When laying a lawn, the height and amount of topsoil is important. It serves as the basis for classic lawn or sod. For this reason, do not use too little. Read here how much topsoil should be used under lawn.
- topsoil layer for lawn should be 15-20 cm thick
- for sod about 2 cm less
- compaction, however, reduces total height
- therefore calculate with more material (approx. 2 to 5 percent surcharge)
Topsoil: How high?
How high must be the layer of topsoil for the lawn, concerns many gardeners. Whether it is a seed or rolled lawn, the layer of topsoil must always be high enough. Only this will provide the grasses with sufficient root support and an easily accessible nutrient base. According to experience, a height of 15 to 20 centimeters has been established for the topsoil layer. The pit for the lawn is dug to the appropriate depth.
Note: Additional sand must be worked into many topsoils to improve the structure. However, this does not affect the overall height of the layer.
Topsoil layer for sod
The height of the topsoil layer for a rolled lawn differs slightly. The reason for this is the height of the sod. Ready turf is not sown and is already delivered as a grass probe. It is on average two centimeters thick and is laid directly on the ground. The thickness of the sod must be subtracted from the total height of the topsoil layer, so that in the end the lawn is not higher. That is, you need a layer of topsoil for the finished lawn only 13-18 centimeters.
Calculate volume and weight
The required amount of topsoil can be easily determined by the volume of the layer. This example assumes a lawn with the following dimensions:
- Depth: 15 cm
- Length: 5 m
- Width: 2 m
You can easily determine the volume using the following formula:
- Length in m x Width in m x Depth in m = Volume in m³
- 5 m x 2 m x 0.15 m = 1.5 m³
Now you know the volume of the topsoil layer. In order to now determine the required amount of soil from this value, you must first know the weight per ton. Topsoil weighs on average 1.3 tons per cubic meter. Depending on the supplier, this value may vary a little. You then calculate the total amount as follows:
- Volume in m³ x 1.3 t/m³ = Quantity in t
- 1.5 m³ x 1.3 t/m³ = 1.95 t topsoil
Tip: As a precaution, add 2 to 5 percent to the total amount. This will leave enough soil for later compaction, as it will reduce the actual height of the layer.
Frequently asked questions
Can topsoil simply be filled onto existing lawns?
No, this method is not recommended. Although it allows for a straight surface, the disadvantages still outweigh the advantages. The biggest problem is weeds. Weeds multiply rapidly due to the nutrients in the topsoil, making lawn care much more difficult. You need to scarify the old lawn beforehand to reduce the amount of weeds.
What is the best way to spread topsoil?
Depending on the area, different utensils are available: shovel, rake or mini-excavator. The mini-excavator is used primarily for larger lawns. If you do not want to put a lot of muscle power into the project yourself, you should hire a company. This is much faster, but is associated with higher costs.
What to look for when spreading the topsoil?
Since the topsoil is used as the foundation for the lawn, the surface must be as level as possible. Uneven surfaces or holes make for a sloping surface that is difficult to repair afterwards. For this reason, the subsoil should be straightened and compacted. Simply fill in any holes.
Does the soil need to be prepared?
The nutrient-rich soil should be freed from components such as stones, roots and the like before use. This will make it easier to straighten the soil. At the same time, the root growth of the lawn will not be inhibited by the components, which will ensure lush greenery in the garden.