Direct-to-Deck vs Batten (Strapping) Metal Roofing: Why We Never Use Battens

Every metal roof we install goes directly on the roof deck, never on strapping. It’s the one thing we won’t change, and it’s the biggest difference between our roofs and many others. Here’s what direct-to-deck metal roofing means, and why it matters on an Ontario home.

What is batten (strapping) installation?

Some metal roofs go on battens, also called strapping. Installers nail wood strips in rows across the roof deck, then fasten the metal to the strips instead of the deck. As a result, there’s open space between the metal and the wood underneath. In fact, many tile- and shake-style metal products only work on battens.

What goes wrong in the gap

That open space is where the problems start:

• Condensation. Ontario swings between hot and cold, so moisture forms in the gap, much like dew on a car on a fall morning. It sits against bare wood, and over time the wood rots. We’ve torn off many strapped roofs for exactly that reason.
• Critters. The gaps make a sheltered home for raccoons and other animals. Here’s what raccoons can do to a roof.
• Noise. Metal spanning open gaps drums in the rain. Here’s why our roofs stay quiet.
• Dents. Step between the strips, and the metal can bend.

What direct-to-deck means

We fasten a direct-to-deck roof straight to the plywood deck. Alternatively, it can go over one or two layers of existing shingles when the deck is sound. Here’s how a metal roof over shingles works. Standing seam, however, always goes on a bare deck. On a bare deck, we also cover the entire surface with ice and water protection before the metal goes on.

There’s still a small pocket of air at each shingle, where the top of one shingle locks into the next. However, the interlock closes that pocket in. It’s not an open channel running across the roof, so moisture has nowhere to collect and animals have no way in.

Panels that lock on all four sides

Each panel locks to its neighbours on all four sides. Because of that, it’s hard for wind to catch an edge, and there’s no open seam for water to follow.

Fasteners you never see

The fasteners sit under the panel above, out of the weather. In contrast, many batten and basic metal roofs use screws through the face of the panel, with a rubber washer under each screw head. Over the years, those washers dry out and crack, and the screws work loose. Eventually, someone has to replace them, or each one becomes a spot where a leak can start.

Homeowners who call us after getting a quote for a batten roof tell us almost no one mentioned this maintenance. Hidden fasteners don’t have that problem. That’s why we call our 4-way locking, hidden-fastener roofs maintenance-free.

Is batten roofing ever the right choice?

On barns, sheds and some farm or industrial buildings, panels on strapping can make sense. On a home you plan to live in for decades, though, we won’t install one.