A Guide to Flawless Metal Roofing: Avoiding Costly Fabrication & Installation Errors
Learn how to navigate the critical details of metal roofing—from screw selection to maintenance—to ensure your investment delivers decades of performance and avoids premature failure.
Metal Roofing: Common Fabrication Mistakes and How to Avoid Them
Metal roofing is a popular choice for industrial, commercial, and residential buildings because of its durability, long service life, and energy efficiency.A properly selected and installed metal roof can last for 20 to 30 years or even longer.However, the success of a metal roof doesn’t just depend on the quality of the materials; it heavily relies on correct fabrication and installation.Even small mistakes can lead to premature failure, turning a long-term asset into a costly liability.
This guide highlights critical mistakes commonly made by fabricators and contractors and provides practical tips to ensure your roof is long-lasting, leak-proof, and corrosion-resistant.
In This Article
- 1. Incorrect Measurements and Panel Selection
- 2. Choosing the Wrong Screws
- 3. Not Selecting the Right Roofing Sheet
- 4. Mishandling Sheets During Installation
- 5. Not Removing Guard Film After Installation
- 6. Incorrect Sloping and Poor Drainage
- 7. Using Improvised vs. CNC-Fabricated Accessories
- 8. Ignoring Thermal Expansion and Oil-Canning
- 9. Not Hiring Experienced Roofing Contractors
- 10. Lack of Regular Maintenance
1.Incorrect Measurements and Panel Selection
One of the most fundamental yet costly errors is getting the roof measurements wrong. Incorrect calculations can lead to a cascade of problems, including:
- Improper overlaps and visible seams.
- Uneven cuts, material wastage, and additional joints that become potential points for leaks.
Another common oversight is choosing the wrong panel type for the roof’s slope or application.For example, through-fastened corrugated panels are generally suitable only for steep slopes (≥ 4:12), whereas standing seam panels are a better choice for low-slope roofs because they accommodate thermal movement and feature concealed fasteners.
✅ Professional Tip
Always verify actual field measurements before fabrication and choose panel types based on the roof’s pitch, drainage conditions, and environmental exposure to ensure proper performance.
2.Choosing the Wrong Screws
This is one of the most underestimated but crucial aspects of a metal roof’s longevity.Many contractors use low-cost, unbranded screws that corrode quickly, causing leaks and staining.Even if the sheet is premium quality, the wrong screw size or an under-rated corrosion coating can lead to premature fastener failure.Screws may only account for 2-3% of the total roofing cost, but fastener failure is a top reason for leaks.
✅ Professional Tip
- Use self-drilling screws with EPDM washers designed for metal roofs.
- For coastal or highly corrosive environments, choose stainless steel screws or Class 3/4 coated screws.
- Never mix fastener grades with incompatible sheet coatings to prevent galvanic corrosion.
3.Not Selecting the Right Roofing Sheet
One size does not fit all when it comes to roofing sheets.The selection must be carefully based on location, expected lifespan, and coating grade.For example, buildings near the sea need higher-grade coatings (like AZ150 / AZ200) to combat salt corrosion, while a temporary shed might only need a basic coating (like AZ50 / AZ70). Our colour coted roofing sheets come in various grades to match your project’s specific needs.
✅ Professional Tip
Always discuss your project requirements with the supplier.A premium sheet may be unnecessary for one project, and a cheaper option may fail quickly in aggressive environments.
4.Mishandling Sheets During Installation
Scratches during unloading and installation are a leading cause of early corrosion.Even a minor scratch can expose the bare metal, allowing rust to start.
✅ Professional Tip
Train workers to handle sheets carefully and avoid dragging them.Consider using guard-film coated sheets, which protect the paint surface during installation.While this adds 3–4% to the sheet cost, it significantly reduces the long-term corrosion risk.
5.Not Removing Guard Film After Installation
One of the biggest mistakes is leaving the protective guard film on the sheet, assuming it extends its life.In reality, it does the opposite.Dust and water get trapped under the film, which damages the paint and accelerates corrosion.
✅ Professional Tip
The guard film is for temporary protection only.Remove it immediately after installation.
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6.Incorrect Sloping and Poor Drainage
Improper slope leads to water stagnation, which accelerates corrosion and can cause leaks.
✅ Professional Tip
Follow recommended slope guidelines (e.g., ≥ 3° for standing seam and ≥ 5° for corrugated panels) and ensure proper guttering to avoid ponding.
7.Using Improvised vs. CNC-Fabricated Accessories
To save costs, many contractors bend accessories like ridges and flashing manually on-site.This leads to poor alignment and water leakage through gaps.
✅ Professional Tip
Always use professionally fabricated accessories made with CNC machines for a precision fit and better sealing.
8.Ignoring Thermal Expansion and Oil-Canning
Metal expands and contracts with temperature changes.Ignoring this can lead to buckling, visible waviness (oil-canning), and stress cracks around fasteners.
✅ Professional Tip
Allow for expansion gaps and use clips that accommodate movement.Choose tension-leveled, ribbed, or thicker gauge panels to minimize oil-canning.
9.Not Hiring Experienced Roofing Contractors
Metal roofing installation is a specialized skill.Inexperienced contractors often make errors like over-tightening screws, misaligning panels, ignoring sealing details, and failing to follow manufacturer guidelines.
✅ Professional Tip
Always hire contractors with proven experience in metal roofing installation.
10.Lack of Regular Maintenance and Pre-Monsoon Checks
Even well-installed metal roofs need regular inspections and cleaning.Dust, leaves, and debris can block drainage, and loose screws or damaged sealants need to be detected early to prevent leaks.
✅ Professional Tip: Pre-Monsoon Checks
Project owners should insist on annual or bi-annual maintenance checks.Clean roof surfaces and gutters at least once or twice a year, inspect screws and joints, and touch up any minor scratches before heavy rains.
Build a Roof That Lasts a Lifetime
Metal roofs can deliver decades of reliable service if designed, fabricated, installed, and maintained properly. Small details like choosing the right screws, selecting the appropriate coating grade, and annual maintenance can be the difference between a roof that lasts 5 years and one that lasts 50.
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