Roof metal deck fixing: comparison of nails and screws​

This article addresses the methods used to fix a metal deck to a steel base material in roofing systems, specifically focusing on two scenarios: (i) uninsulated roofs and (ii) insulated roofs, as illustrated in Figure 1.

Figure 1 - Fixing of a metal deck in a roof: uninsulated roof (left) and insulated roof (right).

The comparison focusses on two of the most common methods to fix decks in these roof systems under typical European design practice: (1) powder-actuated fasteners (PAF) considering the Hilti X-ENP-19 and X-ENP2K models (shown in figure 2) and (2) screw fasteners, in which the models analysed are Hilti’s S-MD 63S, S-MD 65S, S-MD 23Z, and S-MD 25Z. By selecting these fasteners, the comparison covers a range of options suitable for both thin base materials, such as purlins, and thicker structural elements like I or H steel profiles.

Figure 2 - Traditional ways of fixing elements to steel: welding (left) and bolting (right).

Figure 3 - Some of the screw solutions to be compared: S-MD 63or S (left) and S-MD 25Z (right).

To effectively compare the two technologies, several technical fields were considered. The assessment includes the following categories:

• Base Material: Evaluation of compatibility and performance with various substrates.

• Loads: Analysis of how each technology handles different load conditions.

• Corrosive Environments: Consideration of resistance to environmental factors that may cause deterioration.

• Approvals: Review of regulatory and certification requirements met by each solution.

• Fatigue: Examination of the durability of each technology under repeated stress cycles.

• Seismic: Assessment of the performance in seismic conditions.

In addition to the technical comparison, a value engineering optimisation and a total installation time analysis is conducted. This analysis provides a productivity perspective by comparing the total installation times associated with each solution.

The information provided in this article is non‑binding, for general information only and does not replace a project-specific structural design. The responsible designer or structural engineer must always verify the suitability of the chosen fastening solution, including compliance with local regulations, applicable approvals (e.g. ETAs, ICC‑ES reports) and the project‑specific actions such as wind or seismic loads.

Base material

Both screw and nail solutions provide options for fastening to various types of base materials, including purlins (which are thinner base materials) as well as thicker I/H profiles.

For purlin applications, screws demonstrate versatility by accommodating thinner base materials. For instance, the S-MD 23 Z screw is suitable for base materials starting from 1 mm in thickness. In contrast, the nail solution (X-ENP 2K) is limited to base materials starting from 3.00 mm in thickness. When it comes to thicker base materials, screws can fasten into materials up to 15.00 mm thick. For example, an IPE 400 profile, which has a flange thickness of 13.5 mm, falls within this range. The X-ENP-19 nail, on the other hand, does not have a specified upper thickness limit.

Regarding the deck to be fastened, screws can be used with decks as thin as 0.40 mm, providing coverage for slightly thinner decks compared to nails, which are applicable from 0.63 mm thickness and above.

The number of deck sheets that can be fixed in a single operation is influenced by the technology used. Screws are constrained by their drilling capacity; for example, the S-MD 25 Z screw can handle a total thickness (base material plus all deck sheets) up to 15 mm. Nails, depending on the deck thickness, can secure up to four layers of sheets in one operation.

Both technologies provide similar compatibility with steel grades, effectively covering grades from S235 to S355.

A summary of these comparisons is presented in Table 1.

Table 1 - Comparison of nails and screws in terms of base material coverage.

Loads

Following the evaluation of base material compatibility for both screw and nail fastening technologies, their performance under load—specifically resistance to shear and tension forces—is assessed. This comparison considers the effect of base material thickness and groups the solutions according to their application: fastenings into thinner base materials such as purlins, and fastenings into thicker base materials like I/H profiles.

The analysis on purlins assumes the fixing of a 1.00 mm deck into a 3.00 mm thick purlin. In this scenario, both screws and nails demonstrate similar overall performance. Screws provide slightly higher resistance to shear loads, capable of handling up to 7 kN, compared to 6 kN for nails. Conversely, nails exhibit superior resistance to tension loads, achieving 6 kN as opposed to 5.48 kN for screws.

For applications involving thicker base materials, such as fastening into an 8.00 mm I beam, the evaluated X‑ENP‑19 nail shows higher characteristic shear and tension resistances than the S‑MD 25 Z screw for the example configuration considered.

