Roof flashings play a massive role in protecting your home from water leak damage. Thus, knowing how to cut roof flashing correctly is paramount for a proper installation.

In this guide, we’ll provide instructions on cutting roof flashing. From the right tools to the best cutting techniques, we’ll help you measure, prepare, and slice up new roof flashings for your home. Let’s get started!

What are the Best Tools for Cutting Roof Flashings?

The right tools and equipment are essential if you want to know how to cut roof flashing replacements for your home. So before you get started, make sure you have the following items nearby:

  • Tin Snips. Tin snips are the most commonly used tools for cutting metal flashings. These scissors come in different types, including straight-cut, left-cut, and right-cut snips, allowing you to make precise cuts according to your needs.
  • Utility Knife. A utility knife with a sharp, retractable blade is versatile, and it can also be used to cut various types of roof flashings, including rubber and plastic. Make sure to use a new, sharp blade to ensure clean cuts.
  • Aviation Snips. Aviation snips, or compound snips, are excellent for cutting thicker metal flashings. They have serrated jaws that provide better control and leverage, allowing you to cut through steel, aluminium, or copper easily.
  • Angle Grinder. An angle grinder fitted with a metal-cutting disc is a powerful tool for cutting metal flashings. It’s advantageous against any thicker or more rigid product. However, you should exercise caution when using this tool due to its high-speed rotating disc.
  • Electric Shears. Electric shears are designed specifically for cutting industry-grade metal flashings quickly and efficiently. They provide clean and precise cuts, especially for larger projects.

What Tool is Used to Bend Flashing?

The tool commonly used to bend flashing is the sheet metal brake or bending brake. This is a specialised device designed to create precise bends in metal, including various types of flashing.

Sheet metal brakes typically consist of a clamping mechanism, a bending leaf or beam, and adjustable stops for controlling the angle and length of the bend. By securing the flashing material in the brake and applying pressure, the bending leaf or beam allows for accurate and controlled metal manipulation.

Sheet metal brakes are available in various sizes and configurations. This allows for different bending capacities and applications.

Safety Precautions Before Cutting Roof Flashings

Before you start cutting roof flashings, it’s crucial to prioritise safety when cutting roof flashings. That way, you can prevent accidents and injuries. Here are some essential safety precautions to take:

  • Wear Protective Gear. Always wear appropriate safety gear, including safety glasses or goggles, work gloves, and sturdy footwear. This protects you from hazards like sharp edges, debris, or flying particles.
  • Secure Your Work Area. Ensure your work area is clear of any obstructions or tripping hazards. Remove debris and create a stable surface to work on. Use ladders or scaffolding properly and make sure they are stable and secure.
  • Check for Electrical Hazards. Before using power tools, check for overhead power lines and maintain a safe distance. Never work in wet conditions to minimise the risk of electrical shock.
  • Use Proper Techniques. Familiarise yourself with the correct cutting techniques for the specific flashing material you are working with. Also, follow the best safety rules when using machinery.
  • Avoid Excessive Force. Do not apply excessive force or rush the cutting process. Use controlled and steady movements to ensure accuracy and reduce the risk of slips or mishaps.
  • Handle Tools Safely. Handle tools carefully, keeping them in good condition and using them only for their intended purpose. Always follow the manufacturer’s instructions and guidelines for safe operation.
  • Seek Professional Help if Needed. If you encounter complex flashing configurations or need more clarification about the cutting process, find professional assistance. From knowing the Australian Standard AS 4024 to having the expertise and equipment, they can ensure safe and efficient cutting. A roofing expert can also advise if you can repair your current roof flashing instead of getting a new one.

Proper Measurement and Preparation

Next, you need to take measurements for the new roof flashings and prepare the spot where they will be placed. That way, you can guarantee a seamless installation and avoid wasting your time, energy, and resources. Here are some essential tips to follow:

  • Assess the Area. Thoroughly inspect the area where the roof flashing will be installed. Identify any obstacles, vents, or irregularities that may affect the measurements or cutting process. Take note of the required dimensions and shapes needed for the flashing.
  • Measure Twice, Cut Once. Measure the length, width, and any necessary angles of the flashing carefully. Use a tape measure or ruler to ensure accuracy. Double-check your measurements before making any cuts to save time and effort.
  • Mark the Cutting Lines. Once you have determined the correct sizes, mark the cutting lines on the flashing material using a pencil or marker. Use straightedges or templates to guide precise cuts, especially for complex shapes or angles.
  • Consider Overlaps. Depending on the type of flashing, you may need to account for overlapping joints. Measure and mark the areas where overlaps will occur, ensuring proper alignment and sufficient coverage for effective waterproofing.
  • Allow for Expansion and Contraction. Remember that some flashing materials, such as metal, may expand or contract with temperature changes. Leave a small gap or provide adequate allowances to accommodate these movements.
  • Clean and Prepare the Work Area. Clear the work area of any debris, ensuring a clean and safe environment for cutting. Ensure the flashing material is securely held, using clamps or weights if necessary. This prevents it from shifting during the cutting process.

