What to Put Under Metal Roofing: A Comprehensive Guide: 1 Minute to Understanding Your Metal Roofing OptionsSarah ThompsonSep 09, 2025Table of ContentsTips 1:FAQTable of ContentsTips 1FAQFree Smart Home PlannerAI-Powered smart home design software 2025Home Design for FreeWhen installing metal roofing, what you place underneath—known as underlayment—is just as critical as the roofing itself. Choosing the right underlayment prolongs your roof’s lifespan, enhances weather protection, and supports proper insulation. The main options include felt, synthetic underlayment, and self-adhering membranes. Felt underlayment (usually asphalt-saturated) has been a traditional choice. However, synthetic options are now popular due to their superior tear resistance, lighter weight, and greater resistance to moisture. In regions prone to ice dams or heavy storms, self-adhered membranes offer an extra barrier against water intrusion.Another crucial layer is the roofing deck, which serves as the base for underlayment. Most metal roofs are installed over plywood or OSB (oriented strand board). Sometimes, an additional vapor barrier is recommended, particularly in humid or cold climates, to prevent condensation beneath the metal panels. Depending on your local building codes, climate, and the roof’s pitch, the optimal underlayment system may vary.As an interior designer, I always look for effective solutions to bridge function and aesthetics in home projects. The same philosophy applies to what’s under your roof. The right combination of materials not only ensures protection but also supports a well-thought-out home environment. If you’re in the process of renovating or planning a new build and want to visualize how roofing choices interact with interior comfort, tools like a 3D floor planner can help you explore and plan structural layers, making sure the interior remains just as pleasing and high-performing as the exterior.Tips 1:Always check local building codes before finalizing your underlayment choice, as certain areas require specific materials to meet safety standards.FAQQ: What is the best underlayment for metal roofing?A: Synthetic underlayment is highly recommended for most metal roofing due to its durability, moisture resistance, and ease of installation. However, climate, roof pitch, and local codes may influence your final choice.Q: Can you put metal roofing directly on plywood?A: While technically possible, this isn’t advisable. Always use a suitable underlayment between the plywood roof deck and metal panels to prevent water damage and enhance durability.Q: Is felt paper still used under metal roofs?A: Yes, asphalt-saturated felt is still used, but it’s less popular than newer synthetic options, which offer better performance and longevity.Q: Do I need a vapor barrier under my metal roof?A: In certain climates—especially humid or cold areas—adding a vapor barrier can prevent moisture buildup and condensation problems beneath the roof.Q: Should insulation go under the metal roofing?A: Roof insulation is often placed beneath the roof deck. Proper insulation, in combination with quality underlayment, increases energy efficiency and interior comfort.Home Design for FreePlease check with customer service before testing new feature.