Nails can withstand shear loads up to 6 kN, whereas screws are limited to 4.98 kN. The difference in tension resistance is even more pronounced, with nails supporting up to 8.00 kN, compared to only 4.00 kN for screws. This can be particularly relevant when only uplift wind loads are considered in the design, in which the fastening points are subjected to tensions forces primarily.

Table 2 presents a summary of these load performance comparisons for both technologies.

Table 2 - Comparison in terms of load resistance for both fixing into purlins and I/H steel profiles.

Corrosive Environments

When selecting fastening solutions for use in corrosive environments, it is important to consider the materials and design of the fasteners to ensure adequate durability and service life.

Stainless steel screws, specifically the S-MD 63 S and S-MD 65 S models, are engineered to withstand more aggressive outdoor environments. These screws are suitable for locations with moderate concentrations of pollutants and can offer an intended service life of up to 25 years, when used in the corresponding corrosion category, designed in accordance with the relevant approvals and installed according to the product instructions.

Nail solutions, on the other hand, are suitable for temporary exposure to outdoor environments, such as during construction, for periods up to six months. For long-term applications, nails are recommended exclusively for dry indoor environments where they also can achieve a service life of 25 years. A summary of the environmental suitability and expected service life for both screws and nails is provided in Table 3.

For uninsulated roof applications, where fasteners are exposed to external conditions, screw solutions are more suitable due to their enhanced resistance to corrosion. If nails are to be used in such scenarios, they must be complemented with a sealing cap (SDK2) as illustrated in Figure 4 to mitigate exposure to moisture and pollutants, and to extend their applicability to certain outdoor corrosion categories as specified in the product data sheet.

In contrast, for insulated roof systems where the fasteners are not exposed to external environments, both screw and nail technologies are appropriate choices.

Table 3 - Comparison in terms of environmental conditions and corresponding service life.

Figure 4 - SDK2 Sealing Cap for X-ENP nails.

Approvals

For non-standardised construction products, the European Technical Assessment (ETA) [1] provides an independent, Europe-wide evaluation of essential performance characteristics. This assessment ensures that products meet established requirements and can be reliably compared and specified across the European market.

In addition to the ETA, construction products may also be evaluated by other external organisations, such as the American Bureau of Shipping, Lloyd’s Register, or insurance companies specialising in fire protection systems, like FM. These entities offer additional layers of assurance regarding the product’s quality and suitability for specific applications.

When considering product approvals, both screw and nail technologies have obtained ETA certification. This contributes to building confidence in these products by demonstrating that their performance has been independently assessed for the defined intended uses and conditions stated in the respective approvals.

Notably, nail solutions, and particularly the X-ENP-19 model, possess a wider range of approvals from various regulatory and certification bodies, as detailed in Table 4. This broader scope of certifications highlights the versatility and acceptance of nail solutions in different regulatory environments and applications. Designers must, however, always verify that the intended use, base material, environmental conditions and installations parameters of the project are covered by the scope of relevant product approvals (e. g. ETA, ICC-ES, …).

Table 4 - Overview of Approvals for both screws and nails assessed.

Dynamic Loading

To ensure the fatigue strength of powder-actuated fasteners and fastening screws, dynamic pullover tests are conducted to evaluate their performance under cyclic loading conditions, such as those generated by wind forces. The characteristic pullover capacity for both fastener types is defined based on 5,000 load cycles—a threshold established as sufficiently conservative for wind load scenarios and validated by decades of practical experience [2]. These tests typically involve harmonically pulsating tensile loads at a frequency of 5 Hz, conducted at a minimum of three upper load levels. It is important to note that dynamic pullover testing is not mandatory.

If such tests are not conducted for powder-actuated fasteners, the potential impact of wind-induced cyclic loading must be addressed by applying a reduction factor of 0.5 to the design resistance, as specified in Eurocode 3 [3] and reflected in the EAD [4] as the coefficient α cycl.

For screws, the reduction for dynamic effects is handled differently: if no test data are available, a reduction factor of 2/3 is applied, as adopted in EAD [5] based on long-term German practice.

This reduction is already incorporated into the characteristic resistance published in the ETA for both nails and screws, so it does not need to be explicitly stated in design calculations.

This approach is intended to provide a conservative basis for designing powder‑actuated fasteners and screws for wind‑induced cyclic loading within the scope of the relevant European Assessment Documents and approvals.

