Base/Sub-base Guide | ConcreteMaths.com

This article covers Base/Sub-base, with practical UK guidance, examples and key points to consider before planning or ordering materials.

Work out how much MOT Type 1, Type 3, crushed concrete, hardcore, gravel or compacted aggregate you need for a driveway, patio, path, shed base, concrete slab or landscaping project in 2026.

Base/Sub-base Guide UK 2026

A reliable base or sub-base is what stops paving, concrete, gravel, decking supports, sheds and driveways from sinking, rutting, rocking or cracking. The visible surface may be porcelain slabs, block paving, resin, gravel, tarmac or concrete, but the long-term performance depends on the hidden compacted aggregate layer underneath. This UK base/sub-base guide converts length, width and depth into cubic metres, tonnes, bulk bags, 25kg bags and a realistic 2026 supply-cost estimate.

the working method is designed for domestic and small commercial estimating: patios, paths, driveway sub-bases, shed bases, garage bases, workshop slabs, permeable driveways, garden rooms, hot-tub pads and general landscaping. It includes common UK aggregate materials such as MOT Type 1, MOT Type 3, recycled Type 1, crushed concrete, hardcore, crusher run, sharp sand, granite dust, ballast and drainage gravel. Because aggregate density changes by quarry, moisture content and grading, the result should be treated as a practical ordering estimate rather than a structural design certificate.

For most homeowner projects, the key working is simple: area multiplied by compacted depth gives the required compacted volume. The complication is that sub-base is usually delivered loose and then compacted in layers. Loose aggregate settles under a plate compactor or roller, so you normally order more than the final compacted volume. This page applies an adjustable loose-to-compacted allowance, a wastage allowance, a material density and a bag or lorry delivery size to help you order enough material without massively overbuying.

2026 estimating note

UK aggregate prices remain regional and change with haulage, quarry availability, fuel, bagging and labour. GOV.UK lists the Aggregates Levy rate for taxable aggregate at£2.16 per tonne from 1 April 2026, while broader construction material price statistics are published through the officialbuilding materials and components statistics.

Volume First

Start with area and compacted depth. the working method converts those figures into compacted cubic metres before adding allowances.

Then Convert to Tonnes

Sub-base is usually sold by bulk bag or tonne, so density is used to estimate the weight needed for your project.

Order Practically

Results include bulk bags, small bags and cost guidance so you can compare merchant delivery, loose loads and collection.

Recommended Sub-base Depths for UK Projects

Sub-base depth depends on load, ground conditions, drainage and the surface being installed. A garden path over firm soil does not need the same support as a driveway carrying family cars every day. A patio on stable ground may work with a modest compacted layer, while a driveway over clay soil may need deeper excavation, geotextile separation, a thicker aggregate layer and careful compaction in more than one pass.

Use the figures below as practical domestic estimating guidance only. For adoptable highways, commercial yards, retaining structures, poor made ground or projects near buildings, you should follow the project specification from your engineer, architect, local authority or supplier. National Highways’Manual of Contract Documents for Highway Worksis the formal reference suite used for highway construction specifications, including unbound pavement mixtures.

Project: Garden path; Typical Compacted Depth: 50–75mm; Common Material: Type 1, Type 3 or gravel; Notes: Light foot traffic
Project: Patio / seating area; Typical Compacted Depth: 75–100mm; Common Material: MOT Type 1 below bedding layer; Notes: Standard domestic
Project: Domestic driveway — cars; Typical Compacted Depth: 150mm; Common Material: MOT Type 1 or Type 3 permeable; Notes: Vehicle loading
Project: Vans / heavier domestic use; Typical Compacted Depth: 175–225mm; Common Material: Type 1 in layers; Notes: Higher load
Project: Shed / garden room base; Typical Compacted Depth: 100–150mm; Common Material: Type 1 plus levelling layer; Notes: Depends on building weight
Project: Concrete slab support; Typical Compacted Depth: 100–150mm+; Common Material: Type 1, hardcore or engineered fill; Notes: Check slab design
Project: Permeable driveway; Typical Compacted Depth: 150–250mm+; Common Material: MOT Type 3 / open graded stone; Notes: SuDS friendly

Depth is not just a cost choice

Reducing sub-base depth may save money at installation, but it often causes settlement, ruts, rocking paving slabs and cracked joints. On weak clay, made ground or areas used by vans, deeper construction and a geotextile membrane may be cheaper than future repairs.

Sub-base Material Density & Uses

The same volume of different materials can weigh very different amounts. A cubic metre of compacted MOT Type 1 can be close to two tonnes, while dry topsoil or light landscaping aggregate can be far lighter. Merchants may quote bulk bags by approximate weight, loose aggregate by tonne, or small bags by 20kg or 25kg. This is why the working method shows both volume and weight.

