Base Sub-Base Calculator 2026 | Road & Driveway Foundation Calculator

Base Sub-Base Calculator 2026

Road, Driveway & Car Park Foundation Calculator

Calculate Aggregate Material Requirements

The Base Sub-Base Calculator helps calculate the volume and weight of aggregate materials required for road foundations, driveways, car parks, and hardstanding areas in 2026. Base and sub-base layers provide structural support, load distribution, and drainage beneath paved surfaces according to MCHW (Manual of Contract Documents for Highway Works) specifications.

Our calculator determines quantities for Type 1 MOT, Type 2 MOT, crusher run, and other granular materials complying with British Standards. Accurate base and sub-base calculations prevent settlement, surface cracking, and premature pavement failure while optimizing material costs.

🛣️ Base Sub-Base Calculator

Calculate aggregate material requirements

Project Dimensions

Length (meters)

Width (meters)

Layer Specifications

Sub-Base Depth (mm)

Base Depth (mm)

Sub-Base Material

Base Material

Wastage Allowance (%)

Base and Sub-Base Materials Guide 2026

Base and sub-base layers are granular materials placed beneath paved surfaces to provide structural support, distribute traffic loads, and facilitate drainage. UK highway specifications define material types, gradations, and performance requirements for different applications.

✅ Key Functions of Base Sub-Base:

Load Distribution: Spreads traffic loads from surface to subgrade, preventing concentrated stresses
Structural Support: Provides bearing capacity and resistance to deformation under repeated loading
Drainage Layer: Allows water to drain horizontally, protecting subgrade from saturation
Frost Protection: Non-frost susceptible materials prevent frost heave damage in winter
Working Platform: Provides stable construction surface for paving operations
Thickness Optimization: Proper design reduces overall pavement thickness and cost

MOT Type 1 vs Type 2 Sub-Base Materials

Material Type	Specification	Density	Typical Use	Cost 2026
Type 1 MOT	Clause 803 (0-40mm)	1.8 t/m³	Roads, car parks, heavy traffic	£25-35/tonne
Type 2 MOT	Clause 804 (0-63mm)	1.9 t/m³	Sub-base, bulk fill, light traffic	£20-28/tonne
6F2 Crushed Rock	Table 6/1 (0-40mm)	1.85 t/m³	General purpose sub-base	£22-30/tonne
6F5 Recycled	Table 6/3 (0-75mm)	1.75 t/m³	Sustainable option, lower cost	£15-22/tonne
Crusher Run	Varies (0-50mm)	2.0 t/m³	Base layer, driveways	£24-32/tonne
Dolomite	High strength (0-40mm)	2.1 t/m³	Heavy duty base	£28-38/tonne
Granite	Premium (0-40mm)	2.2 t/m³	Highways, industrial	£30-42/tonne
Limestone	Standard (0-40mm)	2.0 t/m³	General applications	£23-31/tonne

Type 1 MOT

Specification Clause 803

Density 1.8 t/m³

Cost 2026 £25-35/tonne

Type 2 MOT

Specification Clause 804

Density 1.9 t/m³

Cost 2026 £20-28/tonne

6F5 Recycled

Specification Table 6/3

Density 1.75 t/m³

Cost 2026 £15-22/tonne

Granite

Specification Premium

Density 2.2 t/m³

Cost 2026 £30-42/tonne

Recommended Base Sub-Base Thickness Specifications

Layer thickness depends on traffic loading, subgrade strength (CBR value), and pavement design. Domestic driveways require thinner sections than highways or commercial car parks. The Design Manual for Roads and Bridges (DMRB) provides detailed pavement design guidance.

