Driveway preparation

Driveway sub-base preparation: what should happen below the surface?

The visible finish gets the attention, but excavation, sub-base, compaction, edging and drainage decide whether a driveway stays level. Use this guide to compare written specifications before choosing a surface.

Updated 19 July 2026Oxfordshire · Berkshire · Thames Valley

RKG's existing service and quote pages repeatedly mention the same foundations: ground conditions, excavation, MOT Type 1, compaction, edging, drainage and access. Those details are not cosmetic extras. They are the parts that support the driveway after the installers leave.

Quick answer

A durable driveway needs the existing surface or soil assessed, excavation to suitable ground, a correctly specified sub-base, firm edge restraints, planned drainage and compaction before the chosen finish goes down. The exact build-up changes by surface and site conditions, so it should be written into the quote.

RKG's tarmac page gives one concrete example: 200–300mm excavation to firm subgrade, heavy-duty membrane, then 150mm MOT Type 1 compacted in 75mm lifts before the binder and surface courses.

What preparation details should appear in a quote?

Preparation itemWhy it mattersWhat to ask
Existing surface and excavationOld concrete, tarmac, lawn or failed paving can change waste removal, depth and labour.What is being removed, and how deep will the dig-out be?
Sub-base materialThe sub-base carries vehicle loads and helps the surface stay level.Is compacted MOT Type 1 or another specified base included?
Compaction and layersA shallow or poorly compacted base can sink, rut or crack under regular use.Will the base be compacted in layers, and does depth suit the surface?
Membrane or geotextileSome specifications use a membrane to separate the base from the subgrade or support shingle installs.Is a membrane needed for this ground and surface?
Edging and restraintsEdges help stop tarmac cracking, resin movement, block spread and shingle migration.What kerbs, borders, hidden edging or restraints are included?
Drainage and fallsWater should not be sent toward the house, garage or public highway without a suitable route.Where will water drain, and is a permeable surface or channel needed?

How preparation changes by surface

Tarmac

RKG's tarmac page is the clearest published build-up: dig down to firm subgrade, grade falls to drainage, use heavy-duty membrane, lay 150mm MOT Type 1 in 75mm lifts, restrain the edges, then install binder and surface courses. It also notes that a fully engineered sub-base helps a hot-rolled tarmac driveway last 15–20 years before resurfacing.

Block paving

Block paving needs a stable foundation plus restrained borders, patterns, cuts and jointing. RKG's quote checklist recommends asking about excavation depth, sub-base type, compaction and edging because those hidden details can make two block paving quotes very different.

Resin bound

Resin is described across the site as a premium, smooth and SuDS-friendly surface when correctly specified. The base still has to be suitable before the resin finish is laid, and drainage/permeability should be confirmed in the written quote rather than assumed.

Shingle and gravel

RKG's service copy references shingle over membrane and edging, with optional stabilising grids in guide content. Preparation is usually quicker than some surfaces, but weak edges or missing stabilisation can let loose stone move into lawns, drains or the road.

Red flags when comparing quotes

What to read next

Use the driveway quote checklist to compare written specifications, then read the planning and drainage guide if water run-off is a concern. For surface-specific preparation, compare tarmac driveways, resin bound driveways, block paving and shingle driveways.

Sub-base FAQs

Common driveway preparation questions

What is a driveway sub-base?
The sub-base is the compacted foundation below the visible driveway surface. RKG's site references engineered sub-bases, compacted MOT Type 1, excavation depth, membranes, edging and drainage as quote-stage checks that affect long-term performance.
How deep should a driveway be excavated?
Depth depends on the existing ground, surface choice and vehicle use. RKG's tarmac page describes a 200–300mm dig down to firm subgrade and 150mm MOT Type 1 in 75mm lifts for tarmac, while other surfaces use their own preparation requirements.
Why do edging and drainage matter before the surface is laid?
Edges keep the finished surface restrained, and drainage controls where water goes. RKG's guidance repeatedly links edging, falls, permeable areas, channel drains and ground conditions with a durable driveway specification.
Get a free quote

Make sure the hidden build-up is specified before work starts.

Book a free site visit and RKG will confirm ground conditions, drainage, edging and surface preparation in writing.