anything over 10 square metres. Check your levels regularly with a spirit level and straight edge.

Step 2: Lay Geotextile Membrane on Soft Ground

If your subsoil is clay, silt, or anything soft enough to leave a footprint when you stand on it, lay a geotextile membrane across the entire excavated area. Overlap sheets by at least 300mm. The membrane acts as a separation layer, preventing the sub-base aggregate from being pushed down into the soft subsoil by traffic and weather. Without it, your carefully compacted sub-base will gradually sink into clay soil over a few years, taking your paving with it. On firm, well-drained ground (gravel, chalk, sandy subsoil), you can skip this step.

Step 3: Spread Sub-Base in Thin Layers

This is where most DIYers go wrong. Do not dump the full depth of sub-base in one go and compact the top. A plate compactor (also called a wacker plate) can only effectively vibrate material to a depth of about 50–75mm. Anything deeper stays loose underneath. Spread your first layer at no more than 50mm thickness, rake it roughly level, then compact it. Add the next 50mm layer, compact again. For a 150mm sub-base, that is three passes. Yes, it takes longer. No, there is no shortcut that works.

Step 4: Compact Each Layer Thoroughly

Hire a plate compactor for roughly £25–£35 per day from any tool hire shop. Run it across each layer in overlapping passes, working from the edges inward. You want to make at least three full passes over every section. The surface should feel solid underfoot — if you can leave a footprint in the compacted sub-base, it needs more work. For small areas like a single shed base, a hand tamper will do the job, though it requires considerably more effort.

Step 5: Check Levels and Drainage Falls

Once your final layer is compacted, check the surface is level using a long spirit level or a straight timber edge. The sub-base should fall very slightly away from any buildings — a gradient of 1:80 (roughly 12mm per metre) is standard. This ensures rainwater drains away from your house. If any areas are high or low, add or remove material and re-compact. Getting this right now saves you from relaying paving later. Once the sub-base is level, firm and draining correctly, you are ready for your bedding layer and surface material. Our paving calculator can help you work out how many slabs you need, or use the concrete calculator for a slab base.

Why Compaction in Layers Matters

Compaction in layers is not optional — it is the difference between a patio that lasts 20 years and one that starts sinking after two winters. When you compact a thin layer of MOT Type 1, the vibration forces the fine particles into the gaps between the larger stones, creating a dense, interlocked matrix. If you try to compact 150mm or more in one pass, only the top 50–75mm gets properly compacted. The bottom half remains loosely packed. Over time, traffic and the freeze-thaw cycle will cause the loose material to settle, creating dips, cracks and uneven surfaces above. Professionals always compact in layers — and there is a good reason for it.

Sub-Base Cost Guide UK 2026

Understanding the true cost of sub-base material helps you budget accurately and avoid nasty surprises. The price per tonne varies dramatically depending on how you buy it — small bags from a DIY shop can cost ten times more per tonne than a loose delivery from a quarry. Here is a breakdown of real-world UK prices as of early 2026.

Price by Purchase Format

The most expensive way to buy sub-base is in 25kg bags from B&Q or Wickes. At £5–£7 per bag, you are paying £200–£280 per tonne — perfectly fine for a single fence post hole, but ruinous for a driveway. Bulk bags (850kg) cost £50–£70 each, bringing the per-tonne price down to around £60–£82. For any project requiring more than 2 tonnes, loose delivery from a local aggregate supplier or quarry is the most cost-effective option at £35–£55 per tonne plus a delivery charge of £30–£80 depending on distance. Many quarries offer free delivery on orders above 10 tonnes.

Project Cost Estimates

To give you a practical idea of what sub-base costs for real projects, here are worked examples using MOT Type 1 at mid-range pricing (£45 per tonne loose delivery, plus £50 delivery charge). These include only the sub-base material — add your surface material, bedding sand, and any hire costs on top.

These estimates include 10% extra for compaction and wastage. If you want to cut costs without cutting quality, consider using recycled 6F2 aggregate instead of virgin MOT Type 1 — the material itself costs 20–30% less, potentially saving £50–£100 on a driveway project. You can also collect material yourself from a local quarry or builders’ merchant to avoid the delivery charge, provided you have a suitable vehicle or trailer.

5 Common Sub-Base Mistakes (and How to Avoid Them)

After years of helping people plan groundwork projects, I see the same mistakes come up again and again. Every single one of these leads to a failed surface — sunken paving, cracked concrete, pooling water. Here is what to watch out for.

1. Not Going Deep Enough

This is the number one mistake. A driveway needs 150mm of compacted sub-base as an absolute minimum. I regularly see people lay 75mm under a driveway because “it is only a car.” A family car weighs 1,200–1,800kg, and that load is concentrated on four small tyre contact patches. On 75mm of sub-base, the aggregate shifts under repeated loading, and within a year or two you get ruts and dips. For patios, 100mm is the minimum. For paths, you can get away with 75mm. But for driveways, 150mm is non-negotiable — and 200mm is better if you have clay soil or heavy vehicles visiting.

2. Compacting the Full Depth in One Pass

I covered this in the laying guide above, but it bears repeating because it is so common. A plate compactor vibrates the top 50–75mm of material. If your sub-base is 150mm deep and you compact once, you have a firm 75mm crust over a loose 75mm foundation. The bottom layer settles slowly over weeks and months, taking your paving with it. Always compact in layers of no more than 50–75mm. It doubles the time, but it is the only way to get a genuinely solid base.

3. Using MOT Type 3 Where Type 1 Is Needed

Type 3 is a drainage aggregate. It is single-size clean stone with no fines, which means it does not compact into a solid, load-bearing layer. I have seen driveways laid on Type 3 where the block paving sinks unevenly because the stones shift under load. Type 3 is brilliant in soakaways, French drains and as a drainage layer under permeable paving — but it should never be used as the main structural sub-base under a conventional driveway or patio. If you need drainage and load-bearing capacity, lay Type 3 at the bottom for drainage, then top it with 100mm of Type 1 for structure.

4. Skipping Geotextile Membrane on Clay Soil

Clay soil is the enemy of sub-bases. It is soft, it holds water, and it expands and contracts with the seasons. If you lay MOT Type 1 directly onto clay, the aggregate slowly gets pushed down into the clay by traffic and vibration. Over a few years, you lose depth and stability. A geotextile membrane between the clay and the sub-base costs just £15–£30 for enough to cover a typical driveway. It prevents the aggregate mixing with the subsoil and keeps your sub-base at full depth for decades. On sandy or gravelly subsoil, you do not need it. On clay, you absolutely do.

5. Ignoring Drainage

Water is the second biggest cause of sub-base failure after insufficient depth. If water cannot drain away from under your paving, it saturates the sub-base and softens the subsoil beneath. In winter, trapped water freezes and expands, heaving the surface upward. When it thaws, the surface drops back — but not evenly, leaving you with cracks and dips. Always ensure your sub-base has a slight fall (1:80 gradient, about 12mm per metre) directing water away from buildings and toward a drain, soakaway or garden. If your site has naturally poor drainage, consider laying a land drain around the perimeter before you start the sub-base, or use a Type 3 drainage layer underneath your Type 1 structural layer. Our gravel calculator can help you plan a gravel drainage border around the finished surface.

Best Sub-Base & Groundwork Products UK 2026 — Our Top Picks

These are the most popular sub-base materials and groundwork essentials available in the UK right now — everything you need for a solid foundation.

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Where to Buy Sub-Base in the UK

For quantities over 1 tonne, bulk bags or loose delivery from a local aggregate supplier is the most cost-effective option.

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