We’ll be using a 10×10 shed to show you how to install a metal roofing. The shed has a simple gable roof that runs down the middle of the structure with a slope of 4:12. To attach the panel to the roof sheathing, we’ll use a standard raised-rib metal panel. This panel uses exposed fasteners.
Remember that OSB roof sheathing and plywood can be used to create a roof deck underneath your metal roof panels. A metal roof can be installed directly on top of either. It is important to make sure that they are at most 1/2 inch thick.
Furring strips can be used instead of plywood or OSB for a solid roof deck. Furring strips can be used if your shed is not heated. Furring strips can be used to heat your shed but they will increase the amount condensation that you have on your metal roof’s underside. They should therefore be avoided and replaced with a solid roof substrate.
Step 1: Prepare the Roof Surface
Metal roofing can be used over old shingles. You can use metal roofing over old shingles by using furring strips and waterproof barriers first. You can also screw through the shingles directly if you feel that this is too much and your shed is not heated.
Battens will reduce the weight of your structure, and increase the chance of condensation under your roof surface. However, battens are more affordable than solid decking, and they can be used to build a simple, unheated shed.
Unheated sheds do not require underlayment. Your metal panels can be attached directly to your sheathing.
Final, prepare the roof surface for your underlayment or metal roof panels. Plan any roof venting you plan to install. You can mark it, but don’t cut a hole. To ensure that the sheathing and the metal roof panels are perfectly aligned, you will cut your hole after the roof has been installed.
Step 2: Install the Underlayment and Edging
Follow the manufacturer’s instructions to install the underlayment. Install the eave edge edging first if you’re installing flashing to go with your metal roof panels.
Your eave edge edging should be fitted to your underside and onto your face. It should cover your entire eave. Attach the eave edge to the underside and flashing through the lip. Next, nail the faces using stainless steel finishing nails in the same color as the flashing.
Install your underlayment to cover the edge of the eave. The rake edge should be installed over the underlayment. The rake edging attaches the same as the eave edge edging except that you use roofing screws for the face screwing of the rake flashing. Make sure the rake flashing’s eave ends are over the eave.
Some rake edging may be applied over metal panels that have been installed. Install the metal panels first, and then the rake edge. It all depends on the manufacturer of the metal roofing panel.
Step 3: Install the metal roof panels
The type of metal roof panel you choose will determine how it is installed. Start at the edge, and ensure that your first panel covers the existing edging by 1 inch. If you don’t have gutters, run your first panel flush to the roof edge and 1″ above the eave.
The metal panel’s top should not be more than 12 inch below the peak of your gable roof. Follow the manufacturer’s instructions to install your panels. For more information on how many screws you should use, see the above. Our rule was 80/square of roofing.
When screwing into the ribs of the metal panels, make sure you don’t go too far or damage the rib. Also, do not compress the Neoprene washer too much. Metal lap screws can be used to connect metal panels that overlap at the rib. They do not penetrate the sheathing. These screws can also be used to edge roofs.
Apply mastic tape or sealant if your metal roof product states that you will need it. It is best to take your time as the tape can be tricky to work with.
Your final roof piece will likely need to be cut in lengthwise to fit your shed roof. A circular saw fitted with a metal cutting knife is a good choice. Tin snips can be used, but it is difficult to cut long pieces.
Step 4: Position and Fix Venting
After your metal panels have been installed, it is time to make any necessary holes for your chimney, roofing venting or other outlets. You will need a jigsaw and a metal cutting knife. They have many small teeth. You can also use power shears and tinsnips but then you will need to use another saw to cut through the roof sheathing.
Make sure you use lots of silicone when installing your chimney or vents.
Step 5: Install Ridge Cap
The final step is to install a ridge cover over your metal roof’s gable. Each manufacturer has a different ridge cap that they recommend for their corrugated panels. You should follow the instructions provided by the product.
If you don’t have the directions, you will need to first know that the cap covers each side by 6” and each end by 1.
Make two opposing angles of one inch at each end of the cap. This will result in a triangle being cut. To determine the angle of your roof pitch, use a speed square. Use a pair of sheet metal bending scissors to bend each side. Two flaps of one inch will be left that can fit over the tops of the rakes either side of your gable.
As directed by the manufacturer, use butyl tape, foam and sealant. Apply the tape to one side of each gable, just above the edge where the ridge caps will be. Next, place the foam on the tape and then seal the foam with silicone sealant.