For a lasting finish, build a compacted sub-base, add weed membrane, then spread 30–50 mm of slate chippings and rake level with firm edging.
Slate chippings give paths, borders, and seating areas tidy lines with low upkeep. This guide shows the full method from ground prep to the final rake, with clear depths, edging choices, drainage tips, and a simple cost planner. You’ll see what to buy, how much to order, and the exact steps to get a neat, stable surface that holds up in rain and foot traffic.
Putting Slate Down In A Garden: Depths, Base, Tools
Good results start with a stable base and the right depth of stone. A weed-suppressing fabric stops stones from sinking and keeps maintenance low. Depth varies by chip size and footfall, while edging keeps the finish crisp. Below is a compact reference you can use while ordering materials.
Depths And Coverage Guide
| Chip Size | Typical Depth | Coverage Per Tonne* |
|---|---|---|
| 20 mm slate | 30–40 mm | 14–18 m² at 30–40 mm |
| 40 mm slate | 40–50 mm | 12–15 m² at 40–50 mm |
| Decorative gravel (10–20 mm) | 30–50 mm | 12–18 m² at 30–50 mm |
*Coverage varies with chip shape, moisture, and supplier bag weight. Use a small buffer when ordering to stay on track.
Plan The Area And Mark Levels
Walk the route where the slate will go. Check for low spots after rain, any drain covers, and tree roots. Decide the finished height so doors clear, edges align with lawn, and water runs away from buildings. Peg out the edges with string and mark a gentle fall of about 1:60 to 1:80 where water needs to move off the surface.
Measure For Quantities
Measure length and width to get area. Multiply by stone depth (in meters) to get volume. Add 5–10% for shaping and top-ups. For paths, treat curves as rectangles; the extra covers trims and feathered edges.
Gather The Right Tools And Materials
Tools
- Spade, digging fork, and a solid rake
- Hand tamper or plate compactor (wacker)
- Builders line, pegs, tape measure, and spirit level
- Stanley knife and scissors for the fabric
- Wheelbarrow and a stiff brush
- Gloves, dust mask, and eye protection
Materials
- MOT Type 1 or crushed stone for the sub-base
- Geotextile weed membrane (puncture-resistant, permeable)
- Slate chippings (20 mm for paths; 40 mm for deeper cover or softer look)
- Edge restraints: steel, aluminum, timber, or setts
- Sharp sand (thin blinding layer if needed over sub-base)
Excavate And Prepare Ground
Strip turf and soft topsoil to reach firm ground. For garden foot traffic, aim for a total dig of about 120–150 mm, which allows room for sub-base and stone. Widen the dig past the finished line by the same depth as your sub-base; this supports the edges and stops slump.
Rake the base level. Remove roots and rubble. If you’re on heavy clay, check that water has a path to soakaway or a lower bed. Low spots can be filled with sub-base during the next step.
Lay And Compact The Sub-Base
Tip in MOT Type 1 in 50 mm layers. Lightly damp each layer, then compact with a plate compactor. Two passes lengthways and crossways give a tight bind. Target depth is 80–100 mm for walkways and seating zones, more if a bin store or heavy pots will sit on top.
Run a straightedge over the surface and check falls. Add a thin 10–15 mm blinding of sharp sand only if the sub-base texture needs smoothing before fabric goes down. Keep levels true; humps telegraph through to the slate.
Fit The Weed Membrane
Roll out geotextile fabric over the compacted base. Overlap joints by 100–150 mm and pin with U-pegs or offcuts. Cut neat X-shapes around plants and posts. The fabric lets water through, blocks light to weeds, and stops chips from working into the base over time.
Install Solid Edging
Edging locks the stone in and gives a tidy line. Push metal or plastic lawn edging into the firm sub-base and fix to the height you set earlier, or bed stone setts on a narrow strip of mortar along the margin. Straight runs look best with steel or aluminum; curves are easier with flexible plastic systems. Check the top sits slightly proud of the final slate level to catch strays when you rake.
Spread Slate And Rake To Finish
Barrow slate onto the membrane and spread with a garden rake. Start with a loose layer, then top up to the target depth from the table. Pull stones away from plant stems by a hand’s width to allow air flow. For paths, aim for an even 30–40 mm with 20 mm chips. For bigger chips, 40–50 mm gives stable coverage without eating budget.
Walk the area and listen. A crunch underfoot is normal; a hollow sound signals thin coverage. Add a final skim where needed and brush stray chips off paving and thresholds.
Drainage, Planting, And Soil Health
Stone mulches limit evaporation and keep soil cooler in hot spells. Around perennials and shrubs, pull chips back each spring and add organic matter beneath the fabric cut-outs if growth is slow. In wet zones or on clay, shape shallow swales or direct run-off to a soakaway so water doesn’t sit on paths. Keep the finished surface below damp-proof course by at least 150 mm near walls.
Edging Choices: Pros And Trade-offs
Steel Or Aluminum
Clean lines and thin profiles. Fast to fix on straight runs. Little visual bulk. Can sit almost flush with lawns for easy mowing.
Timber
Warm look and easy DIY cutting. Needs ground contact-rated boards and solid spikes. Expect periodic checks and the odd swap after several seasons.