MOT Type 1 is the common all-rounder for patios, slabs and non-permeable driveways. It contains a graded mix of stone sizes and fines, so it compacts tightly into a strong layer. MOT Type 3 is more open graded and drains better, so it is often selected for permeable surfacing systems. Recycled Type 1 and crushed concrete can be excellent value, but quality depends heavily on grading, contamination control and supplier consistency.

Material: MOT Type 1; Approx. Density: 2.00 tonnes/m³; Typical 2026 Cost/Tonne: £45–£75; Best Use: Patios, driveways, slabs, shed bases
Material: MOT Type 3; Approx. Density: 1.90 tonnes/m³; Typical 2026 Cost/Tonne: £50–£85; Best Use: Permeable driveways and SuDS bases
Material: Crushed concrete / recycled Type 1; Approx. Density: 1.85 tonnes/m³; Typical 2026 Cost/Tonne: £30–£60; Best Use: Budget sub-base, yards, landscaping
Material: Clean hardcore / crusher run; Approx. Density: 1.80 tonnes/m³; Typical 2026 Cost/Tonne: £35–£65; Best Use: General fill and deeper base layers
Material: Granite dust / grano dust; Approx. Density: 1.70 tonnes/m³; Typical 2026 Cost/Tonne: £50–£90; Best Use: Levelling and fine bedding layers
Material: Sharp sand; Approx. Density: 1.65 tonnes/m³; Typical 2026 Cost/Tonne: £40–£70; Best Use: Bedding, screeding, laying courses
Material: Pea gravel / drainage gravel; Approx. Density: 1.60 tonnes/m³; Typical 2026 Cost/Tonne: £55–£95; Best Use: Drainage layers, decorative gravel
Material: Ballast; Approx. Density: 1.75 tonnes/m³; Typical 2026 Cost/Tonne: £45–£80; Best Use: Concrete mixing, not ideal as primary sub-base

Choosing Type 1 vs Type 3

Use MOT Type 1 when you need a dense, well-compacted base for conventional paving or slabs. Use Type 3 or another open-graded aggregate where the surface system must remain permeable and allow water to pass through to a suitable drainage layer.

How to Work out Sub-base Quantity Manually

The base/sub-base guide uses the same logic a contractor would apply when creating a first-pass material estimate. First, work out the area in square metres. Second, convert the proposed compacted depth into metres. Third, multiply area by depth to get compacted cubic metres. Fourth, multiply by a loose-to-compacted allowance because delivered aggregate compacts and settles. Finally, multiply by density to convert cubic metres into tonnes.

For example, a 6m × 3m driveway area at 150mm compacted depth has an area of 18m². A 150mm depth is 0.15m, so the compacted volume is 18 × 0.15 = 2.70m³. If you add a 15% compaction allowance, the loose ordering volume becomes 3.105m³. Using MOT Type 1 at around 2.0 tonnes/m³, the order weight is approximately 6.21 tonnes before any final wastage allowance. That could mean around seven or eight 850kg bulk bags, or a loose delivery if access allows.

Small mistakes in depth make a big difference. Increasing depth from 100mm to 150mm raises volume by 50%. On a driveway, this may be necessary; on a light garden path, it may be overkill. The best practice is to measure the finished paved level, the excavated formation level, the bedding layer thickness and the paving/slab thickness together so the sub-base depth fits the total build-up.

Core working

Compacted volume = length × width × depth. Loose ordering volume is then adjusted for compaction and wastage. Weight is determined by multiplying the final volume by the selected material density.

Measure Area

For rectangles, multiply length by width. For irregular shapes, split the area into rectangles and triangles, then add them together.

Set Compacted Depth

Use the finished compacted layer depth, not the loose depth tipped from the bag or lorry.

Add Allowance

Compaction, uneven excavation, edge trimming and spillage normally require a small extra quantity.

Compaction, Layers and Geotextile Membranes

Sub-base should usually be compacted in layers rather than dumped to full depth in one go. A small DIY plate compactor is effective for many patios and paths, but it cannot properly compact very deep layers in a single pass. A common approach is to place, level and compact aggregate in 75–100mm layers. Deeper driveway or slab bases may need two or more layers, especially if the ground is uneven or soft.

Good compaction is not just about strength. It also affects surface levels, drainage and how evenly the finished paving sits. Loose pockets under slabs or blocks can settle after the first winter, leaving depressions that collect water. For driveways, poor compaction shows as wheel tracks, edge spread or ruts. Compacting each layer until the plate no longer leaves visible movement is usually a better result than relying on extra depth alone.

