Last Modified: April 5, 2024

How to Lay Slate Chippings

the Complete Step-By-Step, DIY Guide

Close up of grey slate rock

By Ben Parrot - Landscape Gardener & Amateur Geologist

Overview

Welcome to our DIY guide on how to lay slate chippings. Renovating your garden is easier than you might think with slate chippings. These versatile decorative aggregates offer numerous benefits, both aesthetic and practical, coming in a range of eye-catching colours and laying slate chippings is very DIY-friendly. This makes them a great material for decorating, from highlighting garden ornaments through to embellishing slate water features. They can be laid in six straightforward steps:

  1. 1
    Choose: The ideal colour and size for your project.
  2. 2
    Calculate: Measure up and use our online calculator to estimate your required materials.
  3. 3
    Prepare: Get the area ready for area digging.
  4. 4
    Excavation: Dig out the base of the space.
  5. 5
    Membrane: Laying a permeable weed membrane.
  6. 6
    Finish: How to put slate chippings down and rake them level.

But how do you choose the right slate chipping for your landscaping project while ensuring they’re correctly installed? In this comprehensive DIY, 'how-to' guide, we walk you through the whole process, step-by-step to help you achieve a visually appealing result that will last. From how to select and prepare your area, this guide provides the best way to lay slate chippings so that it will keep your slate neatly contained and looking great for the long-run.

Note: If you are laying a slate path or driveway, the methodology differs slightly. We have step-by-step guides about both topics in our articles: how to lay a gravel path and installing a gravel driveway.

Finally, be sure to take advantage of our new 'Pebble Picker' utility, accessible from the sidebar or menu. This resource simplifies the process of selecting and perusing different decorative aggregates according to colour and type.

Blue slate garden. Jpg

Step 1 - Choosing the Right Slate Chippings

When it comes to selecting the best decorative gravel for your garden slate chippings project, there are some vital factors to consider before you install slate chippings. Firstly, the ideal size is usually determined by the intended application. Aside from that, there is the all important desired slate chipping colour, which we will begin from.

The Colourful Shades of Slate

As a decorative aggregate, slate is of the fine grained type. Slate comes available in an array of different shapes and stunning colours, with the most popular being:

  • Blue slate chippings
  • Grey slate chippings
  • Plum slate chippings
Green plum and blue slate colours

Size Matters

The size of slate chippings can range from very small, right up to the largest slate stones, known as paddlestones. The optimal size of slate chippings depends on your specific project requirements, with smaller stones better for flatter results and larger for greater coverage.

Slate Mini Mulch for Flat Pack Paths

The shape of your decorative aggregates is important. When you lay gravel for pathways and desire a smooth finish, 2-10mm slate mini mulch or 20mm slate chippings are best because they pack down the flattest. Awkwardly shaped stones won't pack as flat, resulting in a less level surface.

Use 20mm Slate Chippings or Larger for Driveways

Thus, we don't recommend every size of slate chippings for driveways, due to the smaller chippings tendency to crumble under the tyre treads of heavier traffic, even although the driveway remains stable. In particular, mini mulch is not suitable for driveways due to their size and can end up lodged in tyre treads.

However, where the potential of some minor deterioration to the slate chippings aesthetic is not of concern, 20mm to 40mm slate chippings would be the best choice if you're looking for a visually striking alternative to traditional block paving using paving slabs.

Mini mulch to boulders sizes

Ground Cover and Borders - Go Large!

On the other hand, if you’re looking to create ground cover or surround a pond, 40mm slate chippings can be a great option, as a larger size can give greater coverage while adding a great texture.

Step 2 - Calculate Your Material Requirements

Measuring a garden for a gravel path

Taking Measurements

Before you begin your slate chippings project, measure the length and width of the area, in meters. If the area isn't a perfect square or rectangle, divide it into smaller, measurable sections. Don't forget to include any curves or irregular shapes in your measurements. Multiply the length and width to calculate the area in square meters. This is crucial as slate chippings are generally sold by volume, which is based on the area and depth of coverage.

