Structural full-thread wood screws
for timber connections and reinforcement
Structural connections, beam reinforcement, and protection against cracking in solid and engineered wood
High-resistance self-tapping screws with thread running the full length of the shank, for maximum withdrawal resistance. Designed for load-bearing timber structures — from solid wood to CLT, LVL and glued laminated timber. Available in cylindrical head (also known as pan head) and countersunk head configurations.
Ø6 · Ø8 · Ø10 mm TORX No predrilling required Wax-coated CE-marked ETA-18-0817 Solid Wood · CLT · LVL · Glulam
Product variants
Cylindrical head vs countersunk - choosing the right type of head
Cylindrical head
Also known as cheese head · Torx TX drive
The cylindrical head (cheese head) has a narrow profile that easily sinks into wood. Its compact geometry makes it the ideal choice for installation at an angle — screwing at 45° in inclined reinforcement connections — where a countersunk conical head would get stuck against the face of the wood.
Recommended applications:
- Structural reinforcement at an angle
- Wood-to-wood connections
- Beam coupling and connections where the screw is insertedee in Store at an angle relative to the wood surface
Countersunk head
Flat head · Torx TX drive
The countersunk head uses a conical angle that sits and sinks into the face of the wood. It performs best when inserted perpendicular to the surface, where the cone fits cleanly into the fiber. The right choice when overlapping materials — panels, sheets, or coverings — need to lie completely flat.
Practical advantage:
- Joining wooden structures
- Reinforcing wooden structures
- Protecting structures against cracking
Main technical features
Why full thread is essential in structural connections
Full thread — no separation effect
The thread along the entire shaft keeps the two elements in continuous contact, preventing them from separating under cyclic loads or vibration.
High starting resistance
The thread profile distributes shear stresses over a significantly larger contact area than nails or partial thread screws, resulting in higher pull-out values.
Self-drilling tip with cutting notches
The integrated notches cut the wood fibers during insertion instead of crushing them, reducing the risk of splitting and eliminating the need for pre-drilling in most substrates.
Wax coating reduces tightening torque by up to 20%.
Applied in production, the lubricating coating decreases insertion resistance, extending the life of batteries and screwdriver bits.
High-strength steel
Yield strength (fy,k) up to 1000 N/mm² — a value significantly higher than that of conventional construction screws and wood expansion screws.
Load in any direction relative to the grain
Approved for structural applications with loads at any angle relative to the wood grain (α = 0° to 90°), ideal for complex connections.
Compatible with engineered wood
Tested and certified for solid wood, CLT, LVL, KVH, BSH (glued laminated timber), and OSB panels.
Reduced minimum spacing
The full thread geometry allows for more compact groupings compared to traditional fasteners, optimizing sizing in connections with restricted space.
Ø6 / Ø8 / Ø10mm
Available diameters
Torx -TX
Drive
up to 1000 N/mm²
Steel strength
Pre-drilling - Not required
Recommended pre-drilling for Ø10 mm screws in high-density hardwoods (above 600 kg/m³) and in negative temperature conditions, to avoid splitting.
100% full thread
Thread coverage
Zinco + cera
Coating
Applications
Where full thread structural screws are used
Wood-to-wood connections
Joining beams in overlap or end-to-end; the full thread locks both elements without separation.
Structural reinforcement
Reinforcement of cracked or weakened beams; screws work in tension perpendicular to the grain
CLT and solid engineered wood
Panel-to-panel connections, wall-to-floor joints, and shear reinforcement in CLT assemblies
Rehabilitation and retrofit
Reinforcement of existing structures without the need for resins or wet processes
Glued laminated timber and LVL
Tested and approved for KVH, BSH, GLT, and LVL with certified pull-out values.
Roof structures
Connections of rafters, fastening of battens and brackets, and beam-to-joist connections
Seismic and wind resistance
High pull-out resistance withstands lifting forces; inclined insertion improves lateral performance
Full thread structural screws are approved for both new construction and rehabilitation — including connections in load-bearing structures made of CLT, LVL, KVH, and BSH (glued laminated timber).
Market overview
Comparison of the main full thread structural screws
| Feature | Klimas WKFC/WKFS | Traditional screws |
|---|---|---|
| Thread coverage | ✓ 100% full thread | ✗ Partial thread |
| Self-drilling tip | ✓ Self-drilling - With cutting notches | ✗ Requires pre-drilling |
| Steel strength | up to 1000 N/mm² | ~400–600 N/mm² |
| ETA approval / CE marking | ✓ CE marking - ETA-18-0817 | ✓ EN 14592 |
| Certified for CLT/LVL | ✓ Tested and certified | Limited data |
| Torque reduction (wax) | ✓ up to 20% | ✗ |
| Load in any direction to the grain | ✓ α = 0°–90° | ✗ Only axial |
| Available head types | Cylindrical / Countersunk | Hexagonal only |
| Reversible installation | ✓ Can be removed | ✓ |
Best practices for structural installation
Installation guide
1️⃣ Before you start
- Identify the species and density of the wood. Pre-drilling is recommended for screws Ø10 mm in hardwoods with a density above 600 kg/m³ and in cold weather below 0°C.
