You’ll need more than a pair of scissors for this DIY cutting job
Metal makes for a stylish, durable roofing material that protects your home and offers a unique look. DIY metal roof installation requires knowing how to cut metal roofing sheets to the correct size. Keep in mind that the cutting part of the project is relatively easy, but the cuts must be precise and well-planned to fit your roof and to prevent leaks and roof damage.
Additionally, the handling and cutting of metal roof panels needs to be done carefully and safely. Keep reading to learn how to cut metal roofing, including the tools and safety measures you need to take.
You should use certain tools to cut metal roofing to ensure it is done safely and properly.
Tin snips are essentially scissors for cutting metal. They are ideal for short, precise cuts or for cutting individual sheets by hand. You may wish to use multiple types of snips for this project:
Yellow or plain-tip snips cut straight lines.
Red left-handed snips cut counterclockwise so you can make rounded cuts to your left.
Green right-handed snips cut clockwise so you can make rounded cuts to your right.
These electric or pneumatic tools make straight cuts more quickly than tin snips and are one of the best ways to cut metal roofing. You may wish to invest in power shears or borrow some from a friend if you have a lot of metal sheets to cut. Tin snips, by contrast, are relatively inefficient for large projects and will take longer to get the job done.
Angle grinders are also called disc or side grinders. These electric or compressed air handheld tools have a metal cutting disc that rotates to cut, polish, grind, sharpen, and clean different materials. Angle grinders are designed to cut metal less than 2 ¾ inches thick. Their light weight and ease of use make them a portable and convenient choice for cutting metal roofing.
Circular saws offer some of the quickest cutting of metal roofing. However, they are more difficult to handle, so if you have little experience, one of the other tools on our list might be a better choice. The blades can also create enough friction to damage paint and protective coatings on the metal roofing.
Circular saws are more commonly used to cut wood, but when fitted with a carbide or steel blade, they make quick work of metal roofing. If you have a large roofing project and some experience with this tool, you will get it done more quickly using a circular saw.
Create a sketch of the top of your roof (as if looking down) to give you a visual of all areas. Measure the length and width of each roof section and write down the measurements. This includes roof features that may cover gables or cutout areas around skylights and chimneys—basically, anything that breaks up the flat surface of the roof.
Measure all sides of the roof even if they look like they are the same size. Looks can be deceiving, and older homes in particular may settle, creating different measurements from one side of the house to the other. Do not forget to measure hips (along the peak) and valleys (where different areas of the roof meet).
Use your measurements to calculate the total square footage of the roof and compare it with the metal roofing sheet measurements. Different brands and types of metal roofing panels come in different sizes. Determine the sheet size you need based on the material selected and roof measurements. You can reduce seams by buying metal roofing that is the same length as your roof. The total square footage you order should equal the square footage and then some to account for overlap and waste.
Do not forget to include the amount of overhang you want and the surface area of the eaves. If you have a steeper-than-average roof, you may need to consult local metal roof installers to get an estimate on extra material needed to account for the slope.
Finally, before cutting, make sure you have the following safety gear in place:
Safety goggles
Ear protection
Long sleeves and pants
Leather (or sturdy) gloves to protect your hands from sharp edges
Dust mask
Boots
Once you have donned protective gear, you are ready to cut. Do not rush, and follow your guidelines precisely.
You will need a flat, stable surface to work on, such as a sturdy workbench. Lay the metal roofing sheets on the surface with the underside of each sheet facing up, then hold them in place with adjustable clamps. The panel undersides are flatter than the top edges, which have ridges that stick up. Laying the sheets upside down will make straight cuts much easier. If you are installing a corrugated metal roof, it is important to overlap the sheets with at least two ribs—not just one—to prevent water from getting into the seams. For screw-down metal roofs, you should use seam tape.
Use the roofing calculations you took before purchasing your metal panels to determine how big each panel needs to be. Measure along the sides of your panel with a tape measure and use a permanent marker to mark where you will cut. Hold a combination square flush against the edge of the sheet and line it up with each mark. Use your marker to draw a straight guiding line across the entire sheet at each mark. You will follow these lines when making your cuts. Each mark and line you draw needs to be placed precisely to avoid gaps, leaks, and rust in your roofing, so double-check every measurement you make.