You will also require landscape fabric pins or staples and weed membrane. If you are making a path, you should also add the materials required for a sub-base.

What Depth Should Chippings be Laid?

If you're wondering, "How deep should you lay slate chippings?", the answer depends on the type of feature you are building.

  • For most garden projects, it's recommended to lay mini mulch and 20mm slate chippings to a depth of around 4-5cm (1-2").
  • If you're using 40mm slate chippings, they should ideally be laid to a depth of 5-6cm (2-3").
  • As for 50-150mm slate paddlestones, these should be laid slightly deeper, around 6-10cm (3-4"). Despite their larger size, they will settle nicely. However, due to their size, they are not recommended for creating paths and driveways.

*For pathways, a minimum of 6-8cm is the recommended depth for your slate chippings.

Garden with grey chipped slate

Use an Online Calculator

To help to eliminate guesswork and make your garden slate chippings project easier and more efficient, consider using our online gravel calculator. All you need to do is input the dimensions of your space and the calculator will automatically compute the volume of slate chippings you'll require, and then convert into multiples of bulk bag sizes for convenience and pricing.

Step 3 - Marking Out the Area

Marking out the area for a gravel border. Jpg

Proper ground preparation may be done prior to taking delivery of your feature stones, but it isn't advisable to begin too far in advance of taking delivery, as many issues could hinder your projects progress, such as erosion from heavy rains.

It's best to begin by marking out the area where the slate chippings will be laid using a garden hose, string and/or wooden marking sticks. From there it is advisable to take a moment to assess your design before proceeding to the next step.

Step 4 - Do You Dig It? Yes!

4.1 - For Ground Cover & Borders

If you're planning to use slate chippings in a feature that won't involve foot traffic, using a shovel, you'll need to excavate the area to a depth of approx:

  • 4-5cm (1-2") for mini mulch or 20mm diameter chippings
  • 5-6cm (2-3") for 40mm slate chippings
  • 10-12cm (4-5") for larger paddlestones

If you aren't building a pedestrian area, you may now move on to step 5, laying a membrane.

Gardening tools in a wheelbarrow

4.2 - Slate Paths & Areas of Traffic

When it comes to using slate for pathways, it's best to dig down at least 10cm deep. This depth allows room for a layer of crushed stone, or MOT type 1 sub-base, to be used as a sub-base beneath the slate. This is vital to the stability and strength of your walkway or drive.

4.3 - Creating a Stable Sub-base

A firm sub-base is essential for a durable slate pathway. Distribute your crushed rock or hardcore uniformly to a depth of roughly 20% higher than the intended 'compacted depth'. Therefore, add at least 7cm for compacting to a 5cm depth after compression, in soils that drain well. Add more for poorly drained soils. Use a hand tamper and sledge hammer or a plate compactor on the surface until you establish a firm, even surface. Ensure that each segment is level, either with a laser level or a builder's spirit level.

Mot type 1 sub base for chippings driveway

Step 5 - Weed Membrane

As a slate chippings cover for exposed soil, weed membranes work by being put under slate chippings to help inhibit weeds, aid in drainage and ensure stability. Many people often ask, "Will plants grow through slate chippings?"

Plants can grow through slate chippings depending on the plant type, depth and size of chippings, presence of a weed barrier, and accumulated organic matter. However, thicker chippings and regular maintenance can reduce this likelihood. Examples include bamboo and Japanese knot weed.

When selecting a weed membrane, avoid using black plastic or bin liners, as these materials are not suitable. Instead, opt for a permeable, heavy duty membrane, or a geo-textile landscaping fabric, which will allow water to drain while effectively blocking weeds from emerging.

Here’s how to properly install a weed-resistant membrane:

  1. 1
    Lay the sheet over the designated area, making sure the membrane conforms to the shape of the dug-out space.
  2. 2
    If there are any gaps, simply overlap off-cuts of the membrane at a minimum of 15-30cm to cover them.
  3. 3
    Secure the membrane in place by knocking landscape fabric pins or staples in around the border.

Now that your ground is prepared, it’s time to lay your slate chippings.

