Aggregate/Ballast

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Work out ballast volume, aggregate tonnage, bulk bags, 25kg bags, cement quantity and estimated 2026 UK material cost for concrete slabs, footings, shed bases, fence posts and general groundwork.

What Is Ballast Aggregate?

Ballastis a pre-blended construction aggregate made from sharp sand and gravel or crushed stone. In the UK, it is commonly sold as10mm ballastor20mm ballastand is mainly used with cement and water to make concrete for foundations, slabs, shed bases, path edges, kerbs, fence posts and small domestic groundwork. It is popular because it saves time: instead of ordering separate sharp sand and gravel, you can use one all-in aggregate blend.

This Ballast Guide UK page is built for practical site estimating. It converts your length, width and depth into cubic metres, then converts the volume into kilograms, tonnes, bulk bags and small bags. It also gives a sensible allowance for wastage, compaction, moisture variation and uneven excavation so you are less likely to run short halfway through the pour.

2026 UK Density Rule Used by This Guide

For 20mm all-in ballast, the guide uses a working bulk density of 1,750kg per m³. Many UK suppliers and guides work around 1.75–1.8 tonnes per m³, but actual yield changes with moisture, grading, compaction and how the material is loaded into the bag.

Concrete Mixing

Ballast is most often mixed with cement and water for general concrete. For small domestic slabs, paths, garden bases and footings, all-in ballast is quick and convenient.

Bulk Bag Planning

Most UK ballast is delivered in 800kg or 850kg bulk bags. The guide rounds bag quantities up so your order reflects real merchant delivery units.

m³ to Tonnes

Length × width × depth gives volume. Volume × density gives weight. This is the simplest way to avoid under-ordering aggregate on site.

Ballast Working Formula — How to Convert m³ to Tonnes

The formula used by this aggregate tonnage guide is simple, but the accuracy depends on entering the correct finished depth. For a concrete slab, depth means the concrete thickness. For pipe bedding, depth means the bedding layer. For a general void fill, use the average depth if the ground is not level.

  • Step 1:Area = length × width
  • Step 2:Volume = area × depth in metres
  • Step 3:Weight in kg = volume × material density
  • Step 4:Tonnes = kg ÷ 1,000
  • Step 5:Bags = kg required ÷ bag weight, rounded up to the next whole bag

Quick Example

A 5m × 3m slab at 100mm depth gives 1.5m³. Using 1,750kg/m³ ballast density, the base requirement is 2,625kg or 2.63 tonnes. Add 10% wastage and the order becomes about 2.89 tonnes, equal to 4 × 850kg jumbo bags.

Why Wastage Matters

In theory, exact volume working are enough. On real UK sites, ballast is affected by spillage, compaction, damp material, irregular excavation, wheelbarrow losses and low spots in the base. For neat shuttered slabs, 5% may be fine. For hand-dug bases, rough ground or DIY mixing, 10% is safer. Where you are filling uneven ground, around drains or around posts, 15% can prevent an expensive second delivery.

Aggregate Density Table — UK Ballast, MOT Type 1, Sand & Gravel

Different aggregates have different weights. A cubic metre of sharp sand does not weigh the same as a cubic metre of MOT Type 1 or crushed hardcore. The table below gives practical working densities for estimating. They are not laboratory values; they are site-friendly guide values designed for ordering.

  • Material: 20mm All-In Ballast; Working Density: 1.75 t/m³; Approx. m³ per Tonne: 0.57m³; Best Use: Concrete slabs, footings, shed bases; Guide Note: Default
  • Material: 10mm Ballast; Working Density: 1.70 t/m³; Approx. m³ per Tonne: 0.59m³; Best Use: Smaller pours, tighter formwork; Guide Note: Smoother mix
  • Material: MOT Type 1 Sub-Base; Working Density: 2.00 t/m³; Approx. m³ per Tonne: 0.50m³; Best Use: Driveways, patios, paths; Guide Note: Not concrete ballast
  • Material: Sharp Sand; Working Density: 1.60 t/m³; Approx. m³ per Tonne: 0.63m³; Best Use: Bedding, screeding, paving layers; Guide Note: Moisture sensitive
  • Material: 20mm Gravel; Working Density: 1.65 t/m³; Approx. m³ per Tonne: 0.61m³; Best Use: Drainage, soakaways, decorative areas; Guide Note: Permeable
  • Material: Crushed Hardcore; Working Density: 1.90 t/m³; Approx. m³ per Tonne: 0.53m³; Best Use: Void filling and base build-up; Guide Note: Variable grading

Important Density Warning

Do not use one density for every aggregate. A tonne of MOT Type 1 covers less volume than a tonne of ballast because it is denser. A tonne of dry gravel or sharp sand can cover more volume. For critical structural work, confirm bulk density with the supplier and check the project specification.