- Select the correct length: the length of the thread embedded in the receiving element must correspond to at least 4× the diameter of the screw to ensure adequate pull-out resistance.
- Check the moisture content of the wood. Avoid applying to green wood with a moisture content above 20% whenever possible; for outdoor use, prefer stainless steel versions or those with a C4 coating.
2️⃣ During installation
- Use a screwdriver with torque control set to the appropriate value — over-tightening long fully threaded screws reduces pull-out resistance and can cause breakage due to twisting.
- Screw in long screws in a single continuous motion, without interruptions. Stopping halfway causes friction buildup and the risk of seizing.
- For screws inserted at 45° (oblique position), both pull-out resistance and lateral performance are improved — a common technique in beam-to-beam and beam-to-post connections.
✔ Easier correction
Unlike nails, structural screws can be completely removed and reinstalled without compromising the wood element. A decisive advantage in prefabricated structures and phased assemblies.
FAQ
Here are some answered questions about screws for structural connections and beam reinforcement.
The fully threaded screw has threads along the entire shaft, ensuring that both connected elements are in contact with the thread. This eliminates the separation effect of partial thread screws, where the unthreaded area can allow the elements to move apart under load.
The full thread is preferred whenever simultaneous pull-out and compression resistance between the elements is desired.
Both heads sit level with or below the surface of the wood — the structural performance is identical as the entire load is transmitted through the full thread.
The cylindrical head is more suitable for situations where angled reinforcement is needed. When the screw is driven into the wood at an angle, the cylindrical head sinks better into the wood, providing a better finish.
In most cases, no. The self-drilling tip with cutting notches allows for direct installation in softwoods and most engineered woods.
Pre-drilling is recommended for screws Ø10 mm in high-density hardwoods (above 600 kg/m³), at negative temperatures or on edges and ends of pieces where the risk of splitting is greater.
Yes. The fully threaded structural screws are tested and certified for CLT, LVL, KVH, BSH (glued laminated timber), and other engineered wood products.
Always consult the specific product ETA documentation for sizing values in these substrates.
The Torx drive transmits torque more efficiently with a lower risk of tip slippage than Pozidriv or Phillips. In structural screws installed with a screwdriver, the TORX ensures precise torque control and eliminates the risk of damaging the head due to tip slippage — a critical aspect in work at height or in hard-to-access areas.
Solid wood (softwood and hardwood), glued laminated timber (GLT/BSH), KVH, cross-laminated timber (CLT), LVL and wood-based panels including OSB, plywood, particleboard, MDF, and cement-bonded wood panels.
Yes — unlike nails or staples, screws can be reversed and removed with the same TORX driver. Corrections, adjustments and disassembly are straightforward without damaging the wood element, which represents a significant advantage in prefabricated construction and phased assemblies.
✽ Standards and certifications
Regulatory compliance
CE marking / EN 14592
Structural screws for load-bearing connections in Europe must be CE marked under EN 14592 or an ETA. This requirement confirms that the mechanical resistance has been tested and certified by an independent entity.
ETA (European Technical Assessment)
Documents such as ETA-18/0817 provide tested calculation values for pull-out, shear, and combined loads on specific substrates — including CLT, LVL, and glued laminated timber. Always check the annex of the ETA for the product you are sizing.
Eurocode 5 (EN 1995-1-1)
The design of wood connections with structural screws follows EC5, which requires verification of the mechanical compatibility between the fastener and substrate, including resistance to pull-out and transverse forces under combined loads.
✽ Advantages compared
Structural screws vs. traditional fasteners
Traditional nails and expansion screws
- Wood expansion screws require two-step pre-drilling; nails are permanent
- Inferior steel quality (typically 400–600 N/mm²) limits certified load capacity
- Partial thread can create a separation effect of the elements under cyclic loads
- Conservative pull-out values in EC5 due to unverified tensile strength
Full-thread structural screws
- Self-tapping — direct installation with a single tool, no pre-drilling in most applications
- High-strength steel (up to 1000 N/mm²) allows for higher certified calculation values
- Full thread prevents separation of elements and maintains connection integrity under movement
- Reversible — can be removed and reinstalled without damaging the wood, ideal for phased construction
When structural connections are important
Solution for reinforcing and structurally connecting beams in any direction, at an angle or straight.
