The ULAMEX Torx Wood Screw is a high-performance fastener manufactured from A2 stainless steel (1.4301 / AISI 304), designed for securing photovoltaic roof hooks and mounting brackets directly into timber rafters and purlins. The large flat head (Tellerkopf) distributes the clamping force over a wide bearing area, preventing the screw head from pulling through the roof hook base plate — a critical safety requirement in wind-loaded PV rooftop installations.
Technical Specifications
| Parameter | Value |
|---|---|
| Material | A2 stainless steel (1.4301 / AISI 304) |
| Drive | TORX (star drive) — T30 (Ø6) / T40 (Ø8) |
| Head type | Large flat head (Tellerkopf) |
| Thread | Coarse wood thread, partial thread |
| Ø6 sizes | 6×60 / 6×80 / 6×100 mm |
| Ø8 sizes | 8×60 / 8×80 / 8×100 / 8×120 mm |
| Head diameter | ~15 mm (Ø6) / ~20 mm (Ø8) |
| Material thickness penetration | Min. 40 mm thread engagement in rafter |
Installation Guidelines
Position the roof hook or mounting bracket on the timber rafter at the marked location. Pre-drill a pilot hole with a diameter of 4 mm for Ø6 screws or 5.5 mm for Ø8 screws to a depth slightly exceeding the screw length. Pre-drilling is recommended for A2 stainless wood screws to reduce driving torque and prevent thread galling in dense hardwoods.
Drive the Torx wood screw using a power drill or impact driver fitted with the correct bit — T30 for Ø6, T40 for Ø8. The TORX star drive provides superior torque transfer compared to Phillips or Pozidriv systems, virtually eliminating cam-out (bit slipping) even at high driving torques. Set the driver clutch to prevent over-driving — the screw head should sit firmly against the hook base plate without crushing the wood fibres beneath.
For roof hook installations, a minimum of two screws per hook is standard, using the pre-drilled holes in the hook base plate. Select the screw length to achieve at least 40 mm of thread engagement in the rafter after subtracting the base plate thickness and any tile-adjustment washer stack. For rafters less than 60 mm wide, use Ø6 screws to reduce splitting risk.
Applications
- Roof hook fastening — primary attachment of PV roof hooks to timber rafters through tile battens for pitched-roof solar installations
- Mounting bracket connections — securing angle brackets and adjustable tilting brackets to purlins and sub-rafters
- Tile-roof PV systems — hook base plate to rafter connections where the screw must pass through the roof hook and into solid timber
- Timber substructure reinforcement — additional fixings for doubled or sistered rafters carrying concentrated PV loads
- Solar thermal panel mounting — equivalent fastening requirements for solar thermal collector brackets on timber roofs
Material Properties
A2 stainless steel (1.4301 / AISI 304) provides the corrosion resistance required for fasteners embedded in timber roof structures where moisture exposure is inevitable. Unlike galvanised screws, which can lose their zinc coating over time through abrasion during thermal cycling, the stainless passive oxide layer is integral to the alloy and self-regenerating. This ensures consistent pull-out strength over the 25+ year service life expected from PV installations.
The coarse wood thread is optimised for high pull-out resistance in softwood species commonly used in European roof construction (spruce, pine, larch). The partial-thread design ensures that clamping force is generated between the screw head and the rafter surface, not within the threaded zone — preventing the hook base plate from lifting off the rafter surface.
Compatibility
The ULAMEX Torx wood screw is the designated fastener for:
- ULAMEX roof hooks — all adjustable and fixed roof hook models with standard base plate bore patterns
- PV mounting rails 40×40 and 80×40 — indirectly, via the roof hook substructure
- Mounting brackets and angle adapters — timber-mounted structural connection points
- EPDM washers — for sealing the roof penetration point at the hook base plate
Why ULAMEX
ULAMEX is an EN 1090 certified B2B wholesaler supplying the complete PV roof mounting system — roof hooks, profiles, clamps, and all fasteners. All seven Torx wood screw sizes are stocked for immediate dispatch in bulk packaging (100, 250, 500 pcs) with pallet delivery across Europe.
Frequently Asked Questions
Q: Do I need to pre-drill for stainless steel wood screws?
Yes. Pre-drilling is strongly recommended for A2 stainless wood screws. Stainless steel is harder than standard carbon steel, generating higher driving torque that can cause thread galling or screw breakage in dense wood without a pilot hole. Use a 4 mm bit for Ø6 and 5.5 mm bit for Ø8 screws.
Q: Why TORX drive instead of Phillips or hex?
The TORX star drive provides superior torque transfer with virtually zero cam-out (bit slipping). This is critical for long wood screws driven into dense rafters where high torque is required. The positive engagement also reduces bit wear and screw head damage, ensuring reliable reusability during hook repositioning.
Q: What screw size for my roof hooks?
Select based on rafter thickness and hook base plate bore: Ø6×80 is suitable for standard 60-80 mm rafters. Ø8×100 or Ø8×120 for heavy-duty applications or thicker rafter sections. Ensure minimum 40 mm thread engagement in the rafter.
Q: How many screws per roof hook?
Standard practice is 2–4 screws per hook, depending on the hook model and the expected wind uplift load. Follow the mounting system manufacturer’s installation guide. Most ULAMEX roof hooks have 2 or 4 pre-drilled base plate holes.
Need Torx wood screws for your PV roof installation? Request a Quote | +48 504 424 761 | [email protected]