How Many Bulk Bags of Ballast Do I Need?

UK merchants commonly supply ballast in800kg bulk bags,850kg jumbo bags, small 20–25kg bags, or loose loads by the tonne. A bulk bag is convenient for DIY and small trade work because it can be craned close to the work area and used gradually. Loose aggregate is usually better value for larger projects, but it needs space, suitable access and often quicker use.

For 20mm ballast at 1.75 tonnes per m³, one 850kg jumbo bag contains roughly0.49m³before wastage. One 800kg bulk bag contains roughly0.46m³. Coverage changes if the aggregate is wetter, compacted or measured after being tipped.

  • Delivery Unit: Jumbo Bag; Weight: 850kg; Approx. Volume at 1.75t/m³: 0.49m³; Coverage at 50mm: 9.7m²; Best For: Most domestic projects
  • Delivery Unit: Bulk Bag; Weight: 800kg; Approx. Volume at 1.75t/m³: 0.46m³; Coverage at 50mm: 9.1m²; Best For: DIY concrete work
  • Delivery Unit: Loose Load; Weight: 1 tonne; Approx. Volume at 1.75t/m³: 0.57m³; Coverage at 50mm: 11.4m²; Best For: Larger trade orders
  • Delivery Unit: Small Bags; Weight: 25kg; Approx. Volume at 1.75t/m³: 0.014m³; Coverage at 50mm: 0.29m²; Best For: Repairs and post holes

Ballast Price Guide UK 2026 — Per Tonne, Bulk Bag & Delivery

UK ballast pricing in 2026 depends on region, haulage distance, quarry source, bag size, merchant margin and delivery access. A single small DIY bag is expensive per tonne, while a loose load is usually cheaper if you have space for tipping. Bulk bags cost more per tonne than loose aggregate but are cleaner, easier to store and more convenient for homes with limited access.

Construction material prices moved upward again in early 2026, with official building-material statistics showing aggregate-related price pressure. GOV.UK also lists the Aggregates Levy rate from 1 April 2026 at £2.16 per tonne for taxable aggregate commercially exploited in England, Wales and Northern Ireland. This levy is not something a normal homeowner pays separately at the checkout, but it is part of the wider aggregate supply-cost environment.

2026 Cost Assumption Used by the Guide

The guide uses broad UK retail/trade estimating ranges, not live merchant prices. Use it for planning and quote checking, then confirm exact delivered pricing with your local supplier before ordering.

Loose Ballast

Usually best value for 3+ tonnes where a lorry can tip safely. Delivery and minimum order charges can change the final price significantly.

Bulk Bags

Cleaner and easier for domestic sites. Expect a higher price per tonne, but better control, less mess and simpler storage on driveways or front gardens.

Small Bags

Best only for small repairs, post holes or patching. Per-tonne cost is much higher, but collection and handling are easier for very small jobs.

What Can Increase Your Final Ballast Cost?

  • Delivery distance:Aggregates are heavy, so haulage can cost as much as the material on small orders.
  • Bagged delivery:Bulk bags include bagging, handling and crane-offload costs.
  • Access limits:Narrow lanes, weight limits, steep drives or restricted parking can increase delivery charges.
  • Regional labour and merchant rates:London and the South East usually cost more than many northern or rural areas.
  • Seasonal demand:Spring and summer DIY demand can reduce availability and raise delivery waiting times.

Ballast to Cement Ratio — How Much Cement Do You Need?

When ballast is used to make concrete, the aggregate guide is only half the job. You also need enough cement. For many domestic applications, people use cement-to-ballast ratios such as1:5or1:6by volume. Stronger mixes use more cement; weaker general-purpose fills use less. Always follow an engineer’s specification for structural foundations, extensions, retaining walls, garages and any load-bearing concrete.

  • Mix Ratio: 1:5 cement:ballast; Typical Use: Stronger domestic concrete; Cement Guide: Approx. 7–8 × 25kg bags per tonne ballast; Best For: Footings, bases, heavier garden work; Warning: Do not over-water
  • Mix Ratio: 1:6 cement:ballast; Typical Use: General concrete; Cement Guide: Approx. 6 × 25kg bags per tonne ballast; Best For: Shed bases, paths, fence posts; Warning: Not for engineered structural work
  • Mix Ratio: Specified ready-mix; Typical Use: Controlled concrete strength; Cement Guide: Ordered by m³ and grade; Best For: Extensions, garages, structural slabs; Warning: Follow engineer / Building Control

Structural Work Warning

Do not rely on a DIY ballast mix for structural work unless the specification allows it. For house extensions, load-bearing foundations, garage slabs and retaining walls, use an engineer-approved concrete grade and consult Building Control where required.

Common UK Ballast Working by Project

The guide works for any rectangular area, but the right depth depends on the job. Below are practical examples for homeowners and small contractors. Use these as starting points only. Ground conditions, load, reinforcement, drainage and local building requirements can change the final specification.