Straight, even cuts ensure that overlapping seams prevent water from getting under the metal sheets. If you are using corrugated roofing, you need two overlapping peaks—not just one. Make sure you put the metal sheeting on a stable surface, like a workbench.
Tin Snips
If you are manually making long, straight cuts, opt for large compound tin snips. Open the snips as wide as possible and make slow, methodical cuts while following your guide lines. Use the hand that is not holding the snips to pull up on the cut-off strip, rolling it to the side so it does not bind the handle.
Use green- or red-handled snips to cut in a circle—clockwise with green or counterclockwise with red. These snips let you cut holes for vent pipes and other roof features.
Power Shears
Power shears work well for all kinds of cuts, but especially in tight spaces and round cuts. These powered tin snips save time and some manual labor. Make sure you have marked your guide lines, line up the power shears, press the trigger, and stay on target. If the shears get stuck, turn them off and cut from the other end of the sheet metal, meeting your first cut in the middle.
Angle Grinder
You have to take a slightly different approach when using an angle grinder. Instead of making the cut in a single pass, you make several shallow cuts, one on top of the other, to prevent cutting on a curve or bending the blade. The shallow cuts let you maintain control and precision throughout the cutting process.
Circular Saw
Place the sheet metal on a raised surface. Put a metal-cutting blade, either carbide or diamond, on the circular saw. Set the blade depth and follow the guiding lines to cut the sheet.
You may need to create an opening in the middle of one of your metal pieces, such as for a vent pipe. Measure where the hole needs to go and trace the object with your permanent marker. Then punch a pilot hole using an electric drill fit with a half-inch metal-cutting drill bit. With your pilot hole cut, you can fit a pair of tip snips into it and slowly cut along the guide line. Alternatively, you can use an electric drill nibbler tool or attachment. Like a saw or power shears, start at your pilot hole and push the nibbler forward to follow the guide line.
A new metal roof, on average, costs $13,200. Depending on the size of the roof and the materials used, doing it yourself can cost anywhere from $2 to $25 per square foot, plus the cost of underlayment. The cost to install a metal roof using professional labor ranges from $5,700 to $16,140, on average, so you can potentially save more than $3,000 by making it a DIY project.
You might also have to factor in things like drip edge costs if you are making additional changes to the roof. In some cases, you can save money by installing the metal roofing over shingles, but consult a professional to see if this is a wise option for your home.
It is worth noting, however, that while cutting metal roofing yourself is a simple task, successfully installing that roofing is a serious job that can be dangerous for you and for your home if done improperly. For most homeowners, the best approach is to hire a local roofing company that installs metal roofing, especially if you want to do a whole roof replacement.
Standing seam metal roofs require special tools and, unless you know what you are doing, one simple error can lead to a major leak. Unlike shingles, metal roof repairs are extremely expensive, and many professionals may not even repair a metal roof that they did not install.
While a high-speed circular saw will cut through metal, and even cut through multiple sheets at once, the fast-spinning saw blades create a lot of heat. This heat can damage paint and other protective coatings, leading to serious problems like rust over time. The cost to paint a metal roof again to avoid this damage is typically an additional $0.50 to $1 per square foot.
It is not always necessary to put wood stripping (also called furring strips) under a metal roof, but some metal roofs require stripping to work efficiently. For example, you must use furring strips when installing metal over shingles in order to connect the shingles to the metal roofing. These strips are made of metal or wood. They create thermal breaks and provide a solid frame to which you can attach the metal roofing. A lack of wood stripping can cause condensation issues under certain roofs, so use the roofing manufacturer’s specifications as your guide.
There are advantages and disadvantages to metal roofs in cold climates. Metal roofing stands up extremely well to harsh winters as long as it is properly insulated. Snow and ice slide right off residential metal roofs, preventing the formation of ice dams; but because of this, they may require snow guards, which prevent the ice and snow that slide off a roof from causing a sort of "mini avalanche" that can damage property and people below.
The average roof requires about 17 metal sheets, but that varies according to house size and roof style. Each roofing sheet takes about five minutes to measure and cut, though this depends on your level of experience. If your roof has a steep slope, gables, and skylights, for example, it may require extra sheets to account for waste. Roofs with a steep slope over 3:12 typically require more sheets because the pitch adds extra inches. How much exactly you will need depends on the height versus the width of the roof. If you are unsure of the calculations, check with a local roofing professional.