Seismic Assessment

The current European Assessment Documents (EADs) for powder-actuated fasteners and fastening screws do not formally cover dynamic loading resulting from earthquakes.

However, a preliminary assessment of fastener suitability for seismic applications can be made by following U.S. provisions, such as those in ICC-ES AC70 [6]. In the U.S., both powder-actuated fasteners and screws have been used for decades as mechanical fasteners in steel deck diaphragms of non-dissipative structures [7], with seismic verification typically performed using substitute static loads. Experimental studies have shown that both technologies, especially powder-actuated fasteners, perform robustly under dynamic (seismic) loading, often outperforming arc-spot welds in terms of ductility and reliability [2].

During seismic events, the failure mode for these fasteners is generally ductile, with the sheet metal or fastener itself failing rather than the anchorage (into the base material). Cyclic load-displacement tests on steel deck diaphragms demonstrate that even with significant plastic deformation, the load peaks for each cycle remain within the range of monotonic reference curves, indicating stable and predictable behaviour – see Figure 5. This ductile response is essential for dissipative structures, and the Canadian standard already defines a behaviour factor for steel deck diaphragms, with similar provisions being considered for U.S. standards. To ensure ductile diaphragm behaviour, the design must account for the resistance of fastener anchorage at end overlaps, the shear resistance of screws at sidelaps, and the reliable transfer of diaphragm forces to vertical bracing or shear walls.

The suitability of powder-actuated fasteners or screws for seismic applications cannot be generalised and must be assessed on a product-specific basis. Designers should consult the relevant approvals and, where necessary, obtain project‑specific assessments. While U.S. experience points to generally good performance for both technologies under seismic loading, in Germany and other European contexts, project-specific approval may still be required for seismic verification.

Figure 5 - Cyclic load-displacement behaviour of steel deck diaphragms under seismic loading.

Value Engineering Optimisation

Beyond the technical comparison, a value engineering design analysis was conducted, considering all the parameters related to a specific application. For the analysis the following parameters were considered:

• A 5000 m

  ²

  roof project;

• No diaphragm design considered (only uplift wind load);

• Fixing into an IPE 200 profile (8,5 mm flange thickness);

• Comparison of X-ENP-19 nails with S-MD 25 Z (single screws, not collated);

• Wind uplift action of 3.0 kN/m²

  (factored as live load = 4.5 kN/m²)

• Based on considered characteristic tension resistance, the nail solution provides 8.0 kN per fastening point while the screw solution provides 3.99 kN per fastening point

As a result, fewer fastening points are required with the nail solution to resist the same uplift demand. In this specific example, the number of required fastening points using nails is half of the number required when using screws.

This shows that, for this specific load case, higher fastener resistance can enable an optimised fastening layout with fewer connection points. For specifiers, this highlights the importance of considering fastener performance during the design phase. For contractors, fewer fastening points can support a simpler installation sequence and reduce repetitive fastening operations on site. Final fastening layouts must always be verified by the responsible designer or engineer according to the applicable approvals, project conditions, and design requirements.

Total Installation Time

Finally, following the value engineering analysis, the total installation time was assessed in detail to understand how the fastening solution can influence the overall jobsite workflow.

Installation time is an important factor when comparing fastening solutions for roof metal deck applications. In large roof areas, productivity is influenced not only by the speed of each fastening point, but also by the full installation workflow.

For this comparison, the installation workflow was considered in the following steps:

• (1) Prework

  — Install of safety net, checks and scaffolding

• (2) Open & Close

  — Pulling and storing equipment and consumables

• (3) Prep

  — lifting, layout, marking, and tacking if applicable

• (4) Frame fastening

• (5) Side lap fastening

• (6) Cleanup of metal chips

For frame fastening, the reference installation time considered is 6 seconds per X-ENP-19 nail compared with 24 seconds per single framing screw. This means that, under the assessed conditions, the nail solution is approximately 4 times faster per frame fastening point. For side lap fastening, the collated nail solution is considered approximately 2 times faster than single sidelap screws.

As a result, the fastening phase is reduced from approximately 6.9 days with single screws to approximately 1.5 days with the nail and collated nail solution. When the complete installation workflow is considered, including preparation and cleanup, the total installation time is reduced from approximately 12.5 days to approximately 6.5 days. This corresponds to a reduction of about 48% in total installation time under the assessed project conditions – see Figure 6.

