Metal Roofing Update
I admire homeowners who make the choice to invest in metal roofs because of their durability, so be concerned if some installers only offer a one-year guarantee on workmanship. This is at odds with metal roofing’s exceptional material warranties and promise of durability. The Metal Roofing Alliance offers courses for metal roofing installers and contractors to make sure their work stands up to the durability of the metal material, and the test of time. By using proper installation practices your contractor should be offering workmanship guarantees that are more commensurate with a lifetime roofing material. Here are some examples:
Use compatible accessories
An expensive metal roof can be ruined by using cheap or incompatible trim, fasteners, and accessories. Using galvanized materials or fasteners on a galvalume roof, for example, can cause irreparable corrosion and oxidation, compromising the quality of the panels and shortening a metal roof’s life. This is caused by poor planning or laziness because it only costs a small amount more for proper trim, fasteners, and accessories that are compatible with the metal roofing material. The long-term assurance of reduced call-backs… and even better, satisfied customers is well worth the trouble.
Install with water runoff in mind
Use roof flashings and curbs made from aluminum or stainless steel that are most compatible for metal roofs. Galvanized flashing is inferior, won’t last as long and can actually cause corrosion damage. If using galvalume flashing, minimize and check seam welding as this can melt the material’s protective coating.
Use well thought-out flashings and under/over curbs. Make sure you plan for proper clearance in order to give water some room to run off and avoid pooling (a good rule of thumb is a minimum of 12 inches between panel ends and the diverter on the upslope end, and 6 inches between the curb’s sides and panel seams). For big curbs with a heavyweight load, be sure you have proper structural support underneath. Demand use of curbs around chimneys, caulking alone will not hold over time to prevent leaks.
For metal roof plumbing penetrations, do not use standard residential pipe jacks or those made for membrane roofs. Use a pipe boots made to last, from galvalume or aluminum. Move the penetrations to miss panel seams and avoid blocking the flow of water. If other trades need to make penetrations in the roof (like HVAC), be sure they are supervised by the roofer and coordinate the location and method so that only proper techniques and materials designed for metal are used.
Contractors with the proper training should be confident enough in their product to offer workmanship guarantees that make sense. The value of a fine metal roof deserves that.