For most small and medium garden sheds, a properly prepared gravel shed base is the lowest-cost, best-draining foundation you can build yourself. The key conditions: use clean, angular crushed stone of appropriate size compacted to a suitable depth, and always fit a rigid perimeter to contain it. Without that edging, the stone migrates, the base loses level, and the shed tilts.
Your first action before ordering anything is to check ground firmness. Push a steel rod or a screwdriver into the soil. If it sinks easily past 150 mm, you are on soft or boggy ground, and a gravel base alone will not hold. On firm soil, a gravel base is generally sufficient.
Key takeaways
A gravel shed base works reliably for small and medium UK garden sheds when you use angular 20 mm crushed stone, compact it to a recommended depth between 7 and 10 cm for small to medium sheds (deeper for heavier or larger structures), and fit a rigid perimeter to contain it.
| Point | Details |
|---|---|
| Stone specification | Use 20 mm angular crushed stone; add MOT Type 1 sub-base on soft or clay ground. |
| Compacted depth | Aim for a recommended depth between 7 and 10 cm of compacted gravel; compact in lifts, not all at once. |
| Rigid perimeter is non-negotiable | Uncontained gravel migrates and loses level; always fit timber or plastic edging. |
| Pad size | Extend the pad 150–300 mm beyond the shed footprint on all sides. |
| When to choose concrete | Choose a concrete slab for heavy summerhouses, log cabins, or boggy ground. |
| Poweraggregates | Supplies 20 mm crushed stone, MOT Type 1, pea shingle and bagged options with nationwide delivery. |
Table of Contents
- What is a gravel shed base and when should you use one?
- Pros and cons of a gravel shed base
- Choosing the right stone: what works and what to avoid
- What to check before you start: site, permissions and drainage
- How to calculate how much gravel you need
- Step-by-step: laying a gravel shed base
- How to pair a gravel base with common shed floor systems
- Maintenance, likely problems and how to fix them
- Supplier-backed tips from Poweraggregates: what to ask and watch for
- The mistake almost every DIYer makes
- Ready to order your materials? Poweraggregates has everything you need
- Sources
- FAQ
What is a gravel shed base and when should you use one?
A gravel shed base is a compacted pad of free-draining stone, typically a moderate depth suitable for drainage and stability, that sits directly on prepared subsoil. The terms “gravel base”, “gravel foundation” and “gravel pad” all refer to the same thing: a level, permeable platform that keeps the shed floor lifted clear of standing water.
Summerhouse24’s guide to gravel shed bases confirms that a correctly built gravel base drains well, prevents water pooling beneath the shed, and reduces timber rot — a genuine advantage in the UK’s wet climate.
Best suited for:
- Small and medium timber or plastic sheds (roughly up to 10 × 8 ft)
- Gardens with clay or poorly draining soil where a concrete slab would trap water
- Temporary or removable structures where you may want to relocate the shed later
- DIYers who want a weekend project without hiring a groundworker
When to choose something else:
- Very soft, boggy or waterlogged ground — a reinforced concrete slab or piled base is safer
- Heavy summerhouses, log cabins or garden rooms over roughly 2.5 tonnes
- Sites where local planning rules require a rigid, permanent foundation
- Sloping ground with more than about 150 mm of fall across the pad (manageable, but needs careful edging and possibly a stepped sub-base)
Pros and cons of a gravel shed base
Advantages:
- Excellent drainage — water passes straight through rather than pooling, which is the primary reason a gravel foundation for a shed outperforms concrete in wet UK gardens
- Lower cost than a concrete slab for most shed sizes
- Straightforward DIY build with standard tools and a hired plate compactor
- Adjustable and removable if you change your mind about shed placement
- Forgiving on slightly uneven ground — you can re-level by raking and recompacting
Disadvantages:
- Stone migrates without a rigid perimeter; Buy Sheds Direct is clear that clean stone lacking fines will shift under localised loads unless contained
- Requires periodic maintenance: re-topping, re-levelling and weed control
- Not rigid enough alone for very heavy structures
- Weeds push through if the membrane is torn or omitted
Quick decision guide by shed type:
| Shed type | Best base option | Why |
|---|---|---|
| Small timber shed (up to 8 × 6 ft) | Gravel + plastic grid | Drainage, low cost, easy DIY |
| Heavy summerhouse or log cabin | Concrete slab or reinforced sub-base | Needs rigid, load-bearing platform |
| Plastic shed | Gravel + plastic interlocking grid | Grid spreads load; gravel drains |
| Medium timber shed on clay soil | Gravel + MOT Type 1 sub-base | Prevents sinking in soft ground |
Choosing the right stone: what works and what to avoid
Stone choice is where most DIY gravel bases go wrong. The wrong material either compacts poorly, migrates freely, or retains too much moisture.
