1. Introduction
With global photovoltaic (PV) installed capacity continuously rising, rooftop PV has become a crucial method for energy transition in both residential and commercial sectors. Whether it’s residential roofs in Europe, commercial buildings in the US, or factory workshops in Southeast Asia, solar pitched roof mounting systems are widely used.
In these systems, the solar hanger bolt plays a pivotal connecting role: it supports the PV mounts and modules above and connects to the roof beams or purlins below. However, the “penetration installation” of hanger bolts introduces a key challenge: waterproofing.
If waterproofing fails, it can lead to minor issues like roof leaks or severe consequences such as damage to the building structure, moisture exposure to electrical equipment, and even fire risks. Therefore, waterproofing performance is not just a technical detail but a critical indicator for measuring the reliability and return on investment of a PV power plant.
As a professional supplier of PV mounting systems and fasteners, Suzhou Bilateral Import & Export Co., Ltd. continuously optimizes the waterproofing design and solutions for solar hanger bolts and solar mounting systems based on years of practical experience, ensuring the long-term stability of rooftop PV systems.
2. Why is Waterproofing So Critical in Solar Hanger Bolt Installation?
2.1 Penetration Installation and Waterproofing Challenges
- Hanger bolts are fixed to wooden beams or steel purlins by drilling holes through tiles or metal roofing sheets.
- These holes become potential water ingress points, especially under long-term exposure to wind and rain.
- Waterproofing difficulty varies significantly depending on the roof type:
- Concrete Tiles: Prone to cracking and have uneven edges.
- Metal Tiles: Experience frequent thermal expansion and contraction, testing the durability of waterproofing gaskets.
- Asphalt Shingles: Material can soften or become brittle, requiring reliance on high-performance sealants.
2.2 Typical Consequences of Waterproofing Failure
- Structural Risks: Rotting of wooden beams, corrosion of steel members.
- Energy Loss: Damage to insulation layers, reducing building energy efficiency.
- Safety Hazards: Indoor leaks potentially threaten electrical equipment and personnel safety.
- Increased O&M Costs: Repeated repairs add cost pressure for owners and EPC contractors.
3. Common Waterproofing Designs and Solutions
3.1 EPDM Waterproofing Gasket (Rubber Washer)
- Performance: UV resistant, withstands high and low temperatures (-40°C to 120°C), highly elastic.
- Application: Used with M8/M10/M12 solar hanger bolts to form the first sealing barrier.
- Advantages: Easy installation, low cost, strong applicability.
3.2 Stainless Steel / Aluminum Alloy Waterproofing Washer
- Function: Enhances clamping force, prevents long-term deformation of the EPDM gasket under compression.
- Application: Often used in combination with EPDM to form a “double-layer waterproofing structure.”
- Advantages: Improves long-term durability of the system for 15-20 years.
3.3 Silicone Sealant
- Performance: High fluidity, can fill gaps around the drill hole.
- Applicable Scenarios: Areas with high rainfall and frequent typhoons, such as Southeast Asia, South America.
- Advantages: Serves as an auxiliary waterproofing layer, enhancing overall sealing reliability.
3.4 Integrated Waterproof Solar Hanger Bolt
- Structure: Integrates a waterproof cap and waterproof sleeve.
- Advantages: Simplified installation process, more stable waterproofing performance.
- Application: Suitable for EPC projects requiring high installation efficiency and long-term reliability.
4. Key Points for Waterproof Installation
- Hole Diameter Control: Drill hole diameter should be slightly smaller than the thread diameter to prevent gasket failure.
- Location Selection: For metal tiles, install at the crest of the corrugation to minimize water pooling.
- Torque Control: Bolts must be tightened correctly – neither too loose nor too tight to avoid crushing the washer.
- Gasket Placement: The EPDM gasket must be flush against the roof surface without edges lifting; it must only be assembled on the shank of the solar hanger bolt, not on the threads.
- Secondary Sealing: In extreme climate zones, apply silicone sealant around the outside of the waterproof gasket as an extra measure.
- Installation Training: Ensure the installation team is familiar with construction specifications.
5. Waterproofing Strategies for Different Roof Systems
Concrete Tile Roof
- Recommended Solution: solar hanger bolt + EPDM washer + waterproof cap combination.
- Apply additional sealant on uneven tile surfaces to avoid leaks through micro-gaps.
Metal Tile Roof
- Recommended Solution: Thickened EPDM gasket + stainless steel waterproofing washer.
- Locate bolt penetration points at the crest of the corrugation to avoid water channeling.
Flat Roof / Color Steel Sheet Roof
- Recommended Solution: Solar pitched roof mounting system combined with water drainage design.
- It can be complemented with waterproofing membranes for enhanced sealing performance.
6. Waterproofing Performance Testing and Maintenance
- Water Spray Test: Conduct a 15-minute spray test after installation to check for leaks.
- Annual Inspection: Recommend inspecting EPDM gaskets and sealant annually.
- Replacement Cycle: EPDM typically lasts 10-15 years; replace if aging is detected.
- Long-Term Reliability: Using high-quality solar hanger bolts ensures compatibility with the 25-year design life of PV power plants.
7. Conclusion
Waterproofing design is the cornerstone for the long-term stable operation of solar hanger bolts in rooftop PV systems.
High-quality EPDM gaskets, waterproofing washers, and integrated waterproofing designs are key to ensuring a leak-free system.
Scientific installation practices and regular maintenance significantly reduce operation and maintenance costs.
Waterproofing performance directly impacts the safety, economy, and customer satisfaction of a PV system.
As a professional supplier, Suzhou Bilateral Import & Export Co., Ltd. provides a full range of rooftop PV installation solutions, including:
- Solar Hanger Bolts (with EPDM waterproof gaskets, multiple specifications available, customizable upon request).
- Solar Roof Mounting Systems (compatible with flat roofs, pitched roofs, and various concrete tile, metal tile, and color steel sheet roofs).
- Solar Mounting Accessories (middle-clamps, side-clamps, rails, solar clamps, various stainless steel fasteners (such as screws, nuts, washers, bolts), etc.).
Our products have been widely used in residential, commercial, and large-scale PV power plant projects. Relying on high-quality raw materials and strict quality control, we provide customers with long-term, reliable support and waterproofing assurance.
Contact Information
PHONE/WAHTSAPP: +8613451556833
MAIL: sales@szbilateral.com
