Solar Panels on Tile Roofs

The most common covering

Tile covers the majority of the housing we work on. Concrete interlocking tile from the 1950s onwards, clay pantile and double Roman across older and regional stock, and plain clay tile on the oldest properties and on anything built to look older.

They are not equivalent. The fixing detail, the labour, the breakage rate and the price all change with the tile.

How the fixing works

The principle is the same across every tile type and it is worth stating plainly, because getting it wrong is the most common defect we find on other people’s installations.

A tile hook is a shaped steel bracket. Its foot bolts into the rafter. Its neck passes out under the tile above and turns up to receive the mounting rail. The tile that sits over the hook has a small amount of material relieved from its underside so that it beds down flat rather than rocking on the steel.

Nothing is drilled through the face of a tile. Nothing is fixed to a batten — a batten is a thin timber for hanging tiles on and has no structural capacity for array loading. The load path runs hook to rafter; the water path runs over the top of the tile as it always did. Separating those two paths is what keeps a tiled roof watertight after an installation.

Tile by tile

Concrete interlocking. The easiest. Large format, robust, regular, with a well-established hook detail and spares available. Old ones become brittle and the surface delaminates, so a 1970s roof yields more breakages than a 1990s one.

Clay pantile and double Roman. The profile is the complication. A hook has to match the tile shape so the relieved tile sits properly over it, and reclaimed pantile varies in size and camber, which makes setting out slower.

Plain clay tile. Small, double-lapped and hand-nailed. Disturbing one disturbs several, breakage is higher, and the labour per fixing is substantially greater. Priced accordingly.

Dry-fix systems. Modern ridges, hips and verges use proprietary dry-fix components rather than mortar. Where the array perimeter approaches them, they are reinstated with their own parts, not bedded in.

Structure and set-out

Fixings land in rafters or truss members, so the array is set out against the actual centres. On trussed roofs those are regular and predictable. On cut roofs and older properties they wander, and rail-based mounting is what absorbs the variation — after the centres have been measured from inside the loft rather than assumed.

Beneath the tiles, membrane type matters. Modern breathable membrane is tolerant but is part of the ventilation strategy. Older bitumen felt tears at a fixing and needs dressing. Pre-war roofs frequently have no membrane at all, which raises the standard for how precisely tiles go back.

Design, access and limitations

Tile roofs allow conventional on-roof mounting with an air gap behind the panels, which keeps them slightly cooler and marginally more productive than an integrated array. In-roof is the alternative where appearance matters: the tile under the array is removed and replaced with a tray system so the panels sit flush.

Bird proofing is worth considering on tile. The gap between panel and tile is an attractive nesting space for pigeons and gulls, and mesh fitted at installation is much cheaper than clearing a colony later.

Honest limitations: an old, brittle covering nearing the end of its life should be replaced before an array goes on it, obsolete tile profiles can be difficult to match, and no tile roof is immune to a poor fixing detail. The method is what makes the difference, not the material.