Domestic Driveway

Sub-Base: 100-150mm Type 1 MOT

Base: Not always required

Surface: 50-60mm tarmac or 50mm block paving

Total Depth: 150-210mm

Traffic: Light domestic vehicles only

Heavy Duty Driveway

Sub-Base: 150-200mm Type 1 MOT

Base: 75-100mm crusher run

Surface: 60-75mm tarmac or 60mm paving

Total Depth: 285-375mm

Traffic: HGVs, commercial vehicles

Car Park (Light Use)

Sub-Base: 150-200mm Type 1 MOT

Base: 100mm dense bitumen macadam

Surface: 40-50mm wearing course

Total Depth: 290-350mm

Design Life: 15-20 years

Car Park (Heavy Use)

Sub-Base: 225-300mm Type 1 MOT

Base: 150mm dense bitumen macadam

Surface: 60mm wearing course

Total Depth: 435-510mm

Design Life: 20-30 years

Access Road (Residential)

Sub-Base: 200mm Type 1 MOT

Roadbase: 120mm DBM

Binder + Surface: 40+30mm

Total Depth: 390mm

Standard: Local authority adoptable

Main Highway (Flexible)

Sub-Base: 250-350mm Type 1 MOT

Roadbase: 200-250mm DBM

Binder + Surface: 60+40mm

Total Depth: 550-700mm

Design: Full DMRB compliance

Industrial Hardstanding

Sub-Base: 250-350mm Type 1 MOT

Base: 150-200mm crusher run

Surface: 75-100mm concrete slab

Total Depth: 475-650mm

Loading: Forklifts, heavy plant

Pedestrian/Cycle Path

Sub-Base: 75-100mm Type 2 MOT

Base: Not required

Surface: 40mm tarmac or 50mm paving

Total Depth: 115-150mm

Loading: Pedestrian and cycle only

Installation Process for Base Sub-Base Calculator

Proper installation ensures pavement longevity and performance. Each layer must be placed, graded, and compacted to specification. Poor installation leads to settlement, rutting, and premature failure regardless of material quality.

📋 Installation Steps:

Step 1 - Site Preparation: Remove topsoil, vegetation, and organic materials. Excavate to required depth (typically 250-400mm for driveways)
Step 2 - Subgrade Preparation: Compact natural ground to 95% maximum dry density. Level and grade to achieve proper drainage falls (minimum 1:40)
Step 3 - Geotextile Membrane: Install separation membrane on weak subgrades (CBR<5%) to prevent migration of fine particles into aggregate
Step 4 - Sub-Base Layer: Place Type 1 MOT in maximum 150mm layers. Compact each layer to 95% relative compaction using vibrating roller or wacker plate
Step 5 - Base Layer: Install base course material in 100-150mm layers. Achieve 98% compaction. Check levels and crossfalls match design
Step 6 - Edge Restraints: Install kerbs, edgings, or haunching before surfacing to prevent lateral movement of pavement structure
Step 7 - Surface Course: Apply final wearing surface (tarmac, block paving, or concrete) according to manufacturer specifications

Compaction Requirements and Testing

Adequate compaction is critical for pavement performance. Under-compacted layers settle under traffic, causing surface deformation. Testing verifies compaction meets specification requirements.

Compaction Equipment

Vibrating Plate: Suitable for areas up to 50m², domestic driveways. 100-200kg models

Pedestrian Roller: 500-750kg single drum. Small to medium car parks

Ride-On Roller: 1.5-3 tonne tandem. Highway works, large areas

Sheep's Foot Roller: Cohesive soils and clay subgrades

Compaction Standards 2026

Subgrade: 95% max dry density (MDD) BS 1377 test

Sub-Base: 95% relative compaction per BS 1377

Base Course: 98% relative compaction

Layer Thickness: Maximum 150mm uncompacted per layer

Passes: Typically 4-6 passes with vibrating roller

Field Testing Methods

Sand Replacement: BS 1377 Part 2 - measures in-situ density

Nuclear Density: Quick non-destructive testing (specialist equipment)

Plate Bearing: Measures stiffness and bearing capacity

Proof Rolling: Visual check using loaded vehicle

Common Compaction Issues

Over-Compaction: Particle crushing, grading breakdown

Under-Compaction: Settlements, ruts, surface cracking

Moisture Content: Too wet or dry reduces compaction efficiency

Layer Thickness: Layers over 150mm don't compact properly at depth

Drainage and Crossfall Design

Effective drainage prevents water accumulation in pavement layers, which causes accelerated deterioration, frost damage, and reduced bearing capacity. Proper crossfall design sheds surface water quickly.

