As an approximate guide, one bulk bag will cover:

• 10–12m² at a depth of 50mm

• 6.5–7.5m² at a depth of 75mm

• 5–6m² at a depth of 100mm

Garden borders, rockeries, and flower beds commonly require around 50mm to 75mm of decorative slate, while driveways and heavy foot-traffic pathways may require 75mm to 100mm depending on the sub-base and expected usage.

These figures are estimates only. Actual coverage will vary according to the bag weight, ground conditions, compaction and the accuracy of the excavation.

Not sure how many bags you require? Call our Rugby team on 01788 866945 with the length, width and required depth.

40mm blue slate decorative chippings are intended as a decorative surface, border, or rockery feature. Colour, natural shade variations when wet or dry, and flat angular shape can vary according to the source of the slate.

You can use our online calculator at https://www.melbros.com/calculator

Excavate the area to the required depth and prepare the ground appropriately. A suitable geotextile membrane may be required to prevent weed growth and stop the subgrade from mixing.

Spread evenly over the prepared sub-base to the recommended depth. Rake or lay by hand to ensure an even, flat distribution across the entire area.

Check the finished surface level and slope to ensure proper drainage away from surrounding structures. Ensure the depth is consistent to prevent exposed patches or uneven surface layers.

Requirements vary according to ground conditions, loading, and the intended use of the surface. Follow the project specification or seek professional advice where appropriate.

Available for collection from our Rugby branch or local delivery using our own fleet.

Bulk bags will normally be delivered by a crane-equipped lorry. Delivery is kerbside and the final offloading position is always subject to safe access and the driver’s discretion.

Please tell us before delivery about:

• Narrow roads or restricted entrances
• Parked vehicles or limited turning space
• Overhead cables, trees or other obstructions
• Soft, sloping or unsuitable ground
• Any other access concerns

Enter your postcode on the product page to check your delivery area. We’ll confirm the delivery date after your order is placed.

What is 40mm blue slate?

40mm blue slate is a decorative, natural aggregate made from crushed slate rock. It features large, flat, angular pieces with striking deep blue, grey, and subtle purple tones that intensify when wet.

What is 40mm blue slate used for?

40mm blue slate is commonly used as a decorative ground cover for garden borders, flower beds, rockeries, footpaths, and around ponds. Its flat shape also helps suppress weeds and retain soil moisture.

What is the difference between 40mm slate and 20mm slate?

40mm slate consists of larger, flatter pieces that stay in place better and provide a bold, textured look for large borders or ground cover. 20mm slate consists of smaller, flatter pieces that pack down tighter, making it easier to walk on for footpaths.

Is 40mm blue slate fish-friendly?

Yes. Slate is an inert, natural rock that will not alter the pH level or chemical balance of water, making it completely safe for use in fish ponds, water features, and aquatic environments (though washing it beforehand is recommended to remove dust).

Does 40mm blue slate fade in sunlight?

No. Natural slate is highly durable, weather-resistant, and UV-stable, meaning its natural blue-grey colour will not fade, wash out, or bleach over time in direct sunlight.

Why does the colour of blue slate change?

Being a natural stone, blue slate appears as a soft, matte greyish-blue when dry, but turns into a vibrant, deep midnight blue with metallic tones when wet or raining.