How to Insulate a New Corrugated Metal Roof

If you are putting a new corrugated metal roof on a shed or garage, you may want to take some time to insulate it. Rather than simply attaching corrugated metal roofing to the roof joists, adding some roof sheathing and insulation will greatly increase the overall R-value of the roof.

Adding insulation to your corrugated metal roof is best done before the roofing is laid. For this reason, plan on choosing a day to lay the roofing where it is unlikely to rain, allowing you extra time to add sheathing and the other components of an insulated corrugated metal roof.

Step 1: Install a layer of plywood over the roof joists using galvanized roofing nails spaced every 8 inches. Lay the boards so that they are perpendicular across the roof joists. Not only will this allow you to move easily over the roof when installing the metal roofing, but it will also provide a base for your insulation.

Step 2: Apply a layer of roofing paper over the roof sheathing. This will help stop any leaks. You should plan on overlapping any building paper by 6-8 inches. Attach the roofing paper to the roof with galvanized roofing nails spaced every 8-12 inches.

Step 3: Add a layer of rigid foam insulation over the roofing paper. This type of insulation comes in sheets. Don't overlap the insulation, but do be sure to butt the seams together. Nail them down with your roofing nails spaced every 8-12 inches.

Step 4: Cover each seam in the rigid foam insulation with duct tape. This will help prevent any moisture from seeping in between the insulation panels. Sealing cracks will also increase the overall R-value of the insulation.

Step 5: Install the corrugated roofing panels over the insulation, following the manufacturer's instructions.

TIP: Try using a chalk line to mark the location of the roof joists. This will allow you to firmly attach the corrugated roofing panels to the underlying structure of the roof, rather than attaching the metal corrugated roofing panels to the wood sheathing.