When working with metal roofing and wall panels, trim and flashing are critical elements that ensure your roof is both watertight and durable. End wall trim, in particular, is designed to flash from the high side of the metal roof panels to a vertical wall, providing protection against water infiltration. Proper installation of trim and flashing requires attention to detail, correct overlaps, and the right sealing methods.
This guide covers the process of preparing and installing end wall trim, working with sidewall conditions, using foam closures, overlapping sections, and fastening techniques. It also includes important considerations for replacing or adding flashing during re-roofing projects.
Preparing the End Wall at the Sidewall
Before fastening the end wall trim, all sidewall trim must be installed. Begin by measuring the width of your sidewall trim — in this example, the sidewall trim is 6 inches. Mark the width of your sidewall on the end wall and draw a line to the corner section. Using metal cutting snips, cut along the line.
For cleaner cuts, avoid closing the snips completely on each cut. Instead, leave about a quarter inch of the snips open, sliding forward and repeating until the cut is complete. This technique ensures a smoother and more precise cut.
Installing Foam Closures and Sealants
Foam closures for the end wall should be placed 1 inch from the edge of the trim, secured with double-sided butyl tape. Apply silicone sealant onto the foam closures and also at the top of your sidewall. This helps to create a watertight seal and prevent leaks.
Overlapping the End Wall
End wall overlaps should be at least 6 inches. Mark the edge of your end wall accordingly and cut an eighth of an inch deep along the trace to notch out the hem. Pry open the hem 6 inches deep, allowing the upper section of end wall trim to slide into the lower notched section. Apply silicone sealant to all overlaps before fitting the pieces together.
Fastening the End Wall
Fasten the top section of the end wall with pancake screws placed 1 inch from the edge and spaced 12 inches apart. For the lower section, use lap screws, also 1 inch from the edge, following the path of the foam closures. Screws should be positioned on the high seams of your roofing panels, approximately 12 inches apart. At overlaps, use both pancake screws and lap screws for a secure hold.
It is essential to clean all metal burrs and shavings immediately after fastening, as they can rust overnight. If the installation takes multiple days, clean the roof after each workday.
Flashing Basics and Common Issues
Flashing is designed to direct water away from critical roof and wall intersections. In older roofs, flashing sizes were typically made for 5-inch exposure shingles. Modern shingles often have 5⅝ to 6-inch exposures, which can create gaps if the flashing is not replaced or extended during re-roofing.
If existing flashing is too short, water may bypass it and enter under the shingles, causing leaks and deck damage. Adding or replacing flashing ensures that water is directed onto the roof surface instead of underneath.
Things to consider in flashing metal roof
Always follow safety guidelines, store materials properly, and prepare the right tools before starting.
Product Information
Review the manufacturer’s product details to ensure compatibility and correct installation.
Roofing Anatomy / Side Trim
Understand roof components and the role of side trim in sealing and finishing edges.
Measuring Your Roof
Accurately measure roof dimensions to avoid material shortages or waste.
Roofing Installation / Felt / Cutting Panels
Install underlayment, cut panels to size, and prepare for precise placement.
Radiant Barrier
Add a radiant barrier to improve energy efficiency and reflect heat.
Purlin Installation
Install purlins to provide a solid, level base for attaching panels.
Drip Edge Installation
Attach drip edges to guide water away from the roof and prevent rot.
W Valley Installation
Install W valley flashing to channel water away from roof intersections.
Fastening Schedule / Proper Screw Installation
Follow the fastening pattern and screw placement for secure, leak-free panels.
Pre-drilling Panels / Overlapping Panels
Pre-drill for clean fastening and overlap panels correctly for watertight joints.
Squaring Panels
Ensure panels are squared to keep rows straight and avoid alignment issues.
Transition Flashing Installation
Install transition flashing to join different roof pitches or materials securely.
Endwall Installation
Fit endwall flashing to seal where the roof meets a vertical wall.
Sidewall Installation
Install sidewall flashing to protect the joint between wall and roof panels.
Gable Trim Installation
Attach gable trim to finish roof edges and protect from wind-driven rain.
Hip Cap Installation
Install hip caps to cover and protect the roof’s hip joints.
Ridge Cap Installation
Secure ridge caps to seal the peak of the roof against water entry.
Roof Boot Installation
Install roof boots around penetrations to prevent leaks.
Special Trim Information
Follow specific instructions for unique trim profiles and shapes.
Care and Maintenance
Inspect regularly, clean debris, and perform timely repairs to extend roof life.
Common Flashing Problems and Solutions
| Problem | Cause | Solution |
|---|---|---|
| Flashing too short for modern shingles | Older flashing designed for smaller exposures | Replace with longer flashing or add extension pieces |
| Water leaks at flashing seams | Improper overlap or missing sealant | Ensure overlaps are sealed and minimum 4-inch coverage is maintained |
| Improper water direction | Flashing bent or positioned incorrectly | Reposition flashing to direct water away from walls and joints |
| Rusting or deterioration | Old mill finish or lack of maintenance | Replace with corrosion-resistant metal and maintain regularly |
| Blocked water flow | Debris or incorrect trim design | Keep flashing areas clear and ensure smooth flow direction |
Importance of Proper Flashing Installation
During repairs or re-roofing, flashing should always be evaluated and, if necessary, replaced. Even if full removal of siding isn’t practical, additional pieces of flashing can be tucked under the existing setup to improve coverage. This is especially important in areas where water naturally concentrates, such as at sidewalls, valleys, and roof transitions.
Incorrect flashing placement can lead to water flowing under shingles instead of onto them. Once water penetrates the roof deck, it can cause rot, mold, and structural damage. By thinking ahead about how water flows and ensuring flashing is correctly sized and positioned, many common roofing problems can be avoided.
Correcting a Poor Flashing Installation
In some cases, flashing is installed with excessive coverage in less important areas while leaving critical joints exposed. A better approach is to prioritize areas where water can back up, such as against walls or at slope transitions. This may require lifting siding, adding ice and water barriers, and installing properly bent metal flashing that directs water away from the structure.
Final Thoughts
Trim and flashing are not optional decorative elements — they are functional, protective components that extend the life of your roof. Whether you are installing new metal roofing or re-roofing over existing materials, taking the time to measure, cut, seal, and position flashing correctly will prevent costly water damage in the future. As with all roofing work, attention to detail and an understanding of water flow are the keys to long-lasting results.
Hello! I’m Abdullah, a passionate professional in the field of construction and roofing. I am the proud owner of SJ Roofing & Venting, a leading construction company based in New York. With years of hands-on experience, I write about various construction methods, techniques, and industry insights to share my knowledge and help others in the field. I’m also the founder and main contributor of this website.