Gravel Driveway Guide: Sub-Base, Gravel Depth and How Much to Order

A gravel driveway is one of the most affordable and practical surfaces: it drains well, looks good and is easy to top up. But a thin layer of gravel thrown onto bare soil will quickly turn into a muddy, rutted mess. A good gravel drive is built in layers, with a firm sub-base under the stone. Here is how to build one and how much material to order.

The layers of a gravel driveway

1. Compacted ground. Firm, level and falling gently so water runs away.
2. Membrane (optional but common). A permeable geotextile stops the stone sinking into soft ground and helps suppress weeds. It is not part of our aggregates range, so ask your installer or merchant.
3. Compacted sub-base. Around 150mm of MOT Type 1 sub-base bulk bag (800kg) for a drive used by cars, or more on soft ground.
4. Gravel topping. Typically around 40 to 50mm of gravel.

The sub-base is covered in our driveway sub-base guide, so this article concentrates on the gravel.

Choosing the gravel

Gravel size changes how it behaves underfoot and under tyres:

• 20mm gravel is commonly chosen for driveways. The larger stones bind together a little better, are less likely to be kicked out and give a more secure feel under cars. We sell it as a 20mm gravel / shingle bulk bag and a trade pack.
• 10mm gravel is smaller and more comfortable to walk on, so it often suits paths and decorative areas. It is available as a 10mm gravel / shingle bulk bag and a trade pack.

Our listings describe both as construction gravel and shingle, suitable for drainage and concrete as well as general use. Check what you need for the look and feel you want, and call us on 03330 908479 if you would like help choosing.

How deep should the gravel be?

Around 40 to 50mm of gravel is typical. Any thinner and the sub-base or membrane starts to show through, and any deeper makes the surface soft to drive and walk on, because the stones shift under load. A gravel stabilisation grid can help to hold the stone in place on slopes or heavily used drives. It is worth asking your installer whether you need one.

How much gravel do I need?

1. Area in m² = length × width.
2. Volume in m³ = area × depth in metres.
3. Add around 10% for settling and spreading.
4. Multiply by about 1.6 tonnes per m³, a rough loose weight for gravel.
5. Divide by 0.8 for 800kg bulk bags and round up.

Worked example: a 6m × 3m drive with 40mm of gravel

• Area: 18m²
• Volume: 18 × 0.04 = 0.72m³; with 10% allowance 0.79m³
• Weight: about 1.27 tonnes
• Bulk bags: 1.27 ÷ 0.8 = 1.6, so 2 bags of 20mm gravel

For the sub-base under the same drive, 150mm of MOT Type 1 needs about 5.7 tonnes, which is 8 bags. So the whole drive comes to 10 bags. At £48.75 ex VAT per bulk bag at the time of writing, that is £487.50 ex VAT, which is just under our £500 ex VAT free-delivery threshold. At that total, delivery is £25 ex VAT, so adding one more bag would take the order over the threshold. Our guide on working out MOT Type 1 explains the sub-base sum.

Building a gravel driveway step by step

1. Mark out and excavate to the depth of sub-base plus gravel. Allow for the finished level to sit below any damp-proof course.
2. Compact the ground and fix any soft spots with stone.
3. Lay the membrane if you are using one, overlapping the joins.
4. Spread and compact the MOT Type 1 in layers with a plate compactor.
5. Fit edging, such as timber, steel or kerbs, to hold the gravel in. Without edging, stone creeps onto lawns and the road.
6. Spread the gravel evenly with a rake and lightly roll or tamp it.

Maintenance

• Rake the surface now and again to fill ruts and keep the depth even.
• Top up thin patches. Keep a bag of the same gravel in hand so the colour matches.
• Pull weeds early, before roots get established.

Planning and drainage

Gravel is a permeable surface, so it is usually a good option for a front garden in England. For details, see the government guidance on permeable surfacing of front gardens, and check with your local authority if you are in a conservation area or have any other restrictions.

Frequently asked questions

Do I need a sub-base for a gravel driveway?

Yes, if it will carry cars. Gravel on bare soil sinks and rutted tracks form. A compacted sub-base of MOT Type 1 under the gravel keeps the surface firm.

How much gravel per square metre?

At 40mm deep with a 10% allowance, roughly 70kg per m². Work it out for your own depth using the steps above.

Which is better for a driveway, 10mm or 20mm?

20mm is commonly chosen for drives because it stays put better under tyres. 10mm is nicer underfoot and often used for paths.

Will gravel move around?

Some movement is normal. Edging, a stabilisation grid and a sensible depth keep it in check.

Can I use ballast as a topping?

All-in ballast is a mix of sand and stone, so it compacts into a firmer, less decorative surface than clean gravel. It is better as a base or for concrete than as a topping.

Ordering and delivery

You can browse the full range in our cement and aggregates collection. Bulk bags are sold at approximately 800kg each (the packed weight can be up to 850kg depending on moisture), and most sands and gravels are also available in 20 to 25kg trade packs for small jobs. Prices on our website are shown excluding VAT, and VAT is added at checkout.

We deliver to addresses in mainland England only; we do not currently deliver to Wales, Scotland, Northern Ireland or the islands. Timber, aggregates and cement have a minimum order of £250 ex VAT, and delivery is £25 ex VAT on orders under £500 ex VAT and free over £500 ex VAT. Bulk bags are delivered by Moffett lorry (truck-mounted forklift) and offloaded at your site, so someone must be there to receive them and you will need a firm, level area with suitable access. We do not offer next-day delivery. Our shipping policy has the full details, or call us on 03330 908479 or email sales@insulationwarehousedirect.co.uk if you would like a hand working out your order.

The quantities in this guide are estimates. Ground levels, how well the material is compacted and how wet it is all change what you need, and densities vary between quarries, so check the amount with your installer or the manufacturer's guidance before you order. Prices and pack sizes are correct at the time of writing.

Working out quantities? See our MOT Type 1 sub-base guide: how much do I need? or go straight to our aggregates calculator.