What Is a Sub-Base? Plain‑English Guide
A sub-base is the compacted stone layer that carries the load of your patio or driveway. It spreads weight, limits settlement and movement, allows water to escape, and reduces frost heave. Get this layer right and your surface will last for years.
A typical build-up is: existing soil (subgrade), geotextile (on soft ground), sub-base, laying course, then your finish (flags, block paving, gravel, tarmac, or resin). The aggregate you choose affects strength, drainage and lifespan. As local builders’ merchants, A R Richards can supply the right aggregates and practical advice. Learn more on our about us page. We deliver across Shropshire, Staffordshire, Cheshire and the wider Midlands.
MOT Type 1 vs 6F2 vs 6F5 vs Scalpings — Quick Comparison
- MOT Type 1 (40mm down to dust): Dense, high strength, tighter drainage. Best for patios and block‑paved drives. Smooth to level. Typical depths: 75–100mm patios; 150–200mm drives.
- 6F2 (recycled, 75mm down): Coarser, angular, ideal for capping soft or made‑up ground. Great value for bulk fill. Always top with 50–100mm Type 1 before paving.
- 6F5 (well‑graded, 75mm down): Similar size to 6F2 but more consistent. Strong base for heavy‑duty jobs and access roads. Blind with Type 1 for fine finishes.
- Scalpings (often 40mm limestone): Economical, compacts well. Good for paths and gravel drives. Tighter drainage than single‑size stone.
Layering tip: On weak ground, use 150–300mm of 6F2/6F5 first, then 50–100mm of Type 1 for a smooth, tight finish. For drainage ideas, see our guide to effective drainage systems and how we produce quality recycled aggregates in crushing 6F2.
MOT Type 1 — Best Sub‑Base for Patios and Block‑Paved Drives
MOT Type 1 is a well‑graded limestone or granite from 40mm down to dust. It compacts into a dense, strong layer that’s ideal under patios and block paving. Because drainage is tighter, set falls to drains or edges to shed water.
Pros: smooth finish, stable edges, easy to level. Cons: not ideal on very wet sites without drainage. Practical tips: lightly moisten before compacting, lay in 75mm layers, compact with a wacker plate or roller, and install solid edge restraints. For quantities, try our aggregates calculator. For permeable block paving, consider a free‑draining sub‑base (e.g. Type 3) as specified.
This image was generated with AI and may not always represent the product or service exactly.
6F2 — Tough Capping for Soft or Made‑Up Ground
6F2 is a recycled crushed mix (typically concrete, brick and hardcore) graded to around 75mm down. Its angular particles interlock well, making it excellent as a capping layer to bridge soft or variable subgrades and to build levels cost‑effectively.
Drainage is moderate; initial voids reduce as fines settle. For patios and block paving, always add 50–100mm of Type 1 on top for a smooth, tight finish. Compact 6F2 in thicker layers with a roller where possible. If you’re digging out, we can collect spoil with our muck away service. Ask about our in‑house recycling and crushing.
6F5 — Stable, Well‑Graded Hardcore for Heavy‑Duty Jobs
6F5 is a consistent, often better‑screened 75mm down aggregate that’s ideal for new drive build‑ups, heavy vehicles, and temporary access roads. Its grading improves stability and compaction compared with very mixed hardcore.
For patios, flags or blocks, add a Type 1 or 20mm down blinding layer to achieve a fine finish. Compact in 100–150mm layers. Use string lines or a laser level to keep falls and thickness accurate.
Scalpings — Economical Base for Paths and Gravel Drives
Scalpings usually means a 40mm down limestone scalp. They compact well and suit paths and gravel drives where the subgrade is already firm.
They are tighter and less free‑draining than single‑size stone. Avoid using road planings beneath paving unless specified; tar‑bound planings can be hazardous and require proper testing, handling and disposal routes.
Depth Guide — Build‑Ups That Last
- Patios on firm ground: 75–100mm Type 1, compacted in two layers.
- Block‑paved and paved drives (cars): 150–200mm Type 1 in layers.
- Poor ground, clay or vans: 150–300mm 6F2/6F5 capping plus 50–100mm Type 1.
