Repairing vertical seams made simple

By Dani Sheehan. 

Seams may be a weak point on metal roofs, but with the right products, you can deliver durable, watertight repairs. 

Metal roofs are known for their durability and long service life, but like any roofing system, they are not immune to deficiencies. One common problem contractors encounter is open vertical seams. When seams begin to separate, they create pathways for water infiltration, leading to leaks, corrosion, and costly damage to the building below. Fortunately, with the right products and techniques, you can restore watertight integrity and extend the life of the roof. 

In the video below, Chris Huettig, Technical Director of KARNAK, demonstrates a proven repair method using a three-course application with 502MS Karna-Flex Sealant, 799 Wash-N-Prep and 5540 Resat-Mat. 

Why vertical seams fail 

Vertical seams can begin to lift or gap for several reasons: 

• Thermal movement: Metal expands and contracts with temperature changes, stressing seams over time. 
• Improper installation: If panels weren’t aligned or fastened correctly, separation is more likely. 
• Aging materials: Sealants and fasteners can deteriorate, leaving seams vulnerable. 

Left untreated, these deficiencies allow water to bypass the roof’s defenses, leading to leaks that compromise both performance and reputation. 

About the products 

502MS Karna-Flex Sealant

• This single-component, elastomeric thermoplastic-rubber sealant has outstanding adhesion, durability, and flexibility, even at low temperatures. It applies easily by brush or caulking gun and forms a weather-resistant membrane that stands up to the elements. 

799 Wash-N-Prep

• 799 is a concentrated liquid TSP substitute that is designed to clean roof surfaces prior to repair or coating. It improves adhesion without phosphorous, making it both effective and environmentally responsible. 

5540 Resat-Mat

• This stitch-bonded polyester reinforcing fabric has excellent conformability, tensile strength, and tear resistance. It outperforms fiberglass or felts in demanding roof repairs and resists splitting, rot and chemical exposure. 

Together, these products provide you with a reliable repair system to restore performance and extend the life of a metal roof. 

KARNAK makes it simple: clean, seal, reinforce and protect. Watch the video to see just how simple vertical seam repairs can be.