To ensure that a terrace is level and lasts for a long time, the coordinated substructure is crucial. With the correct procedure, this can be created comparatively easily.
What differences do I have to pay attention to in terms of the subsurface?
Whether the subsurface consists of earth or an existing concrete bed, whether it is level or uneven, has a major influence on the structure of the substructure and the materials required.
The main distinctions are:
- Grass, lawn and soil
- flat concrete substrates
- uneven concrete foundations and substrates
- Flat roofs
Instructions for grass, lawn and soil
If the subsoil is comparatively soft, an appropriate foundation must be prepared. The following utensils are required for this:
- Folding rule
- Bars
- line
- Spirit level
- Plate compactor
- Mini excavator
- gravel
- gravel
- Weed control
- Rubber granulate pads
- Foundation stones, strip foundations or exposed aggregate concrete slabs
- Fixing depending on the material
- spade
If these tools and materials are ready, proceed as follows:
1. Stake out the area
To get a straight outline, the area should be measured, the corner points marked with sticks and a cord stretched between them. This provides an orientation that enables precise work.
2. Calculate the slope
Before digging the earth for a foundation, the necessary slope should be calculated
will. The terrace should have a gradient of two percent starting from the house. This means that there should be a height difference of two centimeters over a length of one meter. This ensures that water can drain off easily and is not dammed up.
3. Dig out the earth
The top layer of earth is excavated to a depth of between 40 and 80 centimeters. The use of a mini excavator is particularly recommended for larger areas or solid earth.
4. Solidify the soil
The subsurface can be consolidated using a vibrating plate. This prevents the terrace from sinking and shifting. After the solidification, the slope should be checked again.
5. Fill in crushed stone and gravel and solidify
As a first layer, depending on the depth of the excavated area, 25 to 65 centimeters of gravel is poured into the pit. These are compacted and solidified with the vibrating plate. Then a 15 centimeter high layer of gravel is placed on the gravel and compacted again with the vibrating plate.
6. Lay the fleece
Weed control prevents unwanted plants from growing through the gravel layer. As a layer on top of the stone layer, it therefore provides good protection and reduces it in the long term
necessary maintenance effort.7. Lay foundation stones, strip foundations or exposed aggregate concrete slabs
Whatever the choice, the material for the substructure should always be selected to match the terrace material.
8. Bring in padding
Before the substructure is placed, rubber granulate pads should be placed. These also serve as insulation, which extends the durability of the substructure and the terrace slabs.
9. Place the substructure
The substructure is placed on top and screwed to the base. It is important that the appropriate distances are maintained. The manufacturer's instructions must be followed here.
10. Put on the decking
Finally, the terrace slabs or planks are laid on and screwed to the substructure or connected with a click system.
Tip: Renting a mini excavator and vibrating plate is recommended for the work. This is possible, for example, at various hardware stores.
Flat concrete
An already level and undamaged concrete substrate can be used very easily for the terrace construction. However, a few steps are necessary to prepare it accordingly.
It refers to:
1. Thorough cleaning
Before any further steps are taken, the surface must be cleaned thoroughly. The use of a Kärcher, for example, is suitable for this.
2. Mending
After the concrete is completely dry, it should be carefully checked for damage such as cracks, bumps and holes. A repair if necessary is necessary as a basis.
3. Surveying and drilling
The distances between the individual panels or strips are measured and marked on the concrete. Then, if required by the selected system, the holes can be made.
4. Take the gradient into account
Especially with older concrete substrates, it may be possible that the necessary slope is not available. The required height difference can be created using so-called adjustable feet or adjustable terrace bearings. The substructure is now attached to these adjustable feet. Another measurement ensures that the terrace is two percent away from the house later
falls off and the water can drain off easily.5. Application of the floorboards
Depending on the system in question, the terrace slabs can now be laid or the planks screwed together.
Uneven concrete foundations and substrates
It is ideal if the existing subsurface is level before the substructure and the terrace are installed. Therefore, it makes sense to either excavate a foundation or to level out any unevenness on the concrete. This can be done, for example, by the following steps:
- Clean concrete
- Roughen concrete
- Build the frame
- Pour and smooth out new concrete
- After drying and hardening, build the substructure
However, this procedure is not always possible. If it cannot be implemented, various options are available. Including:
- Backfill with rubble and gravel with subsequent solidification
- Remove soil or concrete, consolidate with a vibrating plate and pour on gravel, rubble and concrete
- Use of adjustable feet
Tip: If you have little experience, it makes sense to call in an expert advisor. Even if this seems expensive at first, it can save money in the long term and effort in the short term.
Laying on foil and flat roofs
Areas that have already been foiled or flat roofs represent another category of subsurface. There are two peculiarities with these. On the one hand, a closed frame has to be built. Otherwise the substructure has to be screwed directly onto the roof or the foil. However, this has some significant disadvantages and in some cases is not even possible.
On the other hand, a layer of weed fleece or PE film should be laid when installing on flat roofs. This prevents a chemical reaction between the surface and the rubber granulate pads.
Note: The rest of the procedure is the same as for a concrete substrate. All that needs to be done is to prepare more in order to add a frame to the substructure and, if necessary, to lay out a foil beforehand.