Leaks caused by drilling holes in photovoltaic rooftops are not sudden problems, but rather the result of long-term accumulated risks. All water leakage issues can be traced back to specific construction defects, and the core causes can be divided into four points:

1. The waterproofing layer is directly breached, creating a permanent pathway for water ingress

Drilling holes for mounting brackets directly penetrates the roof’s existing protective layers, such as waterproof coatings and waterproof membranes, completely compromising the building’s original waterproofing system. Unless multi-layered, closed-loop waterproofing reinforcement is carried out, rainwater will continue to seep in through the gaps between the bolts and the holes, creating a permanent pathway for water ingress that is difficult to repair or remedy at a later stage.

2. Failure of anchor bolt seals, with gaps forming due to thermal expansion and contraction

Outdoor environments are subject to extreme temperature fluctuations between day and night and across the seasons, and there is a marked difference in the thermal expansion and contraction coefficients between metal anchor bolts and concrete or mortar roofing. Prolonged and repeated deformation and tension will cause minute gaps to form between the bolts and the holes. Simply applying sealant to the surface is insufficient to seal deep-seated gaps; over time, the seal fails, allowing rainwater to continuously seep into the internal structure.

3. Hasty and slapdash sealing with poor weather resistance, prone to ageing and cracking

To cut costs, most low-cost contractors on the market simply seal holes using ordinary glass sealant or substandard sealants. These materials offer extremely poor resistance to UV radiation, ageing, and extreme temperatures. After years of exposure to the elements—sun, rain and wind—they will begin to chalk, crack and flake off within just 1–2 years, completely losing their waterproofing ability and causing roof leaks.

4. Errors in the planning of drilling locations, resulting in holes being subjected to prolonged waterlogging

Due to a failure to carry out precise layout and positioning during construction, support anchor points were haphazardly drilled at low points in the roof drainage system, in drainage channels and in water-collecting depressions. As a result, the holes were subjected to prolonged waterlogging, with water pressure continuously seeping into the gaps, significantly increasing the likelihood of water ingress. This constitutes an irreversible construction error and is a major cause of frequent leaks in ageing photovoltaic rooftops.

Drilling holes for photovoltaic mounting brackets is not the root cause of water leakage; rather, substandard installation, poor-quality auxiliary materials and the omission of waterproofing procedures are the core issues behind roof leaks. The mounting brackets themselves, once anchored in place, are structurally sound and offer excellent wind resistance. Provided they are combined with standardised waterproofing installation practices, high-quality waterproofing components and specialised sealing materials, they can fully meet the 25-year service life of a photovoltaic power station, eliminating any risk of water ingress throughout its entire lifespan.