How to Lay a Gravel Patio: Depth, Base and Gravel Choice

Key Takeaways

• A gravel patio needs three layers: roughly 100mm of compacted MOT Type 1, a membrane over that, then the decorative gravel at about twice its stone size, so 40mm deep for a 20mm gravel.
• Angular crushed gravel is the optimal choice for a gravel patio because it locks together, while rounded gravel is more likely to roll, sinks and travels in shoes.
• The geotextile membrane in a gravel patio is there to stop the gravel and the sub-base mixing together; nothing stops weeds seeding from above.
• Garden furniture sits level on a gravel patio with a properly compacted base and a thin top layer – adding tiles or flags under the table legs beats any amount of raking.
• A gravel patio against the house must finish at least 150mm below the damp-proof course, per Building Regulations.
• Laying a gravel patio over sound concrete works well, provided the old slab already sheds water and the new level still clears the damp-proof course and the door thresholds.

The worst performing gravel patios usually suffer from the same issues: rounded 10mm gravel straight onto soil; no base; no edging; and usually a table you cannot get level because the legs have settled to a different depth. Two mistakes there, and the expensive one is the one most people don’t see. The wrong stone can be replaced. The missing sub-base means a big job and starting again.

Done properly, a gravel patio drains itself and can be laid over a weekend. This is the build as I do it for clients, including two questions many online guides dodge: which gravel behaves best, and what the membrane is actually there for.

Is a Gravel Patio a Good Idea?

A gravel patio is the cheapest proper seating area you can build, and the right choice if you don’t mind a little raking. They look great, the materials cost a fraction of what flagstones do, there is no cutting and no mortar, and rain disappears through the surface instead of pooling by the back door.

There are some trade-offs, too. Loose stone will slowly drift towards doorways and gates and needs raking back level a few times a year. Plus, thin chair legs will always find the give in gravel. Leaves are the same job on any surface, but the consequence differs: left on flags they are a mess, left in gravel they rot down into the voids and become the compost for weeds to grow in. If you really just want a surface you clean twice a year and ignore, go for flags.

What Is the Best Gravel for a Patio?

Angular crushed gravel in the 14–20mm range is the best choice for a gravel patio, because they lock into a firm surface where rounded stones roll over each other. Rounded gravels are river-worn smooth, which is why they never sit still: every face is a bearing.

Pea gravel, specifically. The soft, tumbled look sells a lot of pea gravel patios and can disappoint many owners. Deep pea gravel walks like dry beach sand, single stones travel indoors in shoes, and chairs sink to the ankles. If you love the look, use it as a thin dressing, and opt for a 20mm or so, over a compacted angular base, and accept the extra upkeep. I am a practical guy, so I would steer you away from it, as a contractor.

The firmer option. Where you want gravel that behaves almost like a solid path, a self-binding gravel carries its own fines and compacts into a surface that barely moves. It looks more parkland than seaside, and it is the answer where wheelchairs or less steady feet matter.

Oh, and if slate chippings are more your thing, the build is the same but the material has its own habits: see the slate chippings laying guide.

How Deep Should a Gravel Patio Be?

A gravel patio needs roughly 150mm of dig: 100mm of compacted sub-base, then gravel at about twice its stone size. For a 20mm gravel that top layer is 40mm; for a 14mm gravel, nearer 30mm. Why 100mm is the number here, and what changes on clay or under a car, is worked through in sub-base depths and quantities.

That twice-the-stone-size rule is the trick most people don’t know, and it is the difference between a patio and a beach. Although most online guides recommend it, go too deep and feet sink instead of skimming across. Racetracks use these gravel traps beside the circuit to swallow a car’s momentum.

One caveat the guides selling you a bulk bag rarely make: on firm, well-drained ground taking nothing heavier than chairs and feet, you can get away without the sub-base. I disagree and it is how a patio ends up in my opening.

How to Lay a Gravel Patio Step by Step

A gravel patio is a very DIY friendly job. They can go down in a day once the digging is done. Just work them in order – failure usually comes from steps skipped, not one done badly.

1. Mark it out, generously. Use a hose or string line, and size it for furniture plus people: I allow at least a metre of clear gravel beyond the table edge, or chairs end up half on the lawn. Check the finished level now: against the house it must sit at least 150mm below the damp-proof course. That is Building Regulations, not a personal choice.
2. Dig to 150mm. Strip turf and topsoil across the whole area. Any ‘soft spot’ you find at the depth should be dug out further and filled with sub-base material, however annoying, because a patch of soft ground left in place will settle later and take the surface down with it.

3. Set the fall as you dig. A patio wants a minimum fall of 1:80 away from the house, which on the ground means dropping 12mm for every metre of run: a four metre patio falls about 50mm end to end. Peg both ends, run a taut string line between them at that drop, and set that line truly level first, using a line level (a small spirit level that hangs on the string itself) or a spirit level on a straightedge. Then, work down the patio dipping from the line with a tape every metre to see where you still need to dig.
4. Fit the edging. Loose stone so the edging goes in before any stone does. A flush timber, steel or brick restraint in a narrow trench is enough; it needs to restrain, not stand proud. The options are covered in the gravel edging guide.