Recommended stone types:
- 20 mm crushed/angular stone — the go-to choice for a shed base on gravel. Angular edges interlock under compaction and resist movement. Ask your supplier for “20 mm crushed aggregate” or “20 mm crusher run topping”.
- MOT Type 1 — a graded crushed limestone or granite sub-base material containing a mix of particle sizes from 40 mm down to fines. It compacts very firmly and is the right choice for a sub-base layer on soft or uneven ground beneath your gravel topping. Available from most UK aggregate suppliers including Poweraggregates.
- Pea shingle / pea gravel — rounded, washed stone in the 6–10 mm range. Drains well and looks tidy, but because it is rounded it does not lock together. Use it only as a decorative topping over a compacted angular sub-base, or in a fully contained frame. On its own as a structural layer, it rolls underfoot and under load.
What to avoid:
- Very fine gravel or sharp sand — compacts into a near-impermeable layer and holds moisture
- Loose washed stone without fines in an uncontained pad — it behaves like ball bearings
- Recycled mixed hardcore with soil or organic material — unpredictable settlement
Angular vs rounded stone: angular crushed stone has fractured faces that grip each other when compacted. Rounded pea shingle has smooth surfaces that slide. For a load-bearing gravel foundation for a shed, angular always wins. You can read more about choosing the right gravel type for different applications on the Poweraggregates site.
| Stone type | Best use | Compaction | Drainage | Notes |
|---|---|---|---|---|
| 20 mm crushed angular | Main gravel layer | Excellent | Excellent | Best all-round choice |
| MOT Type 1 | Sub-base on soft ground | Excellent | Good | Use under angular topping |
| Pea shingle | Decorative topping only | Poor | Excellent | Must be contained |
| Crusher run | Sub-base or base layer | Very good | Moderate | Contains fines; locks well |
What to check before you start: site, permissions and drainage
Site survey checklist:
- Slope: measure the fall across the proposed pad. Up to 50 mm is manageable with careful edging; more than 150 mm needs a stepped or built-up frame.
- Soil firmness: probe the ground as described above. Clay soils are fine if firm; waterlogged clay is not.
- Tree roots: avoid placing a shed within the root zone of large trees. Roots lift and displace any base over time.
- Proximity to drains: check for inspection covers and underground drainage runs before excavating.
- Frost exposure: in exposed northern UK gardens, a deeper sub-base (100 mm MOT Type 1 plus 75 mm gravel) gives more resilience to frost heave.
Permissions: most garden sheds fall within permitted development rights in England and Wales, meaning no planning permission is needed provided the shed is single-storey, under 2.5 m to the eaves, and not forward of the principal elevation. Scotland and Northern Ireland have their own rules. Always check with your local planning authority if you are in a conservation area or if the shed is unusually large.
Pad size: extend the gravel pad at least 150–300 mm beyond the shed footprint on all sides. This improves drainage, makes maintenance easier, and gives you somewhere to stand when opening the shed door without sinking into soft ground.
Delivery access tip: measure your gate width and the turning space for a delivery vehicle before ordering bulk loads. A standard tipper lorry needs roughly 3 m of width and 10 m of turning space. If access is tight, order bagged stone instead.
Pro Tip: Mark out the pad with pegs and string before ordering materials. Photograph the area and note any drainage channels or slopes — it takes ten minutes and saves expensive mistakes.
