When repairing or restoring metal roofing, it is important that you choose waterproofing products carefully to ensure your efforts yield long-lasting results. While there are a variety of roofing tapes and sealants developed specifically for metal roofing repair applications, different end-use environmental and substrate conditions factor into which chemistry or product construction is best for a job. If you take a methodical approach to product selection, you can avoid frustration later.
The correct waterproofing products ensure long-lasting results
Start with the Surface
Begin by inspecting the specific substrate you will be sealing. Whether it’s coated, painted or bare metal, these factors can affect what sealing products will adhere to the surface. Remember that you need a tape or sealant that will bond to any coating, not just the underlying metal. You may not always know what existing coatings are in play when making repairs, so to be safe, use an adhesive product that can bond to even the most challenging coatings, such as Kynar 500 PVDF, a high-performance paint often used on metal roofing that poses problems for many adhesives. Keep in mind that you must clean the surface of contamination prior to tape or sealant application for the best bonding to any roofing substrate.
Denatured alcohol, acetone and lacquer thinner are typically used for cleaning; we generally recommend them in that order. Avoid soap, as adhesive bonds can be jeopardized if they are formed with a soap’s film layer rather than the roofing substrate. Also, check the roofing substrate manufacturer’s recommendations for any additional surface preparation considerations.
Compare your Options
Based on the surface you are sealing, determine whether you need tape, tubular sealant or both. Roofing tape is useful for stopping leaks in areas like seams or fastener penetrations and can help ensure a roof is watertight prior to application of a new roofing coating. Pressureapplied MicroSealant tapes, such as Schoolcraft, Mich.-based Chem Link Inc.’s WebSeal Roof Repair Tape, feature non-butyl synthetic rubbers and resins or thermoplastics that form an instant, primer-like, tenacious bond at the molecular level to most known materials used in traditional roofing applications, with the exception of silicone. These highly conformable products are capable of self healing after fusing to a substrate, making them an ideal solution for sealing leaks on finished or coated metal roofs as long as there is less than 40 percent rust on the surface.
The other option to consider is a durable, neutral-cure, solvent-free, low-modulus silicone sealant like Chem Link’s MetaLink High-Performance Metal Roof Sealant. It is designed to stick to paint and coatings as difficult as Kynar 500 PVDF without shrinking or promoting metal corrosion during curing. These highly elastic sealants are good for sealing along edges, atop fasteners or on seams, and they can flex substantially without pulling away from surfaces. A low-modulus silicone sealant that has 50 percent movement allowance that is used to fill a 1-inch gap, for example, will maintain its bond even when the gap fluctuates between 1/2 inch and 1 1/2 inches.
Don’t Forget Penetrations
Be sure penetrations in the roof, such as points where pipes emerge, are properly sealed as well. Neoprene boots traditionally used to seal around penetrations are often destroyed by UV rays over time, and repairs may be necessary. A system like Chem Link’s E-Curb Metal Roof Penetration Seal can cut repair times down to around 15 minutes by relying on precast components and requiring no flashing or mechanical attachments. Precast systems like E-Curb can be modified to fit over ribs in metal roofing or agricultural paneling that typically has rounded ribs every 8 to 9 inches, ensuring a strong seal.
On a pitched metal roof, we recommend using a non-slump elastomeric sealant like Chem Link’s DuraLink 50 to fill the precast components and to seal them to the roofing substrate, as it sticks to even Kynar 500 PVDF coatings and is viscous enough that it won’t run out the side of the precast form component like a self-leveling, one-part polyether pourable sealant might.
Make the Most of Your Time
No matter what sealing products you choose, keep in mind that tapes and sealants can be applied down to near-freezing temperatures, so you don’t have to wait for warm weather to get a repair job started. You can do all your prep work, then wait for warmer weather to apply coatings, making the most of your labor force availability. By choosing the right products, you can be sure you receive not only strong long-term metal roofing performance, but a quicker, more convenient repair job, too.
Dan Belisario is northeast region district manager for Chem Link Inc., Schoolcraft, Mich. To learn more, visit www.chemlink.com