5. Build the sub-base. I use MOT Type 1, spread it and compact it hard to a minimum of 100mm, with a wacker plate. I reckon around eight passes, up and down then side to side, half-lapping each pass, until the plate stops sinking and starts to skip. As a guide, to get the 100mm compacted depth, it would require around 130 to 140mm of loose material. Next, measure from your string line every metre across the whole area, and anything more than about 15mm off gets more material and another pass, not a shrug. Only other ‘Basers’ ever admire a sub-base, yet it is the only layer you can’t fix later without re-doing the whole patio. For the build itself, layer by layer, see how to lay a sub-base.
6. Lay the membrane over the compacted base. Between base and gravel to stop them mixing, overlapping joints by 10cm. Pin it every 45cm or so, and run the sheet up the trench sides so the edging traps it. Now here’s a quick test for your fall if you’re not sure: run a hose on it and watch where the water goes. If any of it sits or tracks the wrong way, the sheet rolls back and you fix the base underneath. Do this and any correction will only take fifteen minutes, instead of hours, later. PRO TIP: If you are working with particularly soft ground or heavy clay, I would add a second sheet at the bottom before the Type 1 goes in, and would probably add an extra 5 cm of compacted sub-base. Ground like that cannot be relied upon to hold a base up under the weight of heavy furniture and traffic, but it’s just an extra pre-cautionary step that will cost you a lot less at the time then it will in the future if things don’t work out.

7. Spread the gravel. Barrow it into small piles around and spread with the back of a rake to twice the stone size height, no deeper. I always tell clients to order a little bit more and keep it on hand because every gravel patio thins slightly in its first year as it beds in.
8. Wash it off. Bulk-bag gravel arrives dusty. A going-over with the hose brings the true colour up.
9. Upkeep. What keeps a gravel patio clean is a quick, boring routine: a monthly rake through, leaves shifted before they rot down, seedlings pulled while still rootless. Ten minutes with a spring-tine rake or gentle leaf-blower can’t be beaten.

Can You Lay a Gravel Patio Over Concrete or Old Slabs?

Laying a gravel patio over an existing concrete pad works well, provided the slab sheds water and the raised level still clears the damp-proof course and the door thresholds. The concrete becomes your sub-base, compacted better than any wacker plate will manage, and you skip the dig.

Three checks before you start:

1. Watch the slab in rain or hose it to check: gravel hides a puddle, it does not cure one, so a pad that ponds now needs its low spot addressed or the slab lifting;
2. Run a heavy-duty weed membrane over cracked or jointed concrete; weeds grow out of cracks where windblown seed settles, and the sheet blanks those off, and what to put under gravel covers which grade to buy; and,
3. Keep the gravel at twice its stone size with an edge restraint at the perimeter, or the lawn will swallow it.

Can You Put Garden Furniture on a Gravel Patio?

In my experience, garden furniture can definitely sit level on a gravel patio, as long as it has a compacted base and a thin top layer. When you have deep, loose gravel, every leg digs its own divot.

Two easy upgrades to make it more durable: set a flagstone flush into the gravel under each table leg, which will be invisible once the stone is raked over, and furniture with broad feet or sled-style legs rather than thin spikes.

For a fire pit, gravel is one of the best surfaces there is, since stray sparks meet stone rather than decking; I advise clients to stand the pit on a couple of flags anyway, so the ash sweeps up instead of working down between the stones.

Next Steps

We stock angular gravels in the 14–20mm range, MOT Type 1 by the bulk bag and heavy-duty membrane, and the site’s gravel calculator sizes the order before you spend a pound. Order samples first if colour matters. Build the base right, keep the gravel thin, and it won’t end up a gravel trap.

If you would rather talk your gravel patio through with a person, ring Outdoor Aggregates on 0330 043 7585. The office is open 7am to 7pm, seven days a week.

Have you ever laid a gravel patio? What did you build it over, and how does it feel underfoot once the furniture is on it? Love to hear about it in the comments.

FAQs

Is gravel cheaper than paving slabs?

A gravel patio comes in well under a flagged patio of the same size, because the material costs less and the labour is yours for a weekend rather than a contractor’s for a week.

What do you put under a gravel patio?

Under a gravel patio you put 100mm of compacted MOT Type 1 and a separation membrane; the membrane keeps the layers apart and does nothing about weeds arriving from above. That second half is the part the packaging never says. Weeds in a gravel patio nearly all start as windblown seed germinating in the dust and leaf litter between the stones, growing down, not up. No sheet at any depth prevents that, and no sheet improves drainage either: the best a membrane manages is not getting in the way. Soft or heavy clay ground is the one case for two sheets, the second at the bottom of the dig, holding the sub-base out of the mud. For the fuller argument on membranes, grades and what genuinely belongs under loose stone, see what to put under gravel.

Can I just lay gravel on soil?

Gravel laid straight onto soil never makes a lasting gravel patio; the stones tread in within a season, the soil comes up between them, and the surface never sits level again. The 100mm of compacted base is what you are actually standing on.

Can you put garden furniture on a gravel patio?

Garden furniture sits level on a gravel patio when the base is compacted and the top layer stays thin; on deep loose gravel every leg digs its own divot. A flag set flush under each pair of table legs, hidden once the stone is raked over, ends the wobble for good.

Can you put a fire pit on a gravel patio?

A fire pit sits safely on a gravel patio, because stray sparks land on stone rather than timber. I advise clients to stand the pit on a couple of flags so the ash sweeps up instead of working down between the stones.

How much gravel do I need for a patio?

A gravel patio takes its depth from the stone size, roughly double it, so a 20mm gravel wants about 40mm across the whole area. Measure length and width, and the site’s gravel calculator turns those numbers into bags.

Does a gravel patio need drainage?

A gravel patio drains through its own surface, so it needs no added drainage on ground that soaks water away already. Standing water in the lawn around it is a garden drainage problem, best solved before you build.