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Paving is considered to be a durable and uncomplicated building material for terraces, garden paths and parking spaces. With the right substructure, the evenness and height of the pavement are retained over the long term. Our guide will show how to do it.
In a nutshell
- Paving with a frost-proof substructure remains flat even in frost
- the substructure does not settle later due to the compaction
- typical materials for the structure of the base layer are mineral concrete, KFT or what is known as a preliminary screen
The right structure
In order for your pavement to actually be resilient and to withstand changing environmental conditions such as moisture, dryness, heat and frost, the right structure is important. The substructure, which creates the basis underneath the actual paving, is of elementary importance. It should meet the following requirements:
- Safe drainage of rainwater and waterlogging (due to freezing standing moisture in the ground)
- Derivation of the loads from the paving and its use in the natural subsoil
- Dimensional stability without settlement under load and changing environmental conditions
In order to implement these requirements correctly, the existing floor is usually replaced with a suitable material. This is installed to a depth of around 80 centimeters and founded on natural, load-bearing soil. Although this base layer is already being installed, there is still a fine subgrade on the top, which ultimately creates the real level for the subsequent paving.
Notice: The depth of 80 centimeters for the substructure leads to a soil zone that is normally no longer reached by frost in Germany. In this way, rising and falling due to freezing and thawing soil moisture, together with its effects on the pavement, is reliably prevented.
The material
So that the substructure under the pavement can really do what it is supposed to do, you have to choose the right building materials. It must:
- be compressible
- produce no capillary action
- Drain water underground
You can achieve this primarily with quarry, i.e. gravel. From a technical point of view, there are different "types" that differ in their properties, but are all suitable for installation under paving:
- gravel
- KFT (combined frost protection and base course)
- “Pre-screen” (heterogeneous gravel before screening into individual grain sizes)
- Mineral concrete (crushed stone mixture that gains strength exclusively through compaction)
You also need fine grit, from which you can then produce the fine subgrade, i.e. the actual laying layer, for your pavement.
Notice: The exact grain size of the quarry used, i.e. the size of the individual stones, is less relevant for a paving surface. Make sure, however, that the materials are specified by the manufacturer, i.e. the quarry or building materials dealer, as being compactable.
The tool
With just a few tools and a small amount of machinery, it is possible to provide your pavement with a technically flawless substructure.
- Shovel, spade, pickaxe
- optional: mini excavator (for large paved areas)
- wheelbarrow, bucket etc.
- garden rake
- Vibratory plate, motor driven
- setting bar
- level
- meter rule, measuring tape
Notice: Other equipment and vehicles for treating your excavated earth and bringing in the necessary rock material is not listed here. Depending on your own possibilities, a company can be commissioned here or the delivery can be made free of charge.
The instruction
Now start to build up the substructure step by step to hold the patch:
Step 1 - determine the altitude
Before you start with the actual work, you should determine the future upper edge of your paving and its substructure. Each paved area should have a slope of around 1 to 2 percent, ideally away from buildings. If you have decided on the highest point, use the following calculation method to determine the height of the substructure, starting from the top edge of the pavement:
- top edge of pavement
- Thick pavement
- 2 centimeters for fine planum
- = upper edge of base course
Ideally, mark the height on a house wall or a hammered wooden slat along with the information by how much lower the upper edge of the base layer should be from this marking.
Step 2 - Excavate
The first practical step is to create the excavation, i.e. the pit, for the frost-proof and stable substructure of the pavement:
- Mark out the outer edges of the paved surface
- Allow 80 centimeters on all sides
- Cut off and remove lawn sods etc
- Loosen the topsoil (humus layer, usually approx. 20 to 30 centimeters thick) and use it in the garden
- loosen and dispose of underlying earth material
- Excavation depth up to 80 centimeters below ground level
Notice: The excavation depth does not depend on the height of the subsequent covering! The depth reached in relation to the surrounding terrain is always decisive.
Step 3 - Install in layers
Now, layer by layer, the core of the substructure is created in the created pit:
- Bring in gravel, KFT or similar and level with a rake
- Height per layer maximum 30 centimeters
- Compact the material with a vibrating plate evenly and over a large area until there is no more movement when the vibrating plate is driven over
- Slope the structure upwards at the side at a 45° angle
- Install excavation above embankments up to the top edge of the ground
Step 4 - Make the slope
When you reach the top of the gravel structure, it's time to shape your pavement later:
- Bring in the last layer of gravel and level
- From the determined high point of the substructure, use a leveling batten and spirit level to remove the gravel
- Ratio: With a gradient of 2 percent per meter away from the high point = gaining 2 centimeters of depth
- Compact the last layer and check the height
- if necessary apply a new layer on the incline to the target height
Tip: Fix your spirit level to the leveling board with adhesive tape. Place the spirit level on one side so that the leveling batten has the correct gradient (e.g. with a length of spirit level 1m and a gradient of 2%, 2 centimeters on one side). Now you can control the inclination directly when pulling off.
Step 5 - The Fine Planum
Finally, with a fine subgrade made of fine split, you ensure a really level surface on which you can lay the paving stones directly:
- Add fine split to compacted gravel and spread about 2 centimeters thick
- Level with a leveling board to even out any unevenness
- Check the gradient with a spirit level
Done - you've done it, the substructure of your pavement is in place. Now nothing stands in the way of the actual paving work.
frequently asked Questions
Can gravel also be used as a building material?Instead of crushed stone and other broken mineral materials, gravel is often brought into play as a foundation material. Since the individual pebbles are round, however, they can only be compacted to a limited extent. Gravel is therefore at most possible as an additive to other substances, but ideally it should even be avoided.
Can I do without the fine planum?Theoretically, execution without fine subgrade is possible under paving. However, it usually fails because the coarse components of the frost-proof substructure do not allow for the levelness that would be necessary for the later paving.
Why do I need a frost-proof substructure?If coverings are laid on natural soil, they rise and fall with changes in the soil. Natural soil contains water that ebbs and flows and also freezes. Since all this does not appear uniformly, your paved surface will sooner or later become a mogul slope without the appropriate substructure.