Solar Panels on 1920 to 1965 Homes

What characterises housing of this period

Between the wars and into the early post-war years, Britain built at scale: semi-detached suburbs, council estates, ribbon development along arterial roads. The construction is broadly consistent — cavity walls, a cut timber roof, clay tile early on and concrete tile from the 1950s — but the roof shapes are not. Hips, gables, bays, catslides and later extensions all turn up, sometimes on the same street.

For solar, this is generally good territory. Pitches tend to be conventional, the timber is sawn to reasonable sections, and the roofs are high enough to escape most ground-level shading. The complications are about shape rather than substance.

Hipped roofs and usable area

The defining constraint of the period. A hipped roof presents a trapezoid, not a rectangle, and an array laid onto it loses panels at both top corners. Keeping the required clearance from the hip lines and the ridge costs more area again.

The practical consequence is that a house which looks like it should take fourteen panels takes ten, and those ten may split across two slopes. Where the hips face east and west, splitting the array deliberately across both is often a better outcome than crowding one face.

Chimneys and shading

Interwar houses were built with fireplaces, and the stacks are frequently central or on the party wall. A central stack casts a moving shadow across one slope for part of the day and the other slope later — a genuine loss, not a theoretical one, and it lands on the middle of the roof rather than the edge.

We assess this properly at survey rather than assuming an optimiser will absorb it. Sometimes the answer is per-panel electronics, sometimes it is a layout that simply leaves the shaded band empty.

Covering condition

Clay tiles of the 1920s and 30s are usually sound if the nibs and fixings are. Early concrete tiles are the ones to watch: fifty to seventy years of frost gets into the surface, and delaminated or crazed tiles break when handled. Many roofs of this age were built without sarking felt, or with bitumen felt that has since perished into strips.

Where a covering is near the end of its life, re-covering before installation is almost always the cheaper sequence. Putting an array onto a roof that needs stripping in five years means paying for removal and refit as well.

Structure, access and electrics

These are cut roofs, not trusses, so members are individual and spacing varies. Loft hatches are small and eaves headroom is tight, which affects how DC cable is routed and where an inverter can sensibly be sited and later serviced.

On the electrical side, the board is often a 1990s or 2000s replacement that is serviceable but full. The bigger question is the main fuse and the meter position, particularly where storage and vehicle charging are planned. Generation up to 16A per phase — around 3.68kW single phase — is notified under G98 after commissioning; anything above that is a G99 application that must be approved before work starts.

Limitations

Bay windows and porch roofs are not usable. Rear extensions frequently sit at a shallower pitch or a different orientation and need assessing on their own terms. And a hipped roof with a central stack and mature trees to the south will produce a modest system — worth having, but worth being honest about first.