Foundation for your patio roof: expert tips ✓
Grayson Whitaker
To be on the safe side, a pergola needs a stable foundation. You can find out in this blog which types there are and which is the right one for your PERGOLUX pergola.
Why is a good foundation important?
A professionally correct foundation provides a stable, level surface for your pergola. This not only makes assembly easier, but also ensures the required stability of the pergola. If you install your pergola on a sloping surface, it will be subjected to unbalanced pressure for which it was not designed.
This may have consequences:
- The pressure on the screw connections is too high and this can lead to damage.
- The integrated gradient may be negatively influenced, meaning that the water cannot drain away properly.
- Accessories, such as screen blinds, cannot be installed correctly.
It also has visual disadvantages - who wants a crooked pergola?
Is a foundation mandatory?
Pergolas are available in different sizes and weight classes; it is often not clear whether a foundation is absolutely necessary or, for example, a compacted ground with a layer of gravel and terrace slabs on top is sufficient. In any case, it is advisable to know the building regulations that apply to the planned building site Our pergola apply.
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Building regulations:
The respective state building regulations of the federal states occasionally stipulate whether and when a garden house needs a foundation. Unfortunately, these regulations vary from state to state. You can obtain information from your local building authority, which will also provide information about any regulations in the municipal development plans. (See also our guide on building permits).
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Club statutes:
Allotment garden associations also have precise regulations regarding foundation construction. Even if you don't find anything about this in the lease or statutes, you should contact the board and ask to be on the safe side!
In some cases a foundation is not necessary. This would be the case if you have already built your terrace on a foundation and can therefore ensure optimal fastening of the pergola, for example with anchor bolts (expansion bolts).
Plan the foundation
Check the surface
The surface condition plays an extremely important role and should be checked first. Is it pure, solid topsoil or perhaps loose, sandy soil? Is the subsoil possibly riddled with roots that make it difficult to build the foundation?
To do this, simply do a test excavation to be sure!
Leads
Do you perhaps need electricity and water connections in your pergola for, for example, an outdoor kitchen, lighting or heating?
- The empty pipes required for this should be integrated during the construction of the foundation. Except for point and strip foundations, they can be retrofitted.
- Consider whether you will need to carry out this work yourself or perhaps hire professionals.
Size
To specifically plan the foundation, draw the dimensions in the floor plan of your future PERGOLUX pergola. It is also possible to obtain a foundation plan for the respective model in advance. This means you can build the foundation in advance and don't have to store the pergola for a long time.
Foundation type
Depending on the given requirements, different foundation variants are possible.
- For small pergolas, a slab foundation made of path slabs is often sufficient
- For larger models it should be point or strip foundations
- On unsafe ground, a continuously closed concrete slab is recommended
- If the soil has good load-bearing capacity, a screw foundation, which can be built comparatively quickly, is ideal
In the following section we will discuss the different types of foundations.
The foundation made of path slabs
A foundation made of path slabs is the simplest option. It can be built with little effort and is sufficient for small pergolas.
Path slabs are available in different sizes, e.g. 30x30, 40x40 or 50x50 cm, and are several centimeters thick. However, they cannot tolerate large point loads; they would then simply break. To ensure that the panels are stable and straight, a deep pit must first be dug; 30 cm should be enough. This pit must then be filled with a layer of gravel and gravel. The individual layers should first be compacted, only then do the path slabs follow. The last step is to slurry with sand so that the joints between the panels are tight.
- Advantage: built quickly, relatively low cost
- Disadvantage: only suitable for lighter pergolas
The strip foundation
The strip foundation is so called because only approximately 40cm wide concrete strips are poured onto which the pergola can be attached. If built correctly, it is sufficient for even the largest pergola models, but requires enormous effort.
To ensure that the strip foundation is frost-proof, the trenches must be at least 80cm deep. A mini excavator would be very helpful here! To prevent the trench walls from collapsing, it is helpful to support them with formwork boards before the trenches are poured with concrete.
If the subsurface is not stable enough, we recommend installing an additional 10cm thick concrete slab - on top of compacted gravel and a PE film.
