Drainage Gravel 20mm

20mm Drainage Gravel is a popular choice for residential and commercial projects and is commonly used for:

• French drains
• Retaining wall drainage
• Trench drainage
• Backfilling around agricultural (AG) pipe
• Soakwells and drainage pits
• Stormwater drainage systems
• General landscaping drainage

20mm Drainage Gravel is one of our most popular gravel sizes and provides excellent drainage while minimising soil and debris movement. It is an excellent choice for backfilling behind retaining walls, using in French drain systems, and surrounding larger drainage pipes and pits.

To calculate how much 20mm Drainage Gravel you need for your project, measure the length and width of the area where the gravel will be placed.

Next, determine the desired depth of the gravel. The required depth will vary depending on your project and the area you need to fill.

Once you have your length, width, and depth measurements, you can use our cubic metre calculator above or calculate the volume manually using the following formula:

Volume = Length × Width × Height

Note: We recommend adding at least 10% extra to your total calculated volume to allow for settling and levelling.

We recommend using Bidum filter cloth (geofabric) and AG pipe to improve water flow and reduce blockages caused by soil and sediment. For relatively little extra cost and effort, adding these two products can significantly improve the performance of your drainage system and help future-proof your hard work for years to come.