Shed Base

A small shed base is often 75–100mm thick, depending on shed size and ground. Add a compacted sub-base below where needed and keep the slab slightly above surrounding ground.

Driveway Warning

Ballast is not the same as MOT Type 1. For a driveway base, use specified compacted sub-base material, not loose ballast, unless your design specifically allows it.

Fence Posts

For post holes, work out the hole volume, subtract the post volume, then allow extra for over-digging. Small bags may be easier than bulk delivery for short fence runs.

Footings

Footings need correct width, depth and concrete strength. For structural footings, do not guess: follow drawings, engineer notes and any Building Control requirements.

Drainage Bedding

Ballast can sometimes be used as bedding or void fill, but clean gravel is often preferred for drainage because it is freer draining and contains less fine material.

Concrete Paths

For footpaths and garden paths, 75–100mm concrete is common for light pedestrian use, but heavy loads require a stronger base and sometimes reinforcement.

How to Order Ballast Correctly in 2026

Ordering ballast is not just about the number of tonnes. You also need to choose delivery format, confirm access, understand whether the price includes VAT, check if the merchant supplies 800kg or 850kg bags, and make sure the material is suitable for the work. Two suppliers may both advertise “bulk bag ballast” but one bag may be 800kg while another may be 850kg. That difference matters when you work out coverage.

Before You Order, Check These Details

  • Bag weight:Confirm whether the bag is 800kg, 850kg or another stated minimum fill.
  • Aggregate size:20mm all-in ballast is common for general concrete; 10mm may suit tighter pours.
  • Delivery method:Crane-offload, kerbside delivery, loose tipping and pallet delivery all have different access needs.
  • VAT:Many trade prices are shown excluding VAT; retail pages may show VAT included.
  • Lead time:Book delivery before mixing day so you are not waiting for material while cement and labour are ready.
  • Storage:Keep ballast on a clean, firm surface and avoid contaminating it with soil, leaves or standing water.

Best Ordering Rule

If the guide says 2.05 bulk bags, order 3 bags. Aggregates are sold in whole bags, and running short on a concrete pour creates cold joints, weak patches and delays.

How to Measure for Ballast — Rectangles, Trenches, Circles & Irregular Areas

Most ballast guides ask for length, width and depth because many slabs and bases are rectangular. Real sites are not always that tidy. A garden base may be L-shaped, a foundation trench may run around several walls, and a set of post holes may be circular. The easiest way to stay accurate is to break the job into small simple shapes, work out each section separately, then add the totals together.

For an L-shaped shed base, split the shape into two rectangles and work out each one. For a trench, measure the total trench length, average trench width and concrete depth. For circular post holes, use the hole radius and depth to work out the cylinder volume. For irregular ground, take several depth measurements and use the average rather than the shallowest point. This avoids under-ordering when the dig is deeper at one side.

Rectangular Slabs

Use length × width × depth. This is ideal for shed bases, garage pads, garden paths, concrete bases and simple rectangular footings.

Trenches

Use total trench length × average trench width × fill depth. Measure width after digging, not only from the plan, because trench sides often break away.

Post Holes

For round holes, work out each hole as a cylinder and multiply by the number of holes. Subtracting post volume improves accuracy for large timber posts.

Measuring Depth Correctly

Depth is the most common source of error in an aggregate tonnage working. A 5m × 3m slab at 100mm is 1.5m³, but the same slab at 125mm is 1.875m³. That 25mm change adds more than half a tonne of ballast. Before ordering, check the depth after excavation with a tape measure at several points. If the base is uneven, work out using the average depth or the deepest practical design depth, then apply a sensible wastage allowance.

For concrete work, remember that the ballast volume is linked to the finished concrete volume, not the loose heap size. When ballast is mixed with cement and water, voids between the stones and sand are filled and the final wet concrete volume is not identical to the loose aggregate pile. This is why practical UK ballast estimates use weight per cubic metre of finished concrete, then add an allowance for site handling.

Ballast vs MOT Type 1 vs Gravel vs Sharp Sand — Which One Should You Work out?

Many people search for a ballast guide when they actually need a general aggregate guide. The difference matters because each material has a different job. Ballast is a ready-mixed sand and stone blend for concrete. MOT Type 1 is a compactable sub-base. Gravel is used for drainage, decorative surfaces and soakaways. Sharp sand is used for bedding, screeding and some mortar or concrete blends, but it is not a direct replacement for all-in ballast.

If you are pouring concrete, choose 10mm or 20mm ballast in the guide. If you are building a driveway or patio base below paving, choose MOT Type 1. If you are filling a French drain, trench drain or soakaway, clean gravel is usually better than ballast because it drains more freely. If you are laying paving blocks, you may need sharp sand for the bedding layer and MOT Type 1 below it.

