Screw Head and Fastener Waterproofing for Metal Roofs

Every screw in a metal roof is a small hole through the sheet, sealed only by a washer. A typical warehouse roof has thousands of them, so when washers age or screws rust, leaks break out in many places at once. ETCE replaces failed fasteners with larger stainless steel screws and caps the heads with Promax Bonding Adhesive to stop both the leaks and future rust.

Across Saudi ArabiaUp to 15-year warrantyFree roof survey

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B&R Gulf – Dammam

Why fasteners fail in the Saudi climate

The rubber washer under each screw head is the only thing keeping water out of the hole. On a roof that reaches very high surface temperatures every summer afternoon, that washer slowly hardens, shrinks and cracks. Meanwhile the sheet expands and contracts around the screw each day, working it loose until it backs out and lifts the washer off the metal. On the coast at Dammam, Al Khobar and Jubail, salty humid air adds rust, which eats the screw head and widens the hole.

Simply tightening old screws rarely helps, because the thread has often stripped the hole or rusted through. Instead, we replace every rusted, torn-out or backed-out screw with a stainless steel screw one size larger, so it grips fresh metal, fitted with a new EPDM washer. Each head is then covered with Promax Bonding Adhesive, which seals it from moisture and holds it firm against the loosening effect of thermal movement.

Signs your roof screws are failing

Orange rust rings around screw heads on the roof surface
Screws standing proud of the sheet, or missing altogether
Small drips in straight rows that follow the purlin lines
Cracked, flattened or perished washers
Rust spots on the underside of sheets at fixing points

How we treat roof screws

Fastener surveyOur engineer checks fixing lines across the roof and photographs rusted, loose, torn-out and missing screws.
Remove failed screwsScrews that are rusted, torn out or backing out are taken out, leaving the purlin connection ready for a new fixing.
Fit one size largerEach is replaced with a stainless steel screw one size up with a new EPDM washer, so it bites into sound metal.
Clean the headsAll screw heads in the treated area are cleaned of dust and loose rust so the adhesive bonds fully.
Cap with adhesivePromax Bonding Adhesive is applied over each head and washer until it is completely enclosed.

Materials & workmanship

Stainless steel replacement screws, one size larger than the originals
A new EPDM washer on every replacement screw
Promax Bonding Adhesive caps over each screw head, rated to 120 °C
Work carried out from the roof on lifelines while the building stays open

Photos from ETCE projects

Screw Heads & Fasteners - B&R Gulf, Dammam

Screw Heads & Fasteners - Zamil Group Real Estate, Al Khobar

Screw Heads & Fasteners - Aqua Cool Saudi Arabia Co. Ltd., Dammam

Screw Heads & Fasteners - Saudi Arabian Industrial & Trading Co. Ltd., Dammam

Site photos from ETCE projects in Saudi Arabia and Bahrain. Tap to enlarge.

Frequently asked questions

Why do you use a screw one size larger?

When a screw has rusted or pulled out, the original hole is usually enlarged or its thread is damaged. A slightly bigger screw cuts a fresh grip into sound metal, so it stays tight instead of spinning in the old hole.

Do you cap every screw or only the damaged ones?

Damaged screws are replaced, and capping normally covers the full fixing lines being treated, so sound screws are protected before their washers fail as well. The survey report sets out the scope, and nothing starts until you approve it.

Why stainless steel?

Ordinary carbon steel screws rust quickly in the humid, salty air of the Eastern Province. Stainless steel resists that corrosion, and once the head is capped with adhesive, moisture cannot reach it at all.

Can our maintenance team just go round with a tube of silicone?

Sealing over a rusted or loose screw traps the problem underneath, and the leak usually returns the next time the screw moves. Walking a roof near skylights without lifelines is also a genuine fall risk, so this work is best left to a trained crew.