Tools and materials you’ll need
Materials:
- Weed-suppressing membrane (geotextile, not thin polythene)
- 20 mm crushed angular stone for the main layer
- MOT Type 1 (optional sub-base on soft ground)
- Pressure-treated timber edging (100 × 50 mm or 150 × 50 mm) or plastic restraint boards
- Galvanised timber spikes or steel rebar (600 mm lengths) for anchoring edging
- Plastic interlocking foundation grids (optional, for the shed floor)
- Galvanised screws or coach bolts for timber frame corners
Tools:
- Spade and shovel
- Wheelbarrow
- Garden rake and lute (levelling rake)
- Vibrating plate compactor (hire from a local tool-hire shop — worth every penny)
- Hand tamper (for corners the plate compactor cannot reach)
- Spirit level and a long straight-edge
- String line and pegs
- Tape measure
- Safety gloves, steel-toecap boots and eye protection
Order 5–10% extra gravel to account for compaction and waste. For pads under about 1 tonne, bagged stone is often easier to handle; above that, a bulk tipped load is more economical.
How to calculate how much gravel you need
The formula is straightforward:
Volume (m³) = length (m) × width (m) × depth (m)
Convert your depth from millimetres to metres first: 100 mm = 0.1 m.
Worked example: a 3.0 m × 2.4 m pad at 100 mm depth = 3.0 × 2.4 × 0.1 = 0.72 m³. Add extra for compaction and waste. 0.72 × 1.1 = 0.79 m³ to order.
Gravel weighs roughly 1.5–1.7 tonnes per cubic metre depending on stone type, so 0.79 m³ is approximately 1.2–1.35 tonnes.
Common shed sizes at 100 mm depth:
| Shed size | Pad size (with 200 mm overhang) | Volume (m³) | Approx. tonnes to order |
|---|---|---|---|
| 6 × 4 ft | 2.2 × 1.6 m | 0.35 | 0.55–0.60 |
| 8 × 6 ft | 2.8 × 2.2 m | 0.62 | 0.95–1.05 |
| 10 × 8 ft (3.0 × 2.4 m) | 3.4 × 2.8 m | 0.95 | 1.45–1.60 |
| 12 × 10 ft (3.6 × 3.0 m) | 4.0 × 3.4 m | 1.36 | 2.05–2.30 |
Cost factors to consider:
- Stone type — MOT Type 1 is generally cheaper per tonne than decorative crushed stone
- Delivery distance and access — tight access or long hauls add cost; bagged delivery is more expensive per tonne but avoids access problems
- Compaction hire — a half-day plate compactor hire typically costs £40–£70 in the UK
- Seasonal pricing — aggregate prices can rise slightly in spring when demand peaks; ordering in late winter often saves money
- Waste allowance — always add that 5–10% buffer
Step-by-step: laying a gravel shed base
The correct sequence is: excavate, compact subsoil, install edging, lay membrane, add sub-base if needed, lay and compact gravel in lifts, check level, then install floor system and place shed. Skipping any step, particularly the edging and the layer-by-layer compaction, is what causes most failures.
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Mark out and excavate. Set out the pad with string lines. Dig out turf and topsoil to firm subsoil — typically 150–200 mm for a light shed, 200–250 mm if you are adding a MOT Type 1 sub-base. Remove all organic material.
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Compact the subsoil. Run the plate compactor over the exposed subsoil before adding any stone. This firms the base and reveals any soft spots you need to address.
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Install the perimeter edging. Fix pressure-treated timber boards (100 × 50 mm minimum) around the pad perimeter, driving galvanised steel spikes or 600 mm rebar through pre-drilled holes into the ground every 600–900 mm. Plasticine House’s gravel shed foundation guide recommends anchoring timbers at corners and mid-spans to resist outward pressure as the gravel compacts. Alternatively, use proprietary plastic restraint boards.
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Lay the weed membrane. Cut geotextile membrane to overlap the edging by 50–100 mm on all sides. Overlap joins by at least 300 mm. This is not optional — without it, weeds push through within a season.
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Add MOT Type 1 sub-base (if needed). On soft or clay ground, spread 50–75 mm of MOT Type 1 and compact it thoroughly before adding the gravel layer. This is your hardcore base for shed stability on difficult ground.
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Lay and compact the gravel in lifts. Spread the first a recommended depth between 7 and 10 cm lift of 20 mm crushed stone, rake level, then compact with the plate compactor. Compact in overlapping passes. Lightly dampen very dry stone before compacting — it helps the fines bind. If your total gravel depth exceeds 100 mm, add a second lift and compact again rather than filling the full depth at once.
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Check level across diagonals. Place a long straight-edge and spirit level across the pad in both directions and on the diagonals. Rake and recompact any high or low spots. A tolerance of ±10 mm across the pad is acceptable for most sheds.