Do Not Swap Materials Without Checking the Specification

Using ballast where compacted Type 1 is required can lead to settlement. Using Type 1 in a concrete mix is not a normal substitute for all-in ballast. Using sharp sand alone removes the coarse aggregate needed for many concrete mixes.

Best Material by Job

  • Concrete slab:20mm ballast with cement and water, unless a specified ready-mix grade is required.
  • Small concrete repair:10mm ballast may be easier to place in shallow or narrow areas.
  • Driveway sub-base:MOT Type 1 or a specified compacted sub-base material.
  • Drainage trench:Clean gravel or drainage stone, usually not ballast with fines.
  • Paving bedding:Sharp sand or grit sand as specified by the paving system.
  • Void filling:Hardcore, gravel or ballast depending on drainage and compaction requirements.

Practical Ballast Quantity Examples for UK DIY Projects

These worked examples show how quickly ballast quantities increase with depth. They also show why ordering by “a few bags” can be risky. A small increase in slab thickness can add several hundred kilograms. For every example below, the final order should be rounded up to available delivery units and checked against your site conditions.

  • Project Example: 3m × 2m shed base at 100mm; Volume: 0.60m³; Ballast Before Wastage: 1.05t; With 10% Allowance: 1.16t; 850kg Bags: 2 bags
  • Project Example: 5m × 3m slab at 100mm; Volume: 1.50m³; Ballast Before Wastage: 2.63t; With 10% Allowance: 2.89t; 850kg Bags: 4 bags
  • Project Example: 10m footing trench × 450mm × 300mm; Volume: 1.35m³; Ballast Before Wastage: 2.36t; With 10% Allowance: 2.60t; 850kg Bags: 4 bags
  • Project Example: 2m × 2m base at 75mm; Volume: 0.30m³; Ballast Before Wastage: 0.53t; With 10% Allowance: 0.58t; 850kg Bags: 1 bag
  • Project Example: 6m × 1m path at 100mm; Volume: 0.60m³; Ballast Before Wastage: 1.05t; With 10% Allowance: 1.16t; 850kg Bags: 2 bags

Why the Guide Rounds Up

If your result is 1.16 tonnes and your supplier delivers 850kg bags, one bag is not enough. The guide rounds up because partial bulk bags are not normally available, and under-ordering can delay the pour.

Common Ballast Guide Mistakes to Avoid

A ballast guide is only as good as the measurements entered. Most problems come from mixing units, forgetting to convert millimetres to metres, ordering exact quantities with no allowance, or selecting the wrong material. Avoid these mistakes before you place a merchant order.

  • Using 100 instead of 0.1 metres:If working out manually, 100mm is 0.1m, not 100m. The guide handles unit conversion for you.
  • No wastage allowance:Exact working rarely match real-life digging, mixing and barrowing. Add at least 5% for clean jobs and 10% for general DIY work.
  • Ignoring bag size:One supplier may supply 800kg bags while another supplies 850kg bags. That changes the number of bags needed.
  • Confusing ballast with sub-base:Ballast is not the default driveway base material. Use the right aggregate for the layer you are building.
  • Forgetting cement:Ballast alone does not make concrete. You need cement and water, or you need to order ready-mix concrete.
  • Not checking access:Bulk bags need suitable kerbside or driveway delivery access. Loose loads need a safe tipping area.

For the best result, measure twice, work out once, then compare your guide result with a supplier quote. If the quote is much lower than your determined tonnage, ask what density, bag weight and wastage allowance they used. If the quote is much higher, ask whether delivery, VAT, extra bags, minimum order charges or different material grades are included.

UK Aggregate Standards, Levy & Useful 2026 References

Ballast and aggregates used in concrete are part of a wider construction materials system. Quality, grading and use should match the project specification. For concrete aggregates, UK practice references standards such as BS EN 12620 and related guidance. For larger projects, always check specification documents rather than relying only on a retail label.

Use This Guide for Estimating — Confirm Critical Projects Professionally

This resource gives practical UK estimating values for ballast, aggregate tonnage and delivery bags. For structural concrete, foundations, retaining walls, garages, extensions or commercial work, confirm mix design, depth, reinforcement and specification with a qualified contractor, structural engineer or Building Control professional.

Ballast Guide UK — FAQs

Common questions about ballast volume, aggregate tonnage, bulk bags, cement ratios, density and UK ordering in 2026.

1,750kg to 1,800kg of ballast per cubic metre

3 jumbo bags

40 bags of 25kg ballast in one tonne

20mm ballast

10mm ballast

6 × 25kg cement bags per tonne of ballast

Related UK Building & Aggregate Guides

Use these related guides to estimate concrete, driveway, patio, sub-base and home improvement material quantities.

For additional concrete quantity and estimating resources, you can also visit ConcreteCalcs.com.

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