How do I install solar panels on a slate roof?

A solar installation consists of photovoltaic solar panels fixed on metal rails. The metal rails of the solar installation are usually fixed in the roof joinery using hooks. These hooks pass through the overlap between two consecutive rows of roofing elements. The shape and dimensions of the hooks are chosen according to the batten thickness and the shape and dimensions of the slates. Different types of hooks are available on the market. The hooks can also be made to measure according to site specifications.

Under no circumstances should the hooks of the solar installation be supported on the slates themselves. The load from the solar installation must be transferred directly to the underlying roof structure via the hooks. The hooks must therefore be sufficiently rigid to absorb the loads transmitted by the solar installation itself as well as any additional snow load and/or wind load without being subject to excessive deformations which could cause them to come into contact with neighbouring roofing elements. It must always be checked whether the stability of the roof structure is sufficient to support the additional weight of the solar installation.

Attaching the hooks to the underlying roof structure can be done in several ways:

The solution of fixing the hook in an intermediate element (B and C) is more labour-intensive than fixing it directly to the roof timbering (A), but has the advantage that the hook can be freely positioned, independently of the roof timbering and that the load of the solar installation is absorbed by several consecutive rafters.

Whereas with roof tiles it is easier to make an adjustment (partial sawing out) to allow the passage of the hook, slates are too flat and thin to allow the passage of a hook.

The placement of hooks is suggested in the images below:

Source: TV 263 Mounting solar panels on pitched roofs (wtcb)