What are the characteristics of a solar fastener?

Solar Guidebook – Part 4

The EJOT solar fastener is a stainless steel fastening element for fixing solar installations on roofs covered with trapezoidal profile sheets, sandwich panels and corrugated fibre cement sheets. It is a two-part fastener. Two-part, as the solar fastener is composed of a lower part, the screw, and a welded-on upper part, the set screw.

Depending on the substructure of the roof, the lower part is either an EJOT self-drilling screw JT3-SB-3-8.0 x L or an EJOT self-tapping screw JA3-8.0 x L or JA3-10.0 x L based on DIN 571. In both cases, the upper part of the solar fastener is a set screw M10 x L. The lower part of the solar fastener is fixed into the substructure, while the upper part is used to attach the fixing rails of the solar installation.
Vergleich Solarbefestiger mit ORKAN-Kalotte vs. FZD
In order to prevent any leakage on the roof due to the roof perforation, the solar fastener is either combined with an EJOT ORKAN storm washer and a E16 sealing washer or a fibre cement sealing element. The choice of whether to use an ORKAN storm washer or a fibre cement sealing element depends on the roof covering. The hex nuts including the washer on the set screw are used to fix the attachment or the mounting rails. EJOT supplies the “SB flat steel” as a possible adapter.

One key advantage of the solar fastener is that all tensile and compressive forces are transferred directly into the substructure. The use under construction law is regulated by ETA 22/0762 (only in combination with storm washer). The force resulting from the dead load of the solar system on the solar fastener is absorbed by its clamping and transferred to the substructure. The loads caused by wind, snow, net weight, etc. should not be underestimated. Specifically, elevated systems can provide the wind with a surface that mimics a sail, making them susceptible to its force. Once in a century events like storms Kyrill, Lothar and Wiebke are on the increase. With the solar fastener, you can be sure that the investment in your solar system is securely anchored to the building despite the next storm warning, which is sure to announce speeds of over 200 km/h.

Which version of the solar fastener is used for which application?

The selection of the right solar fastener depends, amongst other things, on the substructure. As a general rule, the solar fastener with the JA thread (self-tapping screw) must be used for a timber substructure. The solar fastener with the JT thread (self-drilling screw) has to be used for a steel substructure. It is worth mentioning at this point that the EJOT JT3-SB solar fastener can be mounted up to a thickness of 3 mm without pre-drilling.
To determine the correct screw length for the solar fastener, it is necessary to differentiate between the JA3 solar fastener for timber substructures and the JT3 solar fastener for steel substructures.

What are the benefits of the solar fastener?

The solar fastener is available for both timber and steel substructures. The strength of the solar fastener lies in the design of the screw head as a fixed attachment point and in the resulting permanent tightness. The fixed attachment point is defined by the screw head of the lower part. The screw-in depth is therefore always identical, ensuring a uniform mounting height. Due to the screw head as a fixed attachment point, the sealing element used (sealing washer and storm washer or fibre cement sealing element) also remains in the intended place and guarantees the tightness of the connection.
If it is not structurally possible to centre the profile rails of the mounting structure on the threaded pins of the solar fastener, special connection plates ca be used. The adapter plate, the “SB flat steel”, is attached using hexagon nuts. The profile rails can be positioned and mounted accordingly via a slotted hole in the adapter plate. When using “SB flat steel”, it is important to note that the eccentric load creates a bending moment that must be absorbed by the solar fastener. For structural reasons, the “SB flat steel” should ideally be installed in the direction of the roof ridge.
Falls der Solarbefestiger auf einem Dach mit einer Eindeckung aus Metallprofilen oder Sandwichelemente installiert werden soll, ist dieser zusammen mit einer entsprechenden ORKAN Kalotte zu verwenden.
If the solar fastener is to be installed on a roof with a cover made of trapezoidal sheet metal or sandwich elements, the solar fastener must be used in conjunction with an ORKAN storm washer. EJOT storm washers are made of aluminium and have an EPDM seal on the underside. In combination with an E16 sealing washer, they guarantee the tightness of the attachment point in the crown on the roof. In addition, the storm washer ensures that the pressure forces acting on the trapezoidal sheet metal or sandwich element are distributed. The storm washers are available from EJOT for all common trapezoidal and corrugated sheet metal geometries and can be painted in various RAL colours as required.

The next and final part of the solar guidebook examines the other fastening elements used in the construction of solar installations. Which products are used to connect the individual mounting elements, and what should be considered in detail when selecting the correct screw?

EJOT® Product recommendations for solar


Solar Fastener set JT3-SB-3-8.0xL with E16 + ORKAN storm washer

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Solar Fastener set JA3-SB-8.0xL with E16 + ORKAN storm washer

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Products for roof systems

Products at a glance