Use a geotextile separator on weak or silty soils to stop fines pumping into the stone. Compact each layer thoroughly. Set falls away from buildings and keep the final surface at least 150mm below the DPC. Good edge restraints prevent spread and keep lines straight.
This image was generated with AI and may not always represent the product or service exactly.
Drainage, Frost and SuDS Rules in the UK
Type 1 is dense and tends to shed water; 6F2/6F5 are coarser but still include fines. On wet sites, add drains or consider permeable systems to avoid standing water. Frost protection improves when water can escape and the sub‑base is well compacted.
In England, front garden drives over 5m² must be permeable or drain to a soakaway to remain permitted development. If water is trapped, fines can pump and the surface will rut. Our blog on understanding effective drainage systems explains the options and SuDS principles in plain English.
Simple Calculators — Work Out Volumes and Tonnes
Measure area and depth in metres. Volume (m³) = length × width × depth. Typical loose bulk densities (guide only): Type 1 ≈ 2.2 t/m³, 6F2/6F5 ≈ 1.9 t/m³, scalpings ≈ 2.0 t/m³.
- Example patio: 5.0m × 3.0m × 0.10m = 1.50m³ of Type 1 ≈ 3.3 tonnes.
- Example drive: 10.0m × 3.0m × 0.20m = 6.00m³ of Type 1 ≈ 13.2 tonnes.
Add around 10% for compaction, trimming and level changes. For a quick total, use our aggregates calculator. Smaller jobs? Ask about bagged products from our merchants team.
Ordering and Delivery — Avoid Delays and Re‑Handles
Loose tip is best value if you have access and a clear tipping area. Bulk bags suit tight sites and keep things tidy. Check lorry width, height, turning space and overhead cables. Book early during peak periods.
Plan spoil removal at the same time. Use skips for smaller digs and muck‑away for larger volumes. Ordering plant, aggregates and waste from one provider keeps the job moving and reduces downtime on site.
Real‑World Build‑Ups From Our Yard Team
New patio on clay: lay a geotextile, then 150mm of 6F5, 75mm of Type 1, then your sharp‑sand laying course. Compact each layer.
Gravel driveway upgrade: on firm ground use 150–200mm of Type 1 (or scalpings), with edging to hold stone and a geotextile to separate fines.
Farm track or building plot access: 200–300mm of 6F2/6F5, topped with 50mm of Type 1 or planings where specified and compliant. Maintain with periodic top‑ups.
Sustainability, Recycling and Quality You Can Trust
Recycled 6F2 and 6F5 from A R Richards cut cost and carbon while meeting recognised quality expectations such as WRAP protocols. We crush, screen and test to deliver consistent material.
Tar‑bound planings and suspect wastes need proper testing and licensed handling. With in‑house recycling and a modern fleet, we supply quickly and responsibly across our region.
Get a Fast Quote and Local Delivery
Ready to order? Speak to our merchants team for practical advice and fast local delivery. We supply across Shropshire, Staffordshire, Cheshire and the Midlands with reliable, family‑run service.
Next steps: choose your material, measure the area, run the calculator, confirm loose tip or bags, and plan waste removal. For help now, contact us.
FAQs
What sub-base should I use under block paving?
MOT Type 1. Lay 150–200mm on drives, compacted in layers, with solid edge restraint and falls to drains.
Can I use 6F2 or 6F5 on their own for a patio?
Use them as capping on weak ground, then top with 50–100mm of Type 1 for a smooth, tight finish.
Do I need a geotextile membrane?
Yes on soft, clay or made‑up ground to separate soil from stone and stop fines pumping into the sub‑base.
How wet can the sub-base be before compaction?
Slightly damp is ideal. If it’s saturated, let it drain or dry first to avoid pumping and loss of strength.
What depth of sub-base do I need for a car drive?
150–200mm of Type 1 on firm ground. On weak ground, add 150–300mm of 6F2/6F5 capping first.
Do you deliver bulk bags and loose tipped?
Yes. Choose bulk bags for tidy, tight sites, or loose tip for best value where access allows.
Will scalpings work under a gravel drive?
Yes on firm subgrade. They compact well and hold the gravel, but are less free‑draining than single‑size stone.
