Protecting the beauty and longevity of metal roofing requires attention to detail underneath, including creating proper spacing and drainage to keep things dry. There are several methods for creating an airspace, including adding double-strapping to the roof system.

Why is an Airspace Important Under Roofs?

Condensation can occur on the underside of roofing materials like metal, tile, and wood. When that condensation combines with cold air, it could corrode or decay the roofing material. By designing a system with an airspace between the roof deck and the roofing, trapped moisture can dry out or more easily drain away.

Best Practices for Using Double-Strapping for Roofs

Double-strapping is one method for creating an airspace. Much like furring strips or Batten UV in a wall system, double-strapping separates the roofing material from the sheathing to create an airspace.

Install VaporDry SA roofing underlayment on top of the roof sheathing; as a self-adhered product, VaporDry SA self-seals around fasteners—for both the roofing material and the added strapping—providing an air control layer as well as a moisture control layer. It also is vapor-permeable, allowing moisture from the attic to migrate and increasing drying potential of the roof deck.

It’s important to install the first layer of 1-by strapping parallel to the rake to create vertical channels that will ensure proper airflow and moisture drainage. Then install the second layer parallel to the eave.

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Alternatives to Double-Strapping

Another way to create an airspace under the roof is to apply VaporDry SA roofing membrane on top of the sheathing, then Cedar Breather roof ventilation mat. Cedar Breather adds a rainscreen between the roof deck and the panels; when combined with a ridge vent, this helps create convective airflow to help dry out the space.

Cedar Breather also levels out imperfections in the roof, so it also can help address oil canning that sometimes occurs with standing-seam metal roofs.

Ensure the roofing fasteners and clips you use can accommodate the added thickness of the Cedar Breather.

Try VaporDry SA or Cedar Breather on your next project! Request a sample or get in touch with us for support and resources to help Transform Your Craft.