Figure 6 – Total installation time in days – Nail solution vs screw solution

This productivity improvement is also supported by the installation method. Single screw installation typically involves repeated bend-down and stand-up movements, while nail-based frame fastening and collated side lap fastening can be carried out with stand-up tools. This can support a more ergonomic and consistent installation process over large roof areas – see Figure 7.

Figure 7 – Single screw bending down (left) and nail fastening with stand-up tools (right)

Cleanup can also influence the total time. Self-drilling screws can generate metal chips during installation, which may require additional cleaning before handover or before the next trade can continue. In comparison, powder-actuated frame fastening does not create the same drilling-related chip generation.

Overall, the installation time advantage comes from the combination of faster frame fastening, faster sidelap fastening, stand-up installation, and reduced cleanup effort. For contractors, this can support faster execution and improved ergonomics on site. For specifiers, it shows that the fastening solution can influence not only structural performance, but also constructability and jobsite efficiency.

Conclusion

The comparison between screw and nail technologies for roof metal deck fixing reveals that both solutions offer robust performance across a range of technical criteria, including base material compatibility, load resistance, approvals, fatigue, and seismic suitability. Screws demonstrate greater versatility for thinner base materials and superior corrosion resistance, making them the preferred choice for uninsulated roofs exposed to outdoor environments. Nails, on the other hand, excel in applications involving thicker base materials and provide higher tension resistance, which is particularly advantageous when uplift wind loads are the primary design consideration.

Beyond the technical comparison, the value engineering and installation time assessment show that fastening performance can also influence the overall efficiency of the application. In the specific load case considered, the higher resistance of the nail solution enables an optimised fastening layout with fewer connection points compared with screws. Combined with faster frame fastening, stand-up installation, collated side lap fastening, and reduced cleanup effort, this resulted in an installation time reduction of approximately 48% in the assessed example. For specifiers, this highlights the importance of considering fastening technology not only from a structural perspective, but also in terms of constructability and execution. For contractors, it shows how the right fastening solution can help simplify the installation sequence and improve productivity on large roof deck applications.

Ultimately, the optimal choice between screws and nails depends on the specific requirements of the roofing application, environmental exposure, and project priorities. For fixing in thinner base materials (like purlins), screws might be more versatile and therefore the recommended technology. For applications where installation speed and cost savings are critical, particularly in insulated or dry indoor settings in thicker base materials, nails present a compelling solution.

References

[1] European Organisation for Technical Assessment (EOTA). (2025). What is an ETA? Retrieved December 3, 2025, from https://www.eota.eu/about-eta

[2] Beck, H., Siemers, M., Reuter, M., & Schöffendt, E. (2019). Setzbolzen und Metallbauschrauben. In U. Kuhlmann (Ed.), StahlbauKalender 2019: Verbindungen, Digitales Planen und Bauen (Ch. 8). Berlin, Germany: Ernst & Sohn.

[3] European Committee for Standardization (CEN). (2005–2007). Eurocode 3: Design of Steel Structures (EN 1993 series). Brussels, Belgium: CEN.

[4] European Organisation for Technical Assessment (EOTA). (2015). European Assessment Document EAD 330153-000602: Cartridge Fired Pin for Connections of Thin Gauge Steel Members and Sheeting. Brussels, Belgium: EOTA.

[5] Deutsches Institut für Bautechnik (DIBt) & Valtion Teknillinen Tukimuskeskus (VTT). (2007). CUAP – Common Understanding of Assessment Procedure: Fastening Screws for Metal Members and Sheeting. Berlin, Germany / Espoo, Finland: DIBt/VTT.

[6] ICC Evaluation Service (ICC-ES). (2019). AC70: Acceptance Criteria for Fasteners Power-Driven into Concrete, Steel and Masonry Elements. ICC-ES Acceptance Criteria, Brea, CA.

[7] ICC-ES Evaluation Service. (2017). ESR-2776: Steel Deck Diaphragms Attached with Hilti X-HSN 24 or X-ENP-19 L15 Powder-Driven Fasteners and Hilti S-SLC 01 M HWH or S-SLC 02 M HWH Sidelap Connectors, or Verco Decking VSC2 Sidelap Connection. ICC-ES Evaluation Report, Brea, CA. Reissued April 2017, revised December 2017.