Solar Panels on Slate Roofs

Why slate needs more care

Slate is thin, brittle and fixed with nails rather than hung on a nib. Anchors have to be placed carefully and the slate dressed or replaced around them. A rushed job on slate shows up as cracked slates and, eventually, water ingress.

The Portsmouth context

Much of the older housing here is dense Victorian terraces, interwar semis, and post-war housing across Portsea Island, with slate and clay tile on the older terraces, concrete tile on later housing. Portsmouth is unusually densely built, so shading from neighbouring roofs is common and coastal wind loading affects the mounting specification.

Fixing detail

Anchors fix to the rafters, with the slate above dressed over the bracket or replaced with a lead soaker. Done properly there is no reliance on sealant to keep the water out.

Age and condition

Old slate can be sound for decades more or can be at the end of its life with failing nails. A survey should include a genuine assessment of that, because it changes the sequencing of the whole job.