- Advantage: very stable, frost-proof, relatively little concrete is required without a slab
- Disadvantage: extremely high workload, construction machinery required
The concrete slab as a foundation
A closed concrete slab provides an absolutely stable base for the pergola. However, the construction is quite labor-intensive and involves high costs. This variant is only really necessary in unstable, loose soils or in swampy areas near bodies of water.
This type of foundation is also sometimes chosen where it would not be absolutely necessary because the construction appears to be easier than a strip or point foundation. However, very large amounts of fresh concrete are required here, which you don't want to mix yourself.
Before you can pour this foundation, preliminary work is necessary. First, a 40-50cm deep pit must be dug the same size as the pergola - with some allowance for the formwork. The ground must be straightened and compacted. The walls must be supported with robust formwork boards because several tons of weight are involved.
This is followed by a 15cm thick layer of gravel, which also needs to be straightened and compacted. A vibrating plate is essential here.
A thick PE film then follows the gravel so that the concrete is protected from moisture from below.
Only after these steps can the fresh concrete be poured. The concrete is applied in two layers. Steel mats (reinforcement) are placed between the layers for stabilization. Finally, the concrete is smoothed out with the scraper.
- Advantage: maximum stability, very useful on unsafe surfaces
- Disadvantage: enormous amount of work, very high costs, construction machinery is absolutely necessary
The point foundation
A point foundation requires significantly less concrete than a concrete slab or a strip foundation. It consists of several "point-shaped" individual foundations that are erected at equal distances under the pergola columns.
Although you save a lot of material here, this variant is only suitable for solid, load-bearing floors. If the soil is too loose, the weight of the pergola may move it because they are not connected to each other.
Although material is saved, great precision is required when measuring, excavating and cladding the individual foundations. Cladding the individual foundations with formwork boards is an effort that should not be underestimated. A small “do it yourself tip” at this point would be to use sturdy pipes with a correspondingly large diameter as formwork. Once everything has been prepared, fresh concrete is poured into the formwork or pipes. The amount of concrete required can still be managed with ready-to-mix concrete from the hardware store.
- Advantage: comparatively little material and therefore correspondingly lower costs
- Disadvantage: not possible on loose soil, very high accuracy when measuring is required.
We have now explained the different variants of foundations. But what type of foundation is suitable for a pergola with a slatted roof?
Our recommendation for the PERGOLUX pergola
In order to achieve the maximum wind load, we recommend setting reinforced point foundations measuring 85x85x85cm and connecting these with a strip foundation. The pergola can then be attached to the foundation through the terrace covering using so-called anchor bolts (expansion bolts).
Alternatively, you can also screw the pergola onto smaller sized foundations such as 40x40x75cm or directly into patio coverings such as stone slabs or wooden floorboards. A lot of customers do this and the maximum wind load depends somewhat on your circumstances
Here you can find the foundation plans for the PERGOLUX Pergola S1. The foundation plans for our S2 models can be found directly on the product page under “Dimensions and technical details”.
3x3m PERGOLUX Pergola S1
3x4m PERGOLUX Pergola S1
4x4m PERGOLUX Pergola S1
4x6m PERGOLUX Pergola S1
FAQ
How much does a point foundation cost?
The costs for a point foundation are usually between 150 and 400 euros per foundation point, depending on the material, size and workload. The material costs for concrete or precast concrete are around 30 to 80 euros, while the labor costs can vary between 100 and 300 euros depending on the effort.
Which diameter should you choose for a point foundation?
The diameter of a point foundation depends on the load it is intended to carry and the soil conditions. As a rule, a diameter of 85x85x 85cm is recommended for lighter structures such as carports, terraces or garden sheds.
At what distance do I place a point foundation?
We recommend a point foundation for each post of the pergola. Some models (such as 4x6m) have 6 posts and other models (such as 4x6m wall mount) have only 3 posts.
Do pergola posts have to be anchored in the ground?
Yes, pergola posts must be anchored in the ground to ensure stability and stability. We recommend fastening with expansion anchor bolts for point foundations with a length of at least 13 cm.
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