How to Properly Seal Seams in Metal Roofing
When it comes to standing seam metal roofing, your roof is only as strong as its seams. A high-quality metal panel can last decades, but if the seams aren’t sealed right? You’ve got a leak waiting to happen.
At L&L Roofing & Construction, we help homeowners across Gainesville and surrounding towns get the most out of their metal roofs — and that starts with proper seam sealing.
Why Seam Sealing Matters
Seams are the joints where one panel meets the next. Without a reliable seal:
- Water intrusion can cause hidden leaks.
- Thermal movement may break weak seals.
- Mold, rust, or structural damage may follow.
Whether you’re installing a new standing seam metal roof or repairing an older one, sealing those joints correctly is non-negotiable.
Best Practices for Sealing Metal Roof Seams
Here’s what we use and recommend for sealing standing seam and lap seams on metal roofing systems:
✅ Use Butyl Tape or Non-Skinning Butyl Sealant
- Butyl tape is ideal for end laps and rib joints. It stays flexible, maintains adhesion over time, and doesn’t dry out.
- Non-curing butyl tubes are used where a tape can’t reach — like complex corners or trim overlaps.
- Always apply sealant to a clean, dry surface for proper bonding.
✅ Internal Seal First, Not Surface Caulk
Avoid relying on caulking the outside of seams. It may look sealed but will degrade in sunlight. Instead:
- Apply sealant between panels, not on top.
- Rely on internal compression of sealant between layers for a watertight seal.
✅ “Marry” Your Sealant Beads
In critical intersections — like where a panel meets a gutter or ridge cap — we always blend intersecting beads of sealant into a continuous, unbroken seal. We call this a “pigtail” connection.
✅ Don’t Overdo It
Too much sealant can cause bulging at clips or panels and may even block drainage. Stick to manufacturer specs for bead size and application method.
✅ Plan for Thermal Movement
Metal expands and contracts. That movement will tear a brittle seal. That’s why we:
- Use sliding clips in concealed fastener systems.
- Place sealant in locations that allow panel movement without stress.
Common Mistakes to Avoid
- Using the wrong sealant: Silicone often doesn’t bond well with metal and may not be compatible with existing coatings.
- Exposed caulking: This will crack, peel, or wash away over time.
- Skipping seam checks at ridges and eaves: These spots take the brunt of rain and wind and are often the first to fail.
When to Call in the Pros
Some sealing can be DIY, but full seam resealing or diagnosing leaks at joints should be left to a qualified roofing contractor. Especially with standing seam systems — one wrong step can void warranties or create more problems than it solves.
At L&L Roofing & Construction, we use manufacturer-approved sealants, precision techniques, and over a decade of metal roofing experience to ensure your seams stay sealed tight.
FAQ: Seam Sealing for Metal Roofs
How long does seam sealant last on a metal roof?
With proper installation, butyl-based sealants can last 25–60 years — often as long as the roof itself.
Can I use silicone to seal my metal roof seams?
Usually not. Unless it’s a neutral-cure silicone rated for metal roofing, it may damage your panels or not adhere properly.
Is seam sealing required for all standing seam roofs?
Not always. Some systems are designed with interlocking seams that don’t require sealant. But for extra weather protection, we often apply internal sealants where appropriate.
Need help with a metal roof in Gainesville, Cumming, or Buford? We’d be honored to take a look.
Call us at (770) 874-0372 or schedule your free inspection today.