Purlin Replacement and Rusted Purlin Repair for Metal Roofs

Why rusted purlins need attention early

Purlins rarely rust on their own. In most cases water has been coming in from above for a long time, through a failed lap, a loose fastener or a leaking gutter, and settling on the top flange of the purlin where it dries out slowly. On humid coastal sites such as Dammam and Jubail, condensation under the sheets adds to it. By the time flaking is visible from inside, the section may already have lost a good part of its thickness.

A weakened purlin means the sheets above it are no longer held firmly. Fasteners lose their grip, sheets can start to move in strong Shamal winds, and the roof becomes unsafe for anyone walking on it for maintenance. Replacing the corroded section restores proper support, and sealing the leak above protects the new steel so the repair does not have to be repeated a few years later.

Warning signs of purlin corrosion

• Flaking rust or scale on purlins seen from inside the building
• Rust staining running from the roof sheets onto the steel below
• Sheets that sag, shift or rattle between supports
• Fasteners pulling out or spinning without tightening
• Long-standing leaks above the same purlin line

How we replace rusted purlins

1. Inspect from above and belowThe engineer checks the roof sheets and the purlin lines from inside, recording which sections are corroded and how badly in the photo report.
2. Make the area safeAccess is planned so nobody stands on weakened sections, and the crew works with full PPE and safety lifelines.
3. Open up and cut outWhere needed, the sheets over the affected section are lifted in a limited area and the rusted length of purlin is cut out.
4. Fit the new channelA new C or Z channel suited to the site is fixed in place to the original roofing specification.
5. Close and seal the sourceThe sheets are refixed and the original leak, whether at a lap, fastener or gutter, is sealed so water stops reaching the steel.

Materials & workmanship

• C channel and Z channel purlins, chosen to suit the site and the existing structure
• Rusted sections cut out and replaced to the exact roofing specification
• Leak sources above the purlins sealed as part of ETCE's metal-roof rehabilitation

Photos from ETCE projects

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

Frequently asked questions