⚠️ Drainage Design Requirements:

Minimum Crossfall: 1:40 (2.5%) for tarmac surfaces, 1:60 for concrete
Longitudinal Fall: Minimum 1:80 along pavement length
Edge Drains: Required where pavement drains toward boundaries or structures
Permeable Materials: Type 1 MOT allows horizontal drainage through sub-base
Soakaways: Must be 5m from buildings, minimum 1m deep below base level
Gullies: Maximum 200m² catchment per gully on impermeable surfaces
Membrane Protection: Prevent waterlogging of subgrade using geotextiles on clay

CBR Testing and Subgrade Strength

California Bearing Ratio (CBR) measures subgrade strength and determines required pavement thickness. Higher CBR values allow thinner pavement sections. Standard test methods follow BS 1377-4 protocols.

CBR Values and Design Implications

Soil Type	Typical CBR	Sub-Base Thickness	Subgrade Treatment
Soft Clay / Peat	< 2%	400-600mm+	Excavate and replace, stabilization, geogrid
Firm Clay	2-5%	300-400mm	Geotextile separation, lime stabilization
Stiff Clay	5-8%	250-300mm	Geotextile recommended, drainage control
Sandy Clay	8-15%	200-250mm	Standard preparation, compaction only
Sand / Gravel	15-30%	150-200mm	Excellent subgrade, minimal treatment
Dense Sand/Gravel	30-50%	100-150mm	High quality subgrade
Crushed Rock	> 50%	75-100mm minimum	Exceptional conditions

Soft Clay / Peat (CBR < 2%)

Sub-Base Thickness 400-600mm+

Treatment Excavate & replace

Firm Clay (CBR 2-5%)

Sub-Base Thickness 300-400mm

Treatment Geotextile, lime

Sandy Clay (CBR 8-15%)

Sub-Base Thickness 200-250mm

Treatment Standard prep

Sand/Gravel (CBR 15-30%)

Sub-Base Thickness 150-200mm

Treatment Minimal required

Cost Estimation for Base Sub-Base Projects 2026

Material costs vary by region, quantity ordered, delivery distance, and current market conditions. Labour and equipment costs add significantly to total project expense. Obtaining multiple quotes ensures competitive pricing.

Material Costs (Delivered)

Type 1 MOT: £25-35/tonne delivered

Type 2 MOT: £20-28/tonne delivered

6F5 Recycled: £15-22/tonne delivered

Crusher Run: £24-32/tonne delivered

Delivery: £50-150 per load (15-20 tonnes)

Equipment Hire 2026

Wacker Plate: £35-50/day

Small Roller: £65-90/day

Large Roller: £120-180/day

Mini Digger: £80-120/day

Dumper: £60-85/day

Weekly rates: Typically 4× daily rate

Labour Costs

Groundworker: £180-250/day

Labourer: £120-160/day

Plant Operator: £200-280/day

Small Driveway: 2-3 days (2 workers)

Large Project: Pro rata rates apply

Weekend/Night: Premium rates 1.5-2×

Total Project Costs

Domestic Driveway (50m²): £1,800-3,200

Large Driveway (100m²): £3,200-5,500

Car Park (500m²): £15,000-28,000

Access Road (per m): £80-150/linear metre

Includes: Materials, labour, equipment, disposal

Base Sub-Base Calculator FAQs

What is the difference between base and sub-base?

Sub-base is the lower layer placed directly on prepared subgrade (natural ground), typically Type 1 or Type 2 MOT aggregate 100-300mm thick. Base (or roadbase) is the upper structural layer, often stronger material like crusher run or dense bitumen macadam, placed on sub-base before the surface course. Sub-base provides bulk support and drainage; base provides higher strength closer to traffic loads.

