If you are filling a raised bed, it’s easy to work out the depth of soil you’ll need. Simply measure from the bottom of planter to about 5cm below the top. This will allow you plenty of room to add plants.
Experts state that the recommended depth of topsoil for creating lawns from turf or seed is 10 to 15cm. This allows the roots of a newly laid lawn to establish themselves.
Lawns generally have a large surface area and purchasing topsoil without prior calculation can have two outcomes both of which are not favourable for different reasons.
If you are going to have a tree or two in your lawn, then bear in mind you will have to adjust the soil composition accordingly. Grass and trees will need different volumes of topsoil and compost.
Since tree roots are ingrained deeply in the soil you will need to have a greater depth of topsoil around the trees. A standardized depth of soil recommended for tree cultivation is around 3 feet comprising of subsoil and topsoil. In this mix of soil, topsoil should be around 30cm.
For most planting projects such as for a herbaceous border, you will need around 15 to 20cm of topsoil.
Firstly, you need to think about what veggies you plan to grow as the depth of topsoil will vary. For example, “salad” vegetables and surface crops like tomatoes, beans or courgettes will be perfectly happy with a depth of 15 – 20cm whereas root vegetables such as carrots, potatoes and parsnips will need approximately 30 – 40cm to do well.