Practically all photovoltaic installations in Brazil are carried out on 3 types of surfaces: roof, slab or ground. In each of them there are points that are more susceptible to doubts, and in this article we will go into detail about the construction of the footings for slab fixing structures.
We know that the action of winds is much more intense in PV structures installed on slabs, compared to systems located on roofs.
The reason is simple: the exposure of the s to the wind is greater and more direct on slabs, as they are not arranged flush with the roof. Furthermore, the buildings are taller, as they are residential or commercial buildings with several floors.
Therefore, the fixing structure must be further reinforced, and it is necessary to guarantee minimum ballast so that the installation remains anchored, avoiding losses and accidents.
The most common way to keep the PV system anchored is through the construction of concrete shoes to fix the structures, but many doubts may arise in this process, so we created a step-by-step guide to help with this step, but first we have some considerations:
- Avoid applying mechanical anchors directly to the slab, to avoid problems related to the slab's resistance and waterproofing;
- Respect the distance from the edges indicated by the structure manufacturer;
- If the installation is in a location where the relief favors the emergence of large wind currents, such as slopes and ridges, consult the structure manufacturer;
- Consider carrying out a small construction to serve as a wind barrier if the installation location is as described above;
- Ensure a corridor approximately 40 cm high for wind flow at the bottom of the s;
- Use structures made of antioxidant materials, such as aluminum and stainless steel;
- Always follow the structure manufacturer's installation manual.
Having made the considerations, we proceed to the construction of the footings. The method indicated below consists of constructing a small concrete footing, chemically anchored into the slab.
- Use 25x25cm hexagonal blocks, 8cm high, or build the shoes using wooden molds with the following minimum internal dimensions: Width = 20 cm; Depth = 20 cm; Height = 15 cm
Fill the mold with concrete and wait for drying time (recommendation: 7 days). After the curing time, remove the shoe from the mold.
- Mark the positions where the shoes will be glued to the slab.
- Slab waterproofing: the waterproofing must be removed from the areas where the footings will be installed, to ensure the correct application of the chemical glue.
- Install the footing on the slab using an Epoxy-based chemical adhesive. We recommend Compound Adhesive – Vedacit, types MF or TIX, which in addition to fulfilling the function of a chemical anchor, also has a waterproofing function.
Important: consult the chemical glue manufacturer's application manual, which lists the application surfaces and the ideal drying time, which must be respected before going to the next step.
- With a drill, using a concrete bit, pre-drill a hole in the center of the top face of the footing.
- Position the base of the metal structure on the shoe and install the parabolt to the depth indicated by the manufacturer.
- Complete the installation of PV structures and s.
If for some reason it is not possible to follow the method described above, you can also build heavy footings without applying chemical adhesive, or even fix the parabolts directly to the slab, but these are methods more subject to inconveniences, such as excess weight, reduction of the slab area, waterproofing failure, among others.
If it is necessary to follow these or other methods, consult your structure supplier, and that the Solar Group technical team will always be here to help you!