Stone Setts Or Bricks
Premium finish and weighty restraint. Set on a tight mortar bed with joints pointed. Best where a path meets a patio or steps.
Common Mistakes And Simple Fixes
- Skipping the sub-base: Leads to dips and wavy paths. Add 80–100 mm of MOT Type 1 on the next refresh and compact well.
- Thin coverage: Anything under 30 mm on 20 mm chips shows fabric and scuffs fast. Top up to depth and rake flat.
- No edging: Chips spread into lawns and beds. Install a discreet restraint and reset the margin.
- Poor drainage: Flat surfaces hold water. Regrade sub-base for a gentle fall or add a soakaway off to the side.
- Fabric above the surface: Trim clean and tuck under chips to prevent UV damage and trip points.
Care And Seasonal Upkeep
Slate needs light attention through the year. Hand-pull odd weeds that root in wind-blown silt. Top up thin patches every year or two, especially on narrow desire lines. After storms, brush chips back from thresholds and gulley tops. Where leaves collect, lift with a plastic leaf rake or a blower set low to avoid moving stones.
Safety And Handling
Wear gloves and eye protection when cutting fabric and moving stone. Dampen chips during dry spells to keep dust down. Use a dust mask when pouring from bags. Keep barrow loads moderate on slopes and take small steps while tipping to stay balanced.
When A Heavier Build Helps
For bin stores, barbecues, or spots that take frequent trolleys, deepen the sub-base to 100–150 mm and compact in stages. Where roots push from below, use a thicker sub-base and a stiffer edging so the surface holds shape longer.
Stone mulches can suppress weeds and reduce watering on beds and borders. See the RHS guidance on mulching for wider planting benefits and soil tips. For base build questions and when to include a sub-base under different surface types, the trade notes in Pavingexpert’s sub-base FAQ give clear context on depth and compaction.
Step-By-Step Recap You Can Follow
- Mark out and set falls. Peg lines and set a gentle fall away from buildings.
- Excavate. Remove turf and soft soil to reach firm ground, widening the dig by the base depth.
- Lay sub-base. Add MOT Type 1 in 50 mm layers, damp, and compact each pass. Target 80–100 mm.
- Smooth as needed. Add a thin blinding of sharp sand only where required to remove high spots.
- Fit membrane. Roll, overlap, pin, and trim clean around posts and plants.
- Install edging. Fix steel, aluminum, timber, or setts to the final height line.
- Spread slate. Barrow and rake to 30–50 mm depth per chip size.
- Final checks. Walk the area, top up hollows, brush up the margins, and tidy transitions.
Choosing Between 20 Mm And 40 Mm Chips
For paths, 20 mm gives a firm feel underfoot and sits snug with less rolling. Around shrubs and in wide beds where traffic is light, 40 mm gives a bold look and hides fabric with fewer fines. Match the depth from the table and keep the finish consistent across each zone so repairs blend in later.
Quick Cost And Quantity Planner
Use these ready sums to order with confidence. Figures assume 40 mm depth for beds and 35–40 mm for paths, density near 1.6 t/m³, and a small buffer for odd corners.
| Project Area | Volume At 40 Mm | Slate Needed |
|---|---|---|
| 5 m² | 0.20 m³ | ≈ 320 kg |
| 10 m² | 0.40 m³ | ≈ 640 kg |
| 15 m² | 0.60 m³ | ≈ 960 kg |
| 20 m² | 0.80 m³ | ≈ 1,280 kg |
Design Tips That Save Time Later
- Break long runs: Add stepping stones through deep beds so feet don’t push chips aside.
- Blend batches: Open two bags at once and mix as you go for a uniform shade.
- Mind leaf drop: Near deciduous trees, choose 20 mm chips for easier raking.
- Use weed rings: Around shrubs, cut firm circles from spare fabric and top with a neat collar of slate.
- Protect edges: Where paths meet lawns, add a hidden steel strip to reduce mower scuff.
Troubleshooting After Heavy Rain
If fines puddle on the surface, brush lightly once dry and check falls. Where water sits, peel back a section, lower the sub-base slightly toward a soakaway or channel, and relay. If chips migrate onto paving, lift the edge height by several millimeters so the margin catches loose pieces.
How To Refresh An Old Slate Area
- Scrape off leaf litter and silt with a flat shovel and brush clean.
- Top up thin zones to the original depth and mix with the old layer to blend shade.
- If weeds have rooted through, lift a strip, repair the fabric overlap, and relay.
- Reset edging that has drifted using fresh fixings or a deeper spike.
Checklist Before You Order
- Area measured and finish level set clear of thresholds and damp-proof courses
- Plan for a fall where run-off needs to move
- Sub-base depth chosen for traffic type
- Membrane, pins, and edging all sized for the footprint
- Chip size matched to use (20 mm for paths; 40 mm for wide beds)
- Extra 5–10% added for curves and top-ups
Why This Build Lasts
The layered approach—firm sub-base, breathable fabric, locked edges, and the right stone depth—stops ruts, keeps weeds low, and sheds water cleanly. With this setup, yearly upkeep comes down to a brush, a quick top-up in high-traffic lines, and small trims around stems. The finish looks sharp on day one and stays tidy through the seasons.