Laying down landscaping fabric for weed protection

Step 6 - Spreading Your Chippings

Well done, you're almost finished. Now that your foundation is down and borders are set, it's time to lay the slate chippings. Utilizing a wheelbarrow or large buckets, transfer the stones into piles, distributing them around the area to reduce the amount of raking needed for the initial layer. Lastly, spread them uniformly, aiming for a depth of 3-5cm (1-2 inches), using a metal garden rake to create a level and smooth surface. Congratulations, you've completed it!

Laying plum chippings on to weed fabric. Jpg

Maintenance

Occasional maintenance of your slate chipping feature is crucial for maintaining the visual appeal and functionality. This includes removing leaves and other debris, as well as checking for weed germination. To remove debris from your slate chippings, use a leaf blower or broom to gently sweep the surface.

Alternatively, a pressure washer can also be used to clean slate chippings. Adjust the pressure washer to a low setting, then use it to spray the slate chippings and eliminate any dirt and grime. In addition to removing debris from planting areas, regularly inspect your slate chippings for weed growth and promptly eliminate any that are present.

Occasional Replenishment

If you notice the top laid beneath slate chippings becoming thin or patchy over time, add additional chippings to the area to replenish them.

1raking leaves off a slate driveway. Jpg

Summary

In conclusion, slate chippings are an economical and versatile option for garden landscaping, offering numerous benefits such as low maintenance, weed prevention and natural beauty. By following this guide on how to lay slate chippings you’ll be ready to make a stunning and functional  feature for your outdoor space. Remember that the key to laying slate chippings successfully is in proper preparation, attention to detail and occasional maintenance.

1black slate chips front garden. Jpg

FAQs

Will plants grow through slate chippings?

Plants can grow through slate chippings, but their ability to do so depends on factors like the depth and size of the chippings, whether there is a weed membrane laid, the type of plant and how much organic matter has been allowed to accumulate. Weeds will generally struggle without significant decomposed leaf and debris build up, if a membrane is in place.

However, while some hardy plants with robust roots, such as bamboo, can push through most barriers, especially if thinly layered, a combination of thicker chippings, a weed barrier, and regular maintenance can significantly reduce the occurrence of all but the hardiest plants.

Why are my slate chippings turning white?

Moisture is drawn to the surface, causing salts in the soil, water, sand, gravel and cement to be dissolved, retaining moisture. As this moisture evaporates, the salts are left behind and the slate develops a white haze, giving the stones an unattractive appearance. This process is natural and does not cause any damage.

Do you have to wash slate before laying?

Washing slate chippings before laying them is advisable to remove dust, dirt, and debris, revealing their true colours and preventing potential weed growth. This process also enhances stability by settling the chippings and ensures a clean and visually appealing appearance for your garden or landscaping project.

How much does a bulk bag of slate chippings cover?

A bulk bag of slate chippings, when spread at a depth of 5cm, typically covers an area of approximately 20 square meters. It's important to note that the coverage may vary slightly depending on factors like the size and shape of the chippings and the evenness of the surface, so it's advisable to measure the actual area you plan to cover and use an online gravel calculator to get an accurate estimate.

How deep should slate chippings be?

While it will vary depending on the specifics of each project, here are some recommended depths for slate chippings:

  • Landscaping and decorative use: 5 - 10cm.
  • Garden paths should be a minimum of 5 - 7.5cm.
  • Driveways should be a minimum of 10 - 15cm.

There are many colours of slate chippings available for your project. Check out them out!

About the author 

Ben Parrot is a landscape gardener and amateur geologist. He is the founder of Outdoor Aggregates, with the mission to create the first encyclopaedia for decorative aggregates. From natural stone through to decorative bark, these aggregates are critical to garden and landscape design, universally.

The problem: There isn't any place where all the different types of decorative landscaping materials and construction aggregates can be found, nor are the specifications of each type readily available. So, enriched by his extensive experience, and inspired by the timeless elegance and raw beauty of stone and rock, etched by nature's artistry over millennia, Outdoor Aggregates was born.