In February 2022, Eternit published a guide for the proper installation of corrugated sheets. The recommendations are aimed at planners and installers who cover roofs with fiber cement corrugated sheets. The installation instructions define minimum distances, suitable fastening materials, and sealing types for various substructures made of wood and steel. The core of the guide is specifications for the statically correct arrangement of fastening points and material-appropriate selection of screws and mushroom seals.
Static requirements: at least four fastening points per sheet
The Eternit corrugated sheets are fastened on the corrugated ridge. For static reasons, the first corrugated ridge may not be used for fastening. Each sheet must be secured by at least four fastening points to ensure adequate stability. The arrangement of the fastening points depends on structural factors such as location, terrain profile, and building structure and must be adapted according to local loads.
The distance of the fastening points from the sheet edge must be at least 50 mm. For sealing, plastic mushroom seals with steel inserts are required. The steel insert ensures the necessary dimensional stability and pressure distribution when fastening on fiber cement corrugated sheets.
Which fastening points for wood and steel purlins?
The choice of fastening point depends on the material and condition of the substructure. For wooden substructures, Eternit recommends wood screws. Self-drilling variants allow installation without pre-drilling the corrugated sheets or the substructure. If standard wood screws according to DIN EN 14592 are used, pre-drilling of the corrugated sheets is required.
For wooden batten substructures, self-drilling screws with stainless steel washers must be used. The support battens must have a minimum cross-section of 60 × 60 mm to ensure the required screw insertion depth. For large rafter spacings, wood coupling purlins are required, which must meet the same fastening conditions as classic wood purlins.
For substructures made of steel, the manufacturer recommends self-drilling screws with corrosion protection made of bimetal. Eternit offers special drilling fasteners that are suitable for sheet thicknesses of 2.0 to 5.5 mm for steel and 3.0 to 5.0 mm for aluminum. A key safety note is: fastening points must not be driven through the corrugated sheets. This requirement aims to prevent microcracks and risk of breakage in the fiber cement.
Special case Berlin Wave: colored bell screws with pre-drilled holes
Different requirements apply to the Eternit Berlin Wave. Here, colored stainless steel bell screws with sealing washer are required. The corrugated sheets are fastened on the second and fifth corrugated ridges through pre-drilled holes. The bell screws allow optically matched installation and prevent the formation of stress cracks from drilling on the construction site through the pre-drilled holes.
Practical tips: left and right coverage, corrugation ridge counting
To determine the corrugated ridge for fastening, Eternit provides specific counting rules. With left-hand coverage of the corrugated sheets, counting begins from the right corrugated ridge. With right-hand coverage, counting is done from the left side of the corrugated sheets. This convention prevents confusion on the construction site and facilitates coordination between planning and execution.
Sizing recommendation and planning basics in the download center
Eternit offers non-binding sizing recommendations that address the specific conditions of the construction project. Detailed information on planning and execution is available in the manufacturer's download center. The planning basics contain detailed specifications for load assumptions, anchoring distances, and required cross-sections of the substructure.
Classification: Code-compliant fastening as a prerequisite for durability
The fastening of fiber cement corrugated sheets follows specific physical requirements. Fiber cement is a brittle material that can only take up limited tensile stresses. If the sheet is locally overloaded by impact fastening or uneven pressure distribution, microcracks can form that lead to spalling during freeze-thaw cycles. The mushroom seals with steel inserts required in the guide distribute the screw pressure over a larger surface and prevent pressure peaks.
The requirement not to drive fastening points through the sheet is material-specific: Unlike trapezoidal sheet or bitumen corrugated sheets, mechanical impact stress in fiber cement causes irreversible structural damage. The recommended self-drilling screws with mushroom seal are therefore not just a comfort feature but a technical necessity.
Comparison with other roofing materials
Compared to metal roofing sheets such as trapezoidal sheet, fiber cement corrugated sheets require greater care in fastening. While trapezoidal sheet tolerates local overloads thanks to its ductility, fiber cement is sensitive to point loads. There is also a difference compared to roof tiles: these are held primarily by weight and wind clamps, while corrugated sheets are connected to the substructure by force fit.
The required minimum cross-sections of 60 × 60 mm for support battens are in the upper range of common timber frame construction cross-sections and require careful coordination with rafter spacings during execution planning. For steel substructures, Eternit's special drilling fasteners offer advantages over standard drilling screws because they are matched to the hardness and sheet thickness of steel and aluminum profiles.
Conclusion: Technical precision instead of improvisation
Eternit's guide emphasizes the need for material-appropriate processing of fiber cement corrugated sheets. The detailed specifications for fastening points, seals, and minimum distances reflect the physical limits of the material. For planners and installers, the guide provides clear guidance – code-compliant implementation is a prerequisite for the durability and safety of the roof structure. The free planning basics in the download center supplement the brief instructions with static calculation approaches and material-specific parameters.
