A leaking metal roof is a common issue in factories, warehouses, industrial facilities, and other large buildings. However, the point where water appears inside the building is not always the actual source of the leak. Water can travel along the roof surface or structural elements before becoming visible.
Therefore, before choosing a metal roof waterproofing solution, it is important to identify the actual source of water ingress and inspect the areas most likely to cause leaks. Here are 7 areas to check first when a metal roof is leaking.
1. Roof Screws and Fasteners
Roof screws and fasteners are among the first areas to inspect when investigating a metal roof leak.
Over time, fasteners can:
- Become loose due to vibration and roof movement.
- Corrode or deteriorate.
- Develop damaged or degraded rubber washers.
- Create gaps around the points where they penetrate the metal sheet.
Water can enter through these points and cause leaks in different areas inside the building.
Important: Simply tightening the screws or applying more sealant may not address the underlying condition of the roof and surrounding details.
2. Joints Between Metal Roof Sheets
Metal roofs are typically assembled from multiple sheets, creating overlapping joints and longitudinal seams. These areas can become vulnerable to water ingress if the installation, joint treatment, or sealing materials deteriorate over time.
Continuous exposure to sunlight, rain, and temperature changes can place stress on these joints, causing gaps or reducing their ability to prevent water penetration.
For older roofs, it is important to inspect the entire joint rather than only treating the area where water is currently visible.
3. Roof Ventilators and Other Roof Penetrations
Roof ventilators, ventilation pipes, service pipes, and other equipment penetrating the roof create junctions between different materials and the metal roof surface.
These areas can be particularly complex because they involve multiple materials, joints, and interfaces. If the sealing around these details cracks, separates, or deteriorates, water can enter the building.
For details such as ventilator bases and roof penetrations, waterproofing should address the entire junction area, rather than simply sealing one visible gap.
4. Roof-to-Wall Junctions
The junction between a metal roof and a wall, parapet, or vertical structure should also be inspected when investigating roof leaks.
These areas often include:
- Interfaces between different materials.
- Flashings.
- Joints and sealants.
- Corners and difficult-to-access details.
As protective materials deteriorate, water can enter from the roof edge and travel beneath the metal sheets.
5. Rooflights and Roof-Mounted Components
Rooflights, skylights, and other components installed on the roof can become potential sources of water ingress if their connections to the metal roof are no longer watertight.
Different materials can also respond differently to temperature changes. Repeated thermal movement can place stress on joints and sealing materials over time.
Therefore, both the surrounding roof surface and the junctions should be inspected rather than focusing only on the rooflight itself.
6. Gutters, Drainage Channels, and Roof Edges
Not every case of water entering a building originates directly from the metal roof surface.
Blocked gutters, standing water, or poor drainage can cause water to overflow into areas around the roof perimeter. Roof edges and termination details should also be inspected to identify potential water ingress paths.
For large industrial facilities, the drainage system should be assessed together with the roof surface during the inspection.
7. Areas That Have Been Repaired Before
Another area that deserves particular attention is any part of the roof that has previously been repaired or treated for leaks.
Applying additional sealant or coating over an existing repair may reduce water ingress temporarily, but if the underlying cause has not been addressed, the leak may return.
For an older metal roof, the inspection should consider:
- The condition of the metal sheets.
- Joints and roof penetrations.
- Existing coatings or waterproofing materials.
- The extent of roof movement.
- The actual scope of deterioration.
What Should You Do After Identifying the Cause?
Once the source of water ingress has been identified, the waterproofing approach should be selected based on the cause, roof condition, and scope of the problem.
When the Problem Is Limited to Specific Details
If the issue is concentrated around a roof ventilator, pipe penetration, joint, or other complex detail, the affected areas can be treated individually.
This is where Triflex ProDétail can be considered. It is designed for waterproofing complex roof details and difficult junctions.
When the Entire Roof Surface Has Deteriorated
If multiple areas of the roof are leaking, the existing protective layer has deteriorated, or leaks continue to recur across different areas, treating individual points may not provide a long-term solution.
In such cases, the feasibility of refurbishing and waterproofing the entire roof surface should be assessed.
Triflex Protect is a PMMA-based waterproofing solution for roof surfaces, using fleece reinforcement. It can also be combined with Triflex ProDetail to provide a coordinated solution for both the roof surface and complex details.
Why Should You Not Only Treat the Visible Leak?
One common mistake when dealing with a leaking metal roof is to focus only on the point where water appears inside the building.
However, the visible leak may not correspond to the actual point of water ingress. Water can enter through a joint, fastener, ventilator base, or another roof detail before travelling to a different location.
Simply applying more sealant to one spot may therefore provide only a temporary solution.
For industrial facilities, identifying the actual cause at the beginning can also help reduce:
- Repeated repair costs.
- Disruption to plant operations.
- Damage to equipment and stored materials.
- The risk of additional leaks developing over time.
Inspection Process Before Metal Roof Waterproofing
A proper inspection should begin with a comprehensive assessment of the roof, rather than focusing only on the reported leak.
A typical inspection process can include:
- Inspect the existing roof condition
Identify areas showing signs of water ingress, deterioration, or physical damage. - Check the 7 high-risk areas
Inspect fasteners, joints, roof penetrations, ventilator bases, roof-to-wall junctions, rooflights, drainage systems, roof edges, and previously repaired areas. - Assess the existing materials
Determine the condition and level of deterioration of the metal sheets and existing protective layers. - Define the required scope of work
Assess whether the problem requires localized detail waterproofing or full-surface roof refurbishment. - Select the appropriate waterproofing solution
The solution should take into account the roof structure, substrate, thermal movement, existing materials, and operational requirements of the facility.
Conclusion
When a metal roof is leaking, the first step should not simply be to apply more sealant. The priority is to identify where water is actually entering the roof system.
Once the cause has been identified, the appropriate solution can be selected based on the actual condition of the roof, from Triflex ProDetail for complex roof details to Triflex ProTect for full-surface roof waterproofing.
For industrial facilities, an effective waterproofing strategy should not only address the current leak but also provide long-term protection and reduce the need for repeated repairs.