STAINLESS STEEL POZI RAISED COUNTERSUNK WOODSCREWS 15MM SEALING WASHER

Pozi Raised Countersunk Woodscrews 15mm Sealing Washer — Fixing exterior timber boards — fascia, soffit, cladding, roofing trim — creates one specific problem ordinary woodscrews don't solve: water tracking down the screw shank into the clearance hole and into the timber or substrate beneath. This screw solves it with a bonded washer, typically rubber or EPDM, fitted under a raised countersunk head; as the screw is driven, the washer compresses against the board surface and closes the gap around the hole. At 15mm diameter it's the smallest of the three sealing washer sizes offered, which suits thinner boards, smaller clearance holes, or fixings where a lower-profile, less visible washer is wanted over the broader coverage of the 20mm or 25mm options. The head itself follows the raised countersunk pattern (the same base shape as DIN 7995), giving a slightly domed, part-proud finish once seated, and is driven with a Pozidriv recess — a practical middle ground that resists cam-out considerably better than a slotted screw without the added cost of hexalobular, which matters most for repeated power-tool or impact-driver use rather than the occasional fascia board. Because this fixing sits outdoors and often at height, in gutters, or on exterior cladding, stainless steel is the sensible baseline rather than an option: A2 (304-equivalent) copes well with typical UK rainfall and general external exposure. A4 (316-equivalent) is worth specifying for coastal properties, buildings near swimming pools, or cladding subject to road salt spray, where the extra molybdenum resists chloride pitting that A2 can eventually develop in those harsher settings. Choosing the right washer size comes down to board thickness and clearance hole diameter — bigger holes or thicker, more compressible board materials need more sealing surface, which is exactly what the 20mm and 25mm versions in this range provide, while gauge and length should still be sized to give solid thread engagement in the substrate beneath.

FAQs
When should I choose the 15mm washer instead of 20mm or 25mm?
Choose 15mm for thinner boards, smaller clearance holes, or where a less visually prominent washer is wanted; move up to 20mm or 25mm where the hole is larger or the board is thicker and needs a wider sealing footprint.

Does the sealing washer replace the need for any other weatherproofing?
No — it seals the immediate gap around the screw hole, but overall weathertightness of a cladding or fascia system still depends on correct board overlap, flashing, and general detailing; the washer addresses just the fixing point.

Can this screw be used indoors as well?
It can, but the sealing washer serves no purpose indoors, so a standard raised countersunk woodscrew without a washer is the more cost-effective choice for interior fixing.

Should I choose Pozi or hexalobular for this washer size?
Pozidriv suits occasional or hand-driven fixing well; hexalobular is the better choice for high-volume or impact-driver installation, such as fitting a full cladding run, since it resists cam-out more consistently under sustained torque.