Construction screws
With construction screws the standard matters more than the price. A screw in a load-bearing timber connection must be CE marked to EN 14592 or hold a European Technical Assessment. That ETA supplies the characteristic values the engineer designs with under Eurocode 5. Without that paperwork the screw cannot legally be used in the connection it was calculated for.
Taiwan is strong in exactly this category, and particularly in bi-metal self-drilling screws: a stainless body joined to a hardened carbon steel drill point, which drills through steel while the exposed body stays corrosion resistant. Chinese screws in this group carry an anti-dumping duty of up to 86.5 per cent. Taiwanese ones do not.
Standards and certification
- EN 14592
- Timber fasteners. The harmonised version is 2008+A1:2012, in force since 1 March 2013.
- ETA under EAD 130118-00-0603
- For screws whose performance exceeds the harmonised standard. Supplies the values used in Eurocode 5.
- CPR (EU) 2024/3110
- The new construction products regulation applies from 8 January 2026. CE marking under the old CPR remains valid through the transition.
- DIN 7504
- Self-drilling screw. Point types 1 to 5 determine the maximum steel thickness.
- DIN 7981 / 7982 / 7983
- Self-tapping screws: pan head, countersunk and raised countersunk.
- DIN 18182-2
- Drywall screw for metal stud framing.
- Declaration of Performance (DoP)
- States characteristic load capacity, withdrawal values, yield moment and head pull-through.
- System 3
- The certification route for EN 14592: initial type testing by a notified body plus factory production control.
Types and features
- Countersunk head
- Flush finish, standard in timber and chipboard work.
- Wafer or large flat head
- Wide head for sheet materials, pulls panels down tight.
- Hex washer head
- For self-drilling screws into steel and sandwich panel.
- Partial thread
- The plain shank spins free in the upper member so the joint is drawn together.
- Full thread
- For axially loaded screws and reinforcement applications.
- Torx (TX)
- Transmits high torque with virtually no cam-out, which is why it dominates long construction screws.
- Pozidriv and Phillips
- PZ outperforms PH, but both cam out under high torque.
- Bi-metal
- Austenitic stainless body with hardened steel drill point, for coastal and facade work.
Corrosion and service classes
- Service class 1 (EN 1995)
- Dry, heated interior. Electro-zinc plating is normally sufficient.
- Service class 2
- Covered, occasionally damp. Heavier zinc, zinc flake or A2.
- Service class 3
- Exterior and exposed. A4 stainless or heavy zinc flake.
- Treated timber (ACQ)
- Copper-based preservatives accelerate corrosion of steel and zinc. Specify A4 or a specifically approved coating.
- Wax coating
- Reduces driving torque and heat build-up on long screws.
- EPDM washer
- On roofing screws, for a watertight penetration.
Applications
- Timber frame and prefab: structural screws with ETA, partial thread, in service class 1 or 2.
- Decking: decking screws in A4 for hardwood and coastal locations.
- Roof and facade: self-drilling screws with EPDM washers, bi-metal where chlorides are present.
- Sandwich panels: longer self-drilling screws with point type matched to the steel thickness.
- Interior fit-out: drywall screws to DIN 18182-2, high volume and low unit cost.
- Greenhouse construction: self-drilling screws with raised corrosion protection, given condensation.
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Which screw for which connection
Send your list or your specification. For load-bearing applications I will tell you which ETA or DoP the manufacturer can supply, so your engineer can design with it. Without those documents I will not recommend the screw.