For on roof PV systems, the array fixing brackets should not affect the weather tightness of the
roof they are fitted to. For example, systems attached to tile roofs should be designed and installed
such that the fixing brackets do not displace the tiles and cause gaps more than naturally occurs
between the tiles. Fixing methods must not subject roof coverings to imposed loads which may
degrade their primary purpose of maintaining weather-tightness.
It is good practice to notch roof tiles when fixing roof brackets to beams.
Tiles or slates removed for fixing a mounting bracket should be re-attached to include a mechanical fixing.
Historically, some mounting systems on slate or tile roofs have relied on a simple “through bolt”
approach. However, this fixing method has the potential for the fixing bolts or sealing washer
cracking the slates/tiles beneath them. It can also present difficulties with ensuring the long term
weather tightness and durability of the roof penetration.
Through bolts shall only be used on tile or slate roofs where the following requirements are met:
1. The bolt or flashing shall not transfer any load on the slates / tiles beneath
2. The system shall not rely on silicone or other mastic sealant to provide a weather-tight seal
3. The system must durably seal every layer of roof covering that is perforated by the bolt system
4. The system shall not rely on a sealing washer or plate that presses down on the slate/tile to
ensure a weather tight seal
5. The bolt fixings shall not be into battens