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Install floor system and place shed. Lay plastic interlocking grids or timber bearers on the compacted surface, then position the shed. Secure the shed to the base with ground anchors or frame brackets — essential in exposed UK gardens.
Pro Tip: Hire a plate compactor even for small pads. Hand-tamping alone leaves the base under-compacted, which leads to settlement within the first winter. A half-day hire is one of the best investments in the whole project.
How to pair a gravel base with common shed floor systems
The gravel pad is the foundation; what you put on top of it determines how well the shed floor performs over time.
Plastic interlocking foundation grids sit directly on compacted gravel and spread the shed’s weight across the full pad area. They keep the shed floor lifted clear of the stone surface, improving ventilation and reducing moisture contact with timber. This pairing works particularly well on moisture-prone or clay sites. Plastic grids do not absorb water, so they will not rot, and they are straightforward to level by adjusting the gravel beneath individual sections.
Timber bearers on skids are the traditional approach for wooden sheds. Pressure-treated 100 × 75 mm or 150 × 75 mm bearers sit directly on the compacted gravel, running perpendicular to the shed floor joists. The gravel provides drainage beneath the bearers, which is the critical detail — a bearer sitting in standing water rots in a few years regardless of treatment. Check and re-level bearers every two to three years.
Concrete pads or paving slabs can be used in combination with a gravel surround, but if you are going to the trouble of laying concrete, a full slab is usually more practical than a hybrid. Paving slabs for a shed base work well for smaller structures where you want a firm, flat surface without mixing concrete — lay them on a compacted sand and MOT Type 1 bed rather than directly on loose gravel.
Avoidances:
- Do not place a heavy log cabin directly on uncontained gravel without bearers or grids — point loads from the corner posts will sink into the stone
- Avoid untreated timber bearers on any gravel base; moisture wicking from the stone will accelerate decay
- Do not skip the membrane under grids — weeds push up between the grid cells and are difficult to remove once established
For more on pairing base types with different shed constructions, the steel-framed shed guide on the Poweraggregates site covers alternative floor system options.
Maintenance, likely problems and how to fix them
A gravel shed base needs roughly one hour of attention per year to stay in good condition.
Annual maintenance checklist:
- Re-top with fresh 20 mm stone where the surface has compacted down or migrated
- Re-level the pad after heavy rain or a hard winter — check with a spirit level
- Inspect the weed membrane for tears and patch with overlapping geotextile
- Pull or spray any weeds that have pushed through
- Check edging boards or restraints for movement and re-drive any loose spikes
- Inspect shed anchors and tighten or replace as needed
Common problems and fixes:
Settlement or tilting: usually caused by under-compaction or soft spots in the subsoil. Lift the shed temporarily, excavate the low area, add MOT Type 1, recompact and re-top with gravel.
Surface water pooling: check that the pad slopes very slightly (5–10 mm across the width) away from the shed. If the surrounding ground has risen or the pad has sunk, re-grade the gravel and check that the perimeter edging is not trapping water.
Gravel migration: stone escaping beyond the edging means the perimeter has failed. Extend or replace the edging boards, drive new anchoring spikes, and rake escaped stone back in.
Persistent weeds: a torn or absent membrane is the cause. Lift the gravel in the affected area, replace the membrane, and re-lay the stone. Spot-treating with a path weedkiller buys time but does not fix the root cause.
Pro Tip: The best months to build or repair a gravel base in the UK are April through September. Avoid laying in frozen ground or during prolonged wet spells — waterlogged soil will not compact properly and you will be re-doing the work within months. If you must work in autumn, cover the excavated area overnight with a tarpaulin to keep it dry.
For more on managing backyard drainage around garden structures, the Modern Yardz drainage guide covers complementary techniques.
Supplier-backed tips from Poweraggregates: what to ask and watch for
Ordering the wrong stone or the wrong quantity is the most common and most avoidable mistake. These are the questions worth asking any aggregate supplier before you place an order.
Questions to ask your supplier:
- What is the stone grading? (Ask for the particle size range in millimetres, not just the nominal size)
- Is the stone washed or unwashed? Washed stone is cleaner but has fewer fines; unwashed crushed stone compacts better for a structural base
- What is the typical moisture content at delivery? Very wet stone is heavier and harder to compact
- What is the delivery load size and offloading method? A grab lorry can place stone precisely; a tipper will dump it at the nearest accessible point
- Can you supply bagged stone for tight-access gardens?
