What Underlayment Is
Underlayment is a layer of a metal roof that homeowners rarely see, so understanding it helps a Princes Lakes homeowner appreciate a quality roof. Here is what it is.
A Layer Beneath the Panels
Underlayment is a material installed over the roof decking and beneath the metal panels, forming a layer between the structure and the visible roof. It is a standard, important part of a metal roof assembly, sitting out of sight under the metal. While homeowners see the panels, the underlayment beneath plays a real role in the roof's performance. It is an integral component of a properly built metal roof. It works unseen beneath the surface.
A Secondary Moisture Barrier
The underlayment's main role is to serve as a secondary barrier against moisture, protecting the roof deck and home if water ever gets past the metal panels. While the metal is the primary defense, the underlayment provides backup protection should any moisture penetrate, from wind driven rain or other causes. This secondary barrier is a key reason underlayment matters. It adds a layer of protection beneath the panels. It safeguards against moisture intrusion.
Protecting the Deck
By providing this barrier, the underlayment helps protect the roof deck, the sheathing the metal is attached to, from moisture, which supports the structure's integrity and longevity. Keeping the deck dry is important to the roof and home, and the underlayment contributes to that. Protecting the deck is part of the underlayment's value. It helps keep the roof's structure sound over time. It defends the deck beneath.
Part of the Assembly
Underlayment is one component of the metal roof assembly, working with the panels, fasteners, and other elements to create a complete, watertight roof. It is not optional in a quality installation but a standard, important part of doing the roof correctly. The underlayment plays its role alongside the other components. It is part of what makes a metal roof a complete, protective system. It contributes to the whole.
What It Is, in Short
Underlayment is a material installed over the decking and beneath the metal panels, serving as a secondary moisture barrier that protects the roof deck and home if water gets past the metal. It is a standard, important part of a quality metal roof assembly.
One point worth making clear for Princes Lakes homeowners is that the underlayment, although it is a layer you will never see once the roof is finished, is a genuine part of what makes a metal roof perform and last, and it is worth understanding for what it tells you about the quality of an installation. The underlayment is the material that goes down over the roof decking, the plywood or sheathing that forms the roof's surface, before the metal panels are installed on top. Its primary job is to serve as a secondary barrier against moisture, a backup to the metal panels themselves. The metal is the roof's main defense against water, and a properly installed metal roof sheds rain and snow effectively, but the underlayment provides insurance, so that if water ever does get past the panels, from wind driven rain forcing moisture under an edge, from ice, or from any other cause, the underlayment helps keep that moisture from reaching the deck and the home below. By keeping the deck dry, the underlayment also helps protect the structural sheathing the roof is built on, which supports the roof's and the home's longevity over the decades a metal roof serves. Underlayment also provides a smooth, consistent surface over the decking for the panels to be installed on. For metal roofs specifically, there is an added consideration, because metal panels can get quite hot in the sun, the underlayment beneath them needs to be able to withstand that heat, which is why high temperature rated products matter. A quality installation includes proper, appropriate underlayment as a matter of course, so it is a reasonable thing to ask a contractor about when gauging whether they do things right.
It also helps Princes Lakes homeowners to know that underlayment has evolved, and that modern synthetic underlayments have largely become the standard for quality metal roof installations, which is worth understanding when comparing what different contractors propose. For many years, the traditional underlayment was felt, an asphalt saturated material that provided a basic moisture barrier and served adequately, and felt is still used in some applications. But synthetic underlayments, made from durable engineered materials, have become the common choice for quality metal roofing because they offer real advantages, they are generally more durable and far more resistant to tearing than felt, they hold up better over time and under the conditions beneath a roof, and they handle the heat that builds under metal panels well when a high temperature rated product is chosen. In addition to synthetics, there are self adhering membranes, sometimes called peel and stick, which adhere directly to the deck and form a sealed barrier, providing especially strong moisture protection and the ability to seal around fasteners, and these are often used in particularly vulnerable areas or wherever extra protection is warranted. The practical takeaway for a homeowner is not that they need to become an expert in underlayment products or specify them personally, but rather that an experienced, reputable metal roofing contractor will select an appropriate, quality underlayment for the roof, commonly a durable, high temperature synthetic, with added protection where it makes sense, and will install it correctly with proper overlap and detailing. The underlayment a contractor uses and how they install it is one of the quiet indicators of whether they build metal roofs to a high standard or cut corners on the parts that do not show.
One point worth making clear for Princes Lakes homeowners is that the underlayment, although it is a layer you will never see once the roof is finished, is a genuine part of what makes a metal roof perform and last, and it is worth understanding for what it tells you about the quality of an installation. The underlayment is the material that goes down over the roof decking, the plywood or sheathing that forms the roof's surface, before the metal panels are installed on top. Its primary job is to serve as a secondary barrier against moisture, a backup to the metal panels themselves. The metal is the roof's main defense against water, and a properly installed metal roof sheds rain and snow effectively, but the underlayment provides insurance, so that if water ever does get past the panels, from wind driven rain forcing moisture under an edge, from ice, or from any other cause, the underlayment helps keep that moisture from reaching the deck and the home below. By keeping the deck dry, the underlayment also helps protect the structural sheathing the roof is built on, which supports the roof's and the home's longevity over the decades a metal roof serves. Underlayment also provides a smooth, consistent surface over the decking for the panels to be installed on. For metal roofs specifically, there is an added consideration, because metal panels can get quite hot in the sun, the underlayment beneath them needs to be able to withstand that heat, which is why high temperature rated products matter. A quality installation includes proper, appropriate underlayment as a matter of course, so it is a reasonable thing to ask a contractor about when gauging whether they do things right.
Get a Properly Built Roof
Princes Lakes Metal Roofing installs metal roofing with proper underlayment across Princes Lakes and Johnson County, building the roof correctly from the deck up. Call (765) 676-3491 for a free consultation on a quality metal roof with the underlayment it should have.