Solar Panels on Slate Roofs: What’s Involved

Yes, you can put solar panels on a slate roof. A huge number of London’s Victorian and Edwardian houses have slate roofs, and many have solar. Slate is more brittle than tile, so the fixing method matters: the brackets that hold the panel rails have to come out through the slates without cracking them or letting water in. Done properly, a slate roof is a good place for solar. Done badly, it leaks.

Key points

• Slate roofs can take solar, but slates crack easily, so they need careful handling and the right brackets.

• Brackets are fixed to the rafters, and the slates around each bracket are cut, replaced or fitted with a flashing so water still runs off.

• Older roofs need checking first: the condition of the slates, the nails holding them, the battens and the felt.

• Some older slate-look roofs are fibre cement, which can contain asbestos if fitted before 2000.

• If the roof is near the end of its life, it is usually better to re-roof first and install the solar on the new roof.

• Many slate roofs are in conservation areas, where the planning rules can differ.

How panels are fixed to a slate roof

The panels sit on aluminium rails. The rails are held by brackets, called roof hooks, that are fixed into the rafters underneath. On a tiled roof, the hook passes through the gap between two tiles. Slates lie flatter and tighter, so there is less room, and they crack if they are lifted or bent too far.

The usual approaches are:

• Removing a slate at each bracket position, fixing the bracket to the rafter, and replacing the slate with a flashing or a cut slate that lets the bracket through while keeping water out.

• Using brackets designed for slate, which are thin enough to pass between slates and come with flashings that sit under the course above.

Either way, the brackets go into the rafters, not just the battens, and every penetration is weatherproofed. On a pitched roof we typically use mounting systems from Van der Valk or K2, with fixings suited to the roof covering.

Checking an older slate roof first

Many London slate roofs are original, or were last re-roofed decades ago. Before any panels go on, the survey checks:

• The slates themselves. Cracked, delaminating or slipped slates are common on older roofs.

• Nail sickness. The nails holding slates rust over time, and slates start slipping. A roof with widespread nail sickness will keep shedding slates around the panels.

• Battens and felt. Rotten battens or failed felt underneath mean the roof is near the end of its life.

• The structure. Rafter size and condition decide whether the roof can take the extra load and where the brackets can go.

Our guide to whether your London roof is suitable for solar covers the wider checks.

Natural slate or fibre cement?

Not every slate-look roof is natural slate. Many roofs re-covered in the twentieth century used fibre-cement slates. The HSE says asbestos may be present in any building built or refurbished before 2000, and asbestos cement roofing is one of the places it can be found.

If your roof might have older fibre-cement slates, it needs identifying before anyone cuts or drills them. That affects how the work is done and sometimes whether it’s better to re-roof first. We check this at survey.

When to re-roof first

If the slates or the structure underneath are near the end of their life, installing solar on top only stores up trouble: the panels would have to come off again for the roof to be replaced, which means a second scaffold and extra cost.

In that case it usually makes sense to re-roof first and install the panels straight onto the new roof, with one scaffold and one team. As SPL Roofing we can do both. Our guides to whether you need a new roof before solar and removing solar panels for roof repairs explain the options.

Planning and slate roofs

Slate roofs are common on period houses, and many period houses are in conservation areas. Solar on the roof slope of a house in a conservation area is often still permitted development, but there are exceptions, including Article 4 directions and listed buildings. Our guides to planning permission for solar in London and Article 4 directions explain what applies.

All-black panels tend to sit more quietly on a dark slate roof, which can matter in a conservation area.

Frequently asked questions

Can you put solar panels on a slate roof?

Yes. The brackets are fixed to the rafters and the slates around them are cut, replaced or flashed so the roof stays watertight.

Will solar panels damage my slate roof?

They shouldn’t if they are fitted carefully with suitable brackets and flashings. Slates crack easily, so walking on and lifting them needs care.

Is a slate roof too old for solar?

Not necessarily. But if the slates are slipping, the nails have failed or the battens are rotten, it is usually better to re-roof first.

Do slate roofs contain asbestos?

Natural slate doesn’t. Some fibre-cement slates fitted before 2000 can, so they need identifying before work starts.

Do I need planning permission for solar on a slate roof?

Usually not, but conservation areas, Article 4 directions and listed buildings can change that. We check at survey.

Request a solar and battery quotation. We’ll survey your slate roof, check its condition, and tell you honestly whether to install now or re-roof first.