Use a measuring tape to determine the distance between the ridge and the eave of your roof. Add one or two inches to that measurement depending on how much overhang you want. Now measure the width of your roof in feet. Assuming your metal panels will have a width 36 inches (3 ft.) your next step would be to convert the measurement of your roof’s width to inches. Multiply the width of your roof by 12 then divide that number by 36. This will give you the number of panels you need. In this case, you’ll need 15 panels. Normally panels come in a width of 3 feet, but they can be cut to desired lengths. Give the measurements to a roofing distributor and order your panels. Install your underlayment. The underlayment will act as a waterproof layer under your metal roofing, which will prevent the underlying wood from rotting.
It’s recommended that you install a GAF DeckArmor breathable synthetic underlayment, and not felt or tar paper. Start installing your underlayment from the eave to the ridge with a one-foot overlap between each sheet. On steeper roofs, it won’t be necessary to have an overlap that’s greater than 6 inches. If you have a chimney, then run the underlayment to the base of the curb. Cut a piece of underlayment that is 4 feet wider than the chimney.
Place the underlayment 6 inches up the wall of the chimney with 2 feet flaps sticking out at each end. Nail the flaps down along the straight line of the fold, placing two nails at each end of the fold. Cut the corners at a 45-degree angle to your roof deck then wrap those corners around the chimney. Next, install your side flashing then top flashing in the same way the underlayment was installed. Lay down batten boards along the width of the roof. These help to fasten the steel panel to the roof deck.
From the eave to the ridge, place down 1-by-4-inch pine boards parallel to the ridge with 24 inches of space between each board from eave to ridge. Fasten the boards to the roof deck with screws using a drill. Install the eave flashing. This allows water to flow off the roof. Completely remove both the old eave flashing and any rotting wood and have them replaced. Next place your eave flashing up against the eave and hammer it into place with a nail. Each nail should be placed 8-12″ on center in a staggered pattern to enhance rigidity. Cover the entire width of your eave in this way and if there’s a guttering the eave flashing should conceal each side of the guttering.
Place closure strips onto the eave flashing then add butyl tape sealant over the closure strip. This will prevent pests and animals from getting into the gaps of the metal panels. Install your first metal panel. Now this is a crucial step in the installation of a metal roof. It will determine whether or not your roof is squared.
Place the first panel up against the edge of the gable, with a length of the panel hanging over the eave (3/4, 1, or 2 inches based on your preference). Fasten the metal panel into place by adding screws to each 1-by-4-inch pine board along the length of the roof deck. Place the second panel so that the ridge of the first panel overlaps with the ridge of the second panel.
Add screws a foot apart along these overlapping ridges from eave to ridge. Install the remaining panels in a similar manner. Spread a thin line of butyl tape sealant along the edge of the roof from eave to ridge. Place the gable over the side edge of the roof. Screw the gable trimming into the roof.
Next place the ridge cap over the ridge of the roof with the edge of the roof cap flush with one end of the roof peak. With a pencil and using the using the edge of the ridge cap as a guide, mark a line along the ridges of the installed roofing panels. Lift the ridge cap off the ridge and cut adhesive closure strips to match the shape of your roofing panels. Place these strips 1 inch above the pencil line on each side of the roof peak. Continue applying closure strips in this manner until you reach the other end of the roof. Remove any overhanging strips with a utility knife. Place the ridge cap back onto the roof peak with the edge of the ridge cap flush with the roof peak. Screw the ridge cap into place with each screw placed ½ inch above the edge of the ridge. Add a second segment of ridge cap to the end of the first cap with six inches of overlap between the two. Continue adding ridge cap sections in this manner until you reach the far edge of the roof peak. Add the final section by overlapping the excess portion over the previous section.