The correct fastening of photovoltaic structures on metal roofs is essential to guarantee the stability and durability of a solar installation. In this context, choosing between self-tapping and self-drilling screws is fundamental, as each type of screw responds to specific structural and environmental needs.
In this article, we will analyse the determining factors for selecting the right fastening for photovoltaic installations on metal roofs, detailing in which cases self-tapping or self-drilling screws should be used.
Factors to take into account when choosing a fastener for solar panels
Before choosing the right type of screw for fixing photovoltaic structures on metal roofs, it is important to analyse the following aspects:
- Type of installation: co-planar or triangular
Depending on the arrangement of the PV modules, the forces affecting the fastenings vary.
In coplanar installations, the fastening must withstand lower forces, which allows for simpler anchoring options. In triangular installations, the anchors are subjected to higher wind and weight loads, requiring more robust fixings. - PV installation conditions
The conditions of the installation, such as its location and height, influence the stresses to which the fastening will be subjected.
The higher the height of the installation, the greater the exposure to wind and therefore the greater the structural requirements. Likewise, the closer an installation is to the sea, the greater the stresses. - Type of metal roof and substructure
At this point, the compatibility of the fastener with the metal roof and its substructure must be taken into account.
If the fastening is done directly on the deck, self-tapping screws can be used, because the flashings do not allow this type of installation.
On the other hand, if the deck has a metal substructure (such as rafters), self-drilling screws are recommended, as they offer greater strength. - Condition of the metal roof
If the metal roof is in poor condition, it is not advisable to install photovoltaic systems. If there is any doubt about the condition of the roof, the only possible solution is to fix it directly to the substructure, which is the structural element.
When should self-tapping screws be used in photovoltaic installations?
The use of self-tapping screws is recommended in the following cases:
- Coplanar photovoltaic installations, where the stresses to which the structure is subjected are lower.
- Installations protected from external factors, such as wind or snow, thanks to adjacent buildings or other elements that act as barriers.
- Fastenings made directly on the metal roof.
When should self-drilling screws be used on metal roofs?
In the case of self-drilling screws, it is recommended to use them in the following scenarios:
- When the installation is exposed to heavy wind or snow loads, which require a stronger fastening.
- When the structure needs to be anchored to the metal substructure (beams), which provides greater stability.
The choice between self-tapping or self-drilling screws for fastening solar panels to metal roofs depends on factors such as the type of installation, the location, the environmental conditions and the roof structure.
Taking this information into account is an important point in choosing the right fastening system that will guarantee a safe, efficient and long-lasting installation for any photovoltaic project.
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