Winter Construction Metal Roof

This is a builder forum discussion rather than news, so it won't apply directly to most homeowners, but it offers a useful peek at what goes into a well-built metal roof if you're ever planning new construction or a major roof replacement.

A homeowner building a new house in Edmonton, Alberta asked about installing a metal roof in winter. The roof design included thick insulation (rockwool batts filling 16 inches of a 24-inch-deep roof cavity, leaving an 8-inch vented air gap), a vapor barrier, resilient channel (metal strips meant to reduce sound transfer) under the drywall, and plywood sheathing under the metal panels. The questions covered which underlayment (the protective layer between sheathing and metal roofing) to use, whether that underlayment needs to let moisture pass through, whether extra soundproofing was needed, and whether half-inch or five-eighths-inch plywood sheathing made more sense.

An experienced contributor answered that a mechanically fastened synthetic underlayment rated for metal roofs works fine, and that letting the underlayment "breathe" isn't necessary here because the plywood can already dry out into the vented air space below it. On soundproofing, he noted the resilient channel might not do much good in this layout, since the gap it creates could let sound sneak sideways between rooms instead of blocking it. He recommended five-eighths-inch plywood over half-inch, if the budget allows.

For most readers, the specifics are niche, but the exchange is a reminder that details like ventilation gaps, insulation depth, and sheathing thickness all affect how well a roof performs for decades.