A geotextile membrane is often useful when the subgrade is clay, soft soil, made ground or likely to pump fines up into the aggregate. The membrane separates the soil from the sub-base, helping maintain the granular layer’s strength. For drainage applications, use a suitable permeable geotextile rather than an impermeable weed membrane that may trap water in the wrong place.

Patios:compact the Type 1, then add the bedding mortar or sand layer separately.
Block paving:compact sub-base thoroughly before laying sharp sand or grit bedding.
Concrete slabs:compact the base and confirm any DPM, insulation and reinforcement details before pouring.
Permeable systems:avoid dense fines where the design relies on water moving through the structure.
Soft ground:consider geotextile separation and a deeper sub-base rather than just adding more bedding sand.

Do not use sand as a structural sub-base

Sharp sand can be a laying or bedding layer, but it is not a substitute for a properly compacted granular sub-base under vehicle areas or heavy slabs. Too much loose sand can hold water, shift under load and cause paving movement.

Permeable Driveways, Drainage and Planning Rules

Sub-base design is especially important for front garden driveways because drainage affects planning permission. In England, if the new or replacement front garden surface is over 5m² and uses traditional impermeable surfacing that does not drain to a permeable area, planning permission may be required. ThePlanning Portal driveway guidanceand GOV.UK’spermeable surfacing of front gardens guidanceexplain the principle.

A permeable driveway is not just a permeable top layer. The base construction must support the paving and still allow water to pass, store or discharge safely. This often means an open-graded sub-base such as Type 3, clean angular stone or a proprietary permeable system rather than standard MOT Type 1 with lots of fines. The correct solution depends on soil infiltration, driveway gradient, proximity to buildings, water table, tree roots and whether runoff is sent to a soakaway, rain garden or other drainage feature.

When the working method’s permeable option is selected, it warns against dense Type 1 where permeability is the priority. This does not replace a drainage design, but it helps prevent a common mistake: buying a non-permeable dense aggregate and then installing a surface that was expected to be SuDS friendly.

Water Must Go Somewhere

A permeable surface must connect to a base and ground/drainage system that can accept the runoff.

Open-Graded Aggregate

Type 3 and clean angular stone have fewer fines and are usually better for permeable build-ups.

Check Local Rules

Conservation areas, listed buildings, highway crossings and dropped kerbs may add separate approvals.

Base/Sub-base Cost Guide UK 2026

Sub-base material cost is affected by quarry distance, delivery method, bagging, local demand, fuel, VAT and whether the aggregate is virgin or recycled. Loose tipped loads are normally cheaper per tonne than bulk bags, but they require space for delivery and may not be practical on tight streets. Bulk bags are convenient and cleaner, but you pay for bagging, transport and handling. Small 20kg or 25kg bags are useful for tiny repairs, but they become expensive and labour-intensive for driveways or large patios.

As a rough 2026 homeowner guide, MOT Type 1 might be quoted anywhere from the mid £40s to £75+ per tonne depending on area and order size. Recycled crushed concrete may be cheaper, while decorative or specialist permeable aggregates can cost more. London, the South East and remote areas can be more expensive because haulage and access constraints are significant. the working method applies broad regional multipliers only; always check live prices from local builders’ merchants, quarries and landscape suppliers before ordering.

VAT is another source of confusion. Some online prices are displayed including VAT, while trade quotes may show net prices. this guide includes a VAT checkbox so you can view an approximate fully inclusive figure. Delivery may also be charged separately, especially if you need crane offload, timed delivery, narrow access vehicles or multiple drops.

Hidden costs to budget for

Do not forget skips, muck-away, membrane, compactor hire, wheelbarrows, delivery charges, access protection, edge restraints and drainage channels. Material quantity is only one part of the finished base/sub-base cost.

Common Base/Sub-base Mistakes

Most failed DIY paving projects do not fail because the top surface was ugly. They fail because the ground preparation was rushed. A thin sub-base on soft soil, an un-compacted layer, trapped water, missing edge restraints or an incorrect material choice can make a new patio or driveway move within months. the working method helps with quantities, but installation quality matters just as much as ordering the right tonnage.

Ordering by guesswork:A few centimetres of depth across a driveway can change the order by tonnes.
Ignoring compaction:Loose aggregate reduces in height when compacted, so the delivery volume and final volume are not the same.
Using rounded pea gravel as a structural base:Rounded gravel can move under load; angular graded stone compacts better.
Skipping edge restraints:Blocks, gravel and slabs can spread sideways if the edges are not restrained.
Not planning drainage:Water trapped in or below the base can soften the ground and accelerate frost damage.
Overbuilding with small bags:25kg bags are convenient, but bulk bags or loose loads are usually better for large areas.

Sub-base Ordering Checklist

Before you place an order, confirm the finished levels, drainage direction, access route and where the material will be tipped or dropped. Aggregates are heavy; moving several tonnes by hand from the kerb to the rear garden can take longer than expected. A small saving on delivery can disappear if the material is left in the wrong place.