How to spot the right stone on delivery:
- Angular crushed stone has sharp, fractured edges and a dusty surface from the fines — that is correct
- Rounded pea shingle looks smooth and clean — fine as a topping, not as a structural layer
- If the stone looks muddy or contains visible soil, reject it; organic contamination causes settlement
Containment and compaction from Poweraggregates’ experience:
The single most common failure on a DIY gravel base is skipping the perimeter frame. Clean angular stone without a rigid edge will spread outward under the shed’s weight and foot traffic, losing level within one or two winters. A pressure-treated timber frame costs very little relative to the whole project and is the difference between a base that lasts a decade and one that needs rebuilding in three years.
Pro Tip: If your garden access is narrow, ask Poweraggregates about bagged decorative stone options. Bags can be carried through a standard gate and emptied precisely where needed, avoiding the need for a large delivery vehicle entirely.
The mistake almost every DIYer makes
The gravel base is one of those jobs where the preparation is the job. Most people spend their energy on the shed itself and treat the base as an afterthought. The result is a frame with no edging, stone that has spread to the borders by the second winter, and a shed that rocks on a tilted pad.
The fix is not complicated. A pressure-treated timber frame, driven into the ground with galvanised spikes, costs under £30 in materials for a standard 8 × 6 ft pad. It takes an afternoon. Without it, you are relying on friction alone to hold the stone in place, and friction loses every time against two years of British weather and the weight of a loaded shed.
The second mistake is skipping the plate compactor. Hand-tamping feels adequate on the day, but it leaves the lower layers loose. The first hard frost or heavy rain finds those voids and the base drops unevenly. Hire the compactor. It is not optional.
If you are unsure about stone type, depth, or quantities for your specific site, contact Poweraggregates directly. The team has handled everything from small domestic pads to large commercial groundworks and can advise on the right product and quantity for your project.
Ready to order your materials? Poweraggregates has everything you need
Skip the guesswork on materials. Poweraggregates supplies 20 mm crushed angular stone, MOT Type 1 sub-base aggregate, pea shingle, and weed-suppressing membrane, all available in bulk or bagged quantities with delivery across the UK and Ireland.
Calculate your pad volume first (length × width × depth, then add 10%), then decide whether bulk or bagged delivery suits your access. For most standard shed pads up to about 10 × 8 ft, one to two bulk bags covers the gravel layer comfortably. Tight access? Bagged stone goes through any standard garden gate.
Browse the full range of aggregates and decorative stone on the Poweraggregates site, or head straight to the shop to order bagged products. For sub-base materials including MOT Type 1, the building products page lists available grades and pack sizes. The team is available by phone or email to confirm specifications and delivery options before you order.
Sources
- Your step-by-step guide to a gravel shed base | Summerhouse24
- Can you put a shed on gravel? | Buy Sheds Direct
- How to build a gravel shed foundation essential guide – Plasticine House
FAQ
Is gravel a good base for a shed?
Yes, for most small and medium garden sheds a gravel base drains well, costs less than concrete, and is straightforward to build yourself. It performs best with angular 20 mm crushed stone, a compacted depth between 7 and 10 cm for small to medium sheds (more for larger or heavier structures), and a rigid perimeter to prevent the stone from migrating.
What is the cheapest way to base a shed?
A compacted gravel pad is generally the cheapest practical shed base option. You need gravel, a weed membrane, and pressure-treated timber edging, plus a hired plate compactor for half a day. A concrete slab costs more in materials and typically requires more labour or a professional pour.
How thick should a gravel base be for a shed?
A compacted depth between 7 and 10 cm of angular stone is the standard recommendation for small to medium sheds. For larger or heavier structures, a deeper gravel layer or additional MOT Type 1 sub-base may be required. On soft or clay ground, add a 50–75 mm layer of MOT Type 1 beneath the gravel for extra stability, bringing the total excavation depth to around 150 mm.
How much gravel do I need for a 10 × 12 shed base?
A 10 × 12 ft shed (approximately 3.0 × 3.6 m) with a 200 mm overhang gives a pad of roughly 3.4 × 4.0 m. At 100 mm depth, that is 1.36 m³. Add 10% for compaction and waste, and you need approximately 1.5 m³, or around 2.05–2.30 tonnes of 20 mm crushed stone.