How much Type 1 MOT do I need for a driveway?

For a standard domestic driveway, use 150mm (0.15m) depth of Type 1 MOT. Calculate volume: Length × Width × 0.15 = volume in m³. Add 10% wastage. Type 1 weighs approximately 1.8 tonnes/m³, so multiply volume by 1.8 for tonnage. Example: 10m × 5m × 0.15 = 7.5m³ × 1.8 = 13.5 tonnes needed. Order 15 tonnes allowing wastage.

What depth of sub-base do I need?

Depth depends on traffic loading and ground conditions (CBR). Typical depths: pedestrian paths 75-100mm, domestic driveways 150mm, heavy driveways/light commercial 200mm, car parks 200-300mm, highways 250-350mm. Poor ground (low CBR) requires thicker sections or ground improvement. Building control or highway specifications dictate minimum depths for adoptable roads.

Can I use Type 2 instead of Type 1 MOT?

Type 2 MOT is suitable for sub-base layers in light-duty applications like domestic driveways and paths. Type 1 is preferred for higher loading (commercial driveways, car parks, roads) due to better grading and compaction properties. Type 1 costs £5-7/tonne more but provides superior performance. Never use Type 2 for base layers or heavy traffic applications.

How many tonnes are in a bulk bag of MOT?

Standard bulk bags (also called jumbo bags or ton bags) contain approximately 0.85-1.0 tonnes of Type 1 MOT. Exact weight varies by supplier and moisture content. One bulk bag covers roughly 4-5m² at 100mm depth. Bulk bags cost more per tonne (£40-60/bag) than loose loads but suit small projects without lorry access. Loose tipped loads are more economical for areas over 20m².

Do I need membrane under MOT Type 1?

Geotextile membrane (terram) is essential on weak subgrades (CBR < 5%), clay soils, or where fine particles might migrate into aggregate. Membrane prevents mixing of subgrade and aggregate, maintains drainage properties, and reduces required thickness. Not always necessary on good quality sand/gravel subgrades (CBR > 15%). Cost: £1-2/m² for geotextile is cheap insurance against future problems.

How do you compact Type 1 MOT properly?

Place Type 1 in layers maximum 150mm uncompacted thickness. Compact each layer with vibrating plate compactor (domestic) or vibrating roller (commercial) making 4-6 passes. Check material is at optimum moisture content - slightly damp compacts best. Over-dry material won't compact; saturated material becomes unstable. Achieve 95% relative compaction measured by sand replacement or nuclear density tests. Final surface should be firm with no visible movement.

What is CBR and why does it matter?

California Bearing Ratio (CBR) measures subgrade strength as percentage of standard crushed rock (100% CBR). Soft clay might be 2% CBR; good sand/gravel 20-30% CBR. Low CBR requires thicker pavement or ground improvement. CBR testing (BS 1377-4) involves pushing steel plunger into soil sample and measuring resistance. Professional ground investigation determines CBR for pavement design. Assuming CBR without testing risks under-design and premature failure.

Can I lay tarmac directly on Type 1 MOT?

For domestic driveways, tarmac can be laid directly on well-compacted Type 1 MOT sub-base. Use minimum 60mm tarmac thickness (two layers preferred: 40mm binder + 20mm surface). Commercial applications require separate base course (100-150mm dense bitumen macadam) between sub-base and surface. Proper compaction of Type 1 to 95%+ is critical - inadequate compaction causes surface settlement and cracking within 1-2 years.

How long does base sub-base installation take?

Timeline depends on size and access. Small domestic driveway (50m²): 2-3 days for excavation, sub-base, and compaction. Large driveway (100m²): 4-5 days. Car park (500m²): 2-3 weeks. Poor ground conditions, wet weather, or difficult access extend duration. Allow extra time for material deliveries, equipment mobilization, and inspection approvals. Proper curing time (24-48 hours) needed after compaction before trafficking or applying surface course.