Best Cutting Techniques for Roof Flashing

Proper cutting techniques are also vital to achieve clean and accurate cuts. The specific method you use will depend on the type of flashing material. Here are some best cutting techniques for roof flashings:

Straight Cuts

This technique allows you to cut straight lines in roof flashings. It’s a fundamental technique that every roofer should master. To achieve precise straight cuts, follow these steps:

  1. Secure the flashing material on a stable surface.
  2. Choose the appropriate cutting tool based on the material (see the list of tools above).
  3. Align the cutting tool with the marked cutting line.
  4. Apply steady pressure and make controlled cuts along the line.
  5. Make multiple passes if necessary for thicker materials.
  6. Inspect the cut edge for any burrs or rough spots.
  7. Use a file or sandpaper to smooth out the edge if needed.

Curved Cuts (for the Corners)

When dealing with curved edges or corners, try the following steps:

  1. Measure and mark the dimensions of the corner on the flashing material.
  2. Use a compass or a flexible template to draw the desired curved shape.
  3. Align the cutting tool with the marked curved line.
  4. Begin cutting along the curved line using small, controlled movements.
  5. Make adjustments as needed to achieve the desired curved shape.
  6. Check the cut for accuracy and smoothness.
  7. Repeat the process for each corner, ensuring consistency in the curved cuts.

Mitre Cuts

If your roof flashing requires angled cuts, mitre cuts are the way to go. Follow these steps:

  1. Measure and mark the length of the angle.
  2. Set the angle on a mitre saw or box according to your desired cut.
  3. Secure the flashing material in the mitre saw or box, aligning it with the marked cutting line.
  4. Hold the flashing firmly and cut the marked line, ensuring a smooth and accurate cut.
  5. Repeat the process for any additional cuts required.
  6. Inspect the cuts for precision and clean edges.
  7. Smooth any rough spots or burrs using a file or sandpaper if necessary.

How Do You Cut Corrugated Roof Flashing?

When cutting corrugated roof flashing, it’s essential to use the appropriate tools and techniques to ensure accurate cuts without damaging the material. Follow these steps:

  1. Measure and mark the desired dimensions on the corrugated flashing.
  2. Use tin snips with a serrated or notched blade to cut corrugated materials.
  3. Align the cutting blades with the marked cutting line, ensuring a firm grip on the flashing.
  4. Make short, controlled cuts along the corrugations, following the marked line.
  5. Work your way along the cutting line, gradually separating the corrugated sections.
  6. Do not apply excessive force, as it can bend or distort the corrugations.
  7. After cutting, inspect the edges for any roughness or sharp burrs and smooth them if necessary.

Other Tips When Cutting Roof Flashings

In addition to the cutting techniques above, here are some additional tips to keep in mind:

  1. Take breaks as needed. Cutting roof flashings can be a physically demanding task. Take breaks to rest and avoid fatigue, which can lead to mistakes or accidents.
  2. Practice on scrap material. If you’re new to cutting roof flashings, practice on scrap material first to get a feel for the tools and techniques before working on the actual flashing.
  3. Properly prepare the end wall and sidewall. Start by measuring the width of your sidewall trim. Then mark the width of your sidewall on the end wall, and draw a line to the corner.
  4. Be gentle with the snips. When using tin snips to cut metal roof flashings, avoid closing them all the way down. Doing so will make your cut look choppy and uneven. Instead, leave the snips around a quarter of an inch open, then gently slide it inwards until you cut through.


By following our guide on how to cut roof flashing, you’ll gain the knowledge and techniques needed to achieve precise and professional results. Properly cutting roof flashings is essential for effective waterproofing and ensuring the longevity of your rain gutter and roofing system. So dive into the guide, follow the steps, and confidently equip yourself with the skills to tackle this vital aspect of home maintenance.

If you encounter any difficulties or have further questions or concerns, feel free to consult professional assistance. Their expertise can provide valuable insights and guidance, ensuring the best possible outcome for your roofing project.