New build metal roof in light grey standing seam, Georgian Bay

Why a new build is the best time for a metal roof

On a re-roof we work with whatever the house already has: the old roof boards, the existing vents, flues where somebody put them decades ago. On a new build none of that is fixed yet. The roof boards go down new and flat, the ventilation path from soffit to ridge can be designed in, and penetrations can be grouped or moved so they do not land in a valley or right above a door.

There is no tear-off and no question of going over shingles. The roof goes on once, over new boards and high-temperature underlayment, and the conversation is about getting the details right rather than working around old ones.

Light grey on a new house

Most of the metal roofs going on new homes right now are charcoal or black. This one is light grey, and it suits the building: it picks up the greige board-and-batten siding, lets the black window frames and dark garage doors do the contrasting, and keeps a big, steep roof from looming over the driveway.

Light colours also have practical advantages. They are the most forgiving finish on metal: they show the least oil-canning on long, flat panels, they hide fading because there is little pigment to lose, and they run cooler in summer sun. On a roof with long, uninterrupted planes like this one, that forgiveness is worth something.

The dormer

The gable dormer is the one place where this roof stops being simple. It sits in the main roof plane above the garage, so the panels running down from the ridge have to stop above it, pick up again on each side, and meet the dormer's walls in a clean line. The water coming down the slope above has to be turned around the dormer, not driven into it.

On jobs like this our crew bends the flashings and trim on site, so each piece is made to the dormer as built rather than as drawn. Framing on a new house is rarely exactly to the drawings, and trim made in a shop weeks earlier is a common reason dormer flashing ends up caulked instead of folded.

Working alongside a builder

The photo was taken while the yard was still bare dirt and gravel, which is typical: the roof goes on as soon as the house is closed in so the interior trades can work in the dry. That means the roofer needs to be booked early and needs a clear path for the forming machine. Our panels are roll-formed on the driveway in one length from ridge to eave, so there are no horizontal laps even on a tall roof.

The Georgian Bay shoreline gets heavy lake-effect snow and strong wind off the water. Clip spacing is set to the site's ground snow load, and snow retention is worth deciding at the drawing stage, especially over garage doors and entrances, so it can be placed where the snow actually comes off. Gauge, seam, finish, underlayment, flashing, ventilation and warranty are all set out in a written specification before anyone commits.

What to settle before the roof goes on

If you are building, or working with a builder, these are worth agreeing on early:

• Where the flues, plumbing vents and any exhaust fans come through the roof.
• How the attic or roof assembly is ventilated, intake and exhaust.
• Where snow will slide off, and whether doors or walkways sit below it.
• Colour, chosen from a physical sample outdoors, not a screen.
• Whether solar might go on later, so seams and layout suit it.