Measure the area twice and add a sketch with dimensions.
Confirm compacted depth, bedding depth and finished surface thickness.
Choose dense Type 1 for conventional bases or Type 3/open graded stone for permeable build-ups.
Decide whether you need bulk bags, loose tipped delivery or small bags.
Check lorry access, overhead cables, weak covers, narrow lanes and parking restrictions.
Book a plate compactor or roller before delivery so the material does not sit exposed for days.
Protect drains, inspection covers, air bricks, damp-proof course height and thresholds.
Keep delivery tickets and product descriptions for your project records.

Worked Sub-base Examples for Common UK Jobs

Worked examples make it easier to see how the working method should be used before ordering. The examples below use standard domestic estimating assumptions: compacted depth first, then a loose-to-compacted allowance, then material density. Your supplier may use a different density or bag coverage, so always compare the working method result with the merchant’s product sheet before payment.

Example 1 — 12m² Garden Patio at 100mm Deep

A small patio measuring 4m × 3m has an area of 12m². At 100mm compacted depth, the compacted volume is 1.2m³. With a 15% compaction allowance and 5% ordering allowance, the practical order volume is about 1.45m³. Using MOT Type 1 at roughly 2.0 tonnes/m³, the order weight is close to 2.9 tonnes. That normally means four 850kg bulk bags, or a loose delivery if the supplier offers small loose loads.

Example 2 — 30m² Domestic Driveway at 150mm Deep

A 30m² car driveway at 150mm compacted depth needs 4.5m³ compacted volume. After adding 15% compaction and 5% wastage, the order volume rises to about 5.43m³. At 2.0 tonnes/m³, that is around 10.9 tonnes of Type 1. For this size, loose tipped aggregate or a lorry delivery is usually better value than buying many individual bulk bags, provided there is enough space for tipping and storage.

Example 3 — Permeable Driveway Using Type 3

For a permeable driveway, the sub-base may need to store and move water as well as support vehicles. A 25m² permeable driveway at 200mm depth has a compacted volume of 5.0m³. With allowances, ordering volume might be around 6.0m³. At roughly 1.9 tonnes/m³ for Type 3, the total is around 11.4 tonnes. In this case, drainage design matters as much as quantity because the surface, laying course and base must all work together.

Best ordering habit

Save the working method result, then phone the supplier with the area, depth, material and access details. Ask whether their product is sold as loose tonnes, 800kg bags, 850kg bags or true 1-tonne bags, because the number of bags can change significantly.

Typical Base Build-up for Patios, Driveways and Slabs

A finished paving or concrete build-up is more than just sub-base. A patio might include excavated formation, geotextile membrane, compacted Type 1, bedding mortar, primer slurry and slabs. A block paved driveway usually includes subgrade, geotextile where required, compacted sub-base, sharp sand laying course, blocks, kiln-dried jointing sand and edge restraints. A concrete slab may include compacted hardcore, sand blinding, damp-proof membrane, insulation, reinforcement and concrete.

This matters because the sub-base depth must fit inside the total excavation depth. If you dig only 150mm below finished level and then try to fit 150mm of Type 1 plus 50mm paving plus bedding, the finished surface will be too high. High paving can bridge damp-proof courses, block air bricks, drain water toward the house or create awkward thresholds. Always plan from finished surface level downward, not from the hole upward.

Patio slabs:slab thickness plus bedding mortar plus compacted Type 1 plus optional geotextile.
Block paving:block thickness plus laying course plus compacted Type 1 or permeable equivalent.
Resin driveway:resin layer over suitable asphalt, concrete or open-graded base depending on the system.
Gravel driveway:decorative gravel layer over compacted sub-base, usually with edge restraint and optional gravel grid.
Concrete slab:concrete thickness plus DPM/blinding/insulation details plus compacted hardcore or Type 1.

Where the surface is beside a house, keep drainage and damp-proof course levels in mind. The visible paving should normally fall away from the building, and finished levels should not cover air bricks or create splashback problems. If the base or paving connects to a driveway, dropped kerb, garage threshold or public highway, check local requirements before building.

For structural or adoptable work, follow the project specification

this guide is for general UK estimating. For highways, commercial yards, retaining structures, heavy vehicles, poor ground, building regulations work or warranty-controlled new homes, use the engineer’s specification and relevant standards rather than a generic online estimate.

Base/Sub-base Guide FAQs

Answers to common UK questions about MOT Type 1, Type 3, sub-base depth, tonnage, compaction and ordering aggregate in 2026.

Related UK Building Material Guides

Use these related guides to estimate surrounding materials, delivery quantities and concrete requirements.

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