Construction & Roofing Screws

Corrosion decides the service life

Construction fasteners fail for one reason above all others: the finish was specified for the wrong environment. A screw that performs indefinitely inside a dry building envelope will bleed rust stains down a cladding panel within a single winter if it is exposed to coastal air. Because replacing a failed roofing fixing means access equipment and labour, the fastener is almost never the expensive part of the failure.

Getting this right means matching the coating to the actual exposure rather than to the building type.

Finish selection by exposure

Salt-spray figures are indicative neutral salt spray to ISO 9227 and vary with coating thickness and part geometry. Full comparison in the finishes guide.

Why zinc-flake coatings dominate exterior construction

Conventional electroplated zinc protects sacrificially: the zinc corrodes preferentially and the steel survives until the zinc is consumed. That works well but the timeline is short in aggressive conditions, and the plating process introduces atomic hydrogen into hardened steel, which can cause delayed brittle failure in high-strength fixings.

Dacromet and Geo-met are zinc and aluminium flake dispersions applied and cured thermally rather than deposited electrolytically. Two consequences matter on site. First, they deliver several times the salt-spray life of conventional plating. Second, because there is no electrolysis, no hydrogen enters the steel, so the embrittlement mechanism never starts. Ruspert adds a multi-layer system with a ceramic-like top coat for the most aggressive coastal exposure.

Galvanic corrosion: the mistake that ruins good specification

Worth flagging because it defeats an otherwise correct finish choice. When two dissimilar metals sit in contact with moisture present, the less noble metal corrodes preferentially. A plain steel screw driven into an aluminium cladding panel, or into copper flashing, creates exactly this cell, and the resulting corrosion is faster and more concentrated than either metal would suffer alone.

Where you are fixing into aluminium, copper or treated timber, tell us the substrate when you enquire. Treated timber deserves particular attention because modern copper-based preservatives are considerably more aggressive to plain steel than older treatments were.

Products we supply into construction

• Self tapping screws: Ø2.9 to 6.3 mm for sheet, purlin and cladding fixing, in Type A, AB and B thread forms with hex, hex-flange and pan heads.
• Construction and chipboard screws: bugle head with deep coarse thread for timber framing, drywall and sheathing. The bugle profile self-countersinks without tearing the board face.
• Wood screws: Ø3 to 8 mm for structural timber, decking and joinery.
• Custom screws: special lengths, integral washers and non-standard heads made to your drawing.

Heads and drives for site work

Site conditions are the opposite of a controlled assembly line. Fixings go in overhead, in cold, in wet, often one-handed on a ladder, by operators using impact drivers at full speed.

• Hex and hex-flange heads are driven by a socket rather than a recess, so there is nothing to strip and the integral flange spreads load without a separate washer.
• Bugle heads pull flush into timber and board without tearing the surface.
• Torx drives matter more on site than anywhere else. A cammed-out recess on a roof is a fixing that has to be extracted and replaced at height.
• Square drive holds the screw on the bit unsupported, which is genuinely useful for overhead and one-handed fixing.

See the head types chart and the drive types guide for the full range.

Why specify C S Fasteners

We supply builders' merchants, cladding contractors, roofing specialists and construction brands with hardened steel fixings in high-corrosion finishes. Flexible MOQ means you can trial a finish on one project before standardising, and white-label packaging is available for merchants selling under their own brand.

Tell us the substrate, the exposure and the expected service life and we will recommend the finish rather than simply quoting what you asked for. Orders ship export-ready worldwide on FOB or CIF terms with full documentation.