From durability to sleek looks, metal roofs offer a range of benefits for homes. To ensure they perform and look as they should—and to protect the premium investment—it’s important to design a roofing system and choose a metal roofing underlayment that effectively manages moisture and other environmental impacts from outside, and even inside, the home.

The Moisture Challenge with Metal Roofs

Metal roofing is impermeable, which helps it keep out bulk water but also means water vapor will not move through it and out of the roofing system. As such, this can cause condensation to build up underneath, particularly in modern homes with conditioned attics. The trapped moisture can combine with the cold temperature of the roof and corrode the metal over time.

For this reason, it’s important to design the roof system with ventilation underneath, which will allow for airflow that can dry out the underside. Designers can accomplish this in several ways, including double-strapping or using a ventilated underlayment like Cedar Breather. Cedar Breather decouples the metal from the roof sheathing, additionally helping to reduce noise transfer from rain and hail.

Why Choose a Self-Adhered Product for Metal Roofing Underlayment?

Along with proper ventilation, choosing the right underlayment is also key. VaporDry SA is a self-adhered, vapor-permeable underlayment with features that alleviate common concerns associated with other materials for metal roofing applications.

Vapor Permeability:

Common asphalt-based underlayments are vapor closed, which can lead to trapped moisture in the roof assembly, especially as more homes have conditioned attics. VaporDry SA is vapor permeable, with a rating of 14 perms, which allows interior moisture to escape to help maximize the roof’s drying potential.

Metal roofing can be installed directly to the VaporDry SA membrane, but for optimal drying, combine VaporDry SA with Cedar Breather and a ridge vent to create convective airflow that will promote drying out the underside of the metal roof.

Attachments:

Depending on the roofing type and manufacturer, metal panels may be attached with clips, battens, or other fastening systems. This adds up to a lot of penetrations that can allow air to enter the roofing envelope. VaporDry SA’s acrylic adhesive self-seals around fasteners, acting as an air barrier as well as a moisture control layer.

Smoother Surface:

Some underlayments have granules in the material that may scratch the underside of metal panels, leading to deterioration and potential rust over time. VaporDry SA’s surface is slipresistant without the use of coarse granules that can damage metal roofing.

Post-Storm Protection:

In the event of severe windstorms or hurricanes, missing roofing shingles and panels can leave a home exposed to the elements, potentially wreaking even more havoc on the structure. Unlike traditional stapled felt or paper, a self-adhered product like VaporDry SA isn’t prone to blow-off, helping to protect the sheathing underneath until it can be covered. In fact, VaporDry SA is tested up to 150 mph.

Protect the Metal Roofing Investment

Your clients’ investment in a metal roof reaps a variety of benefits in both form and function. Protecting that investment relies on a systems approach that considers what’s underneath as much as what’s visible. Upgrading to VaporDry SA for your metal roofing underlayment, in combination with Cedar Breather, can help keep the structure dry and preserve the longevity and performance of the roof system.

Experience VaporDry SA for yourself! Request a sample or get in touch with us for support and resources.