PZ Countersunk Wood Screws (EWI to OSB) are hardened, yellow-zinc coated timber screws designed for secure fixing into timber and wood-based sheathing boards such as OSB, plywood, MDF and chipboard. Featuring a PZ countersunk head for a flush finish and a partial thread for excellent pull-down strength, these screws are ideal for timber construction and for fixing insulation support discs when installing EWI systems onto OSB substrates.

Engineered from hardened carbon steel with a durable anti-corrosion coating, these screws deliver secure, long-lasting performance in both structural timber and sheathing applications. Their sharp cutting thread ensures fast bite and reduced drive torque for efficient installation on site.

Suitable Applications

Key Features

• PZ countersunk head for a clean, flush finish.
• Hardened carbon steel with yellow zinc coating for corrosion resistance.
• Partial thread ensures strong pull-down clamping action.
• Fast-starting thread for reduced installation torque and faster work onsite.
• Ideal for timber structures and OSB sheathing.
• Proven for use with insulation support discs in EWI on timber.

Compatible Substrates

Sizes & Box Quantities

Application

Preparation

• Confirm substrate is timber-based.
• Pair with insulation discs when fixing EWI boards to OSB.
• Pre-drill in dense hardwood to avoid splitting.

Installation Steps

• Position screw (and disc if used).
• Drive with a suitable PZ bit until head sits flush.
• Ensure insulation or timber component is pulled tight.

Quality Checks

• Check screws sit fully flush.
• Ensure strong grip, no free-spinning.
• Replace any fasteners with damaged heads or threads.

For EWI applications on timber substrates, pair with our Universal Fixing Discs for enhanced load distribution and secure insulation fixing.