Solar panels on two roofs
of one house in Anerley

Scaffold first, then the trays

With the scaffold up at the back of the house, the first thing onto the flat dormer roof was the mounting: plastic ballast trays set out in rows and loaded with weight before a single panel went near them.

Nothing is screwed or bonded to the roof covering. The weight holds the array down, so the flat roof stays exactly as watertight as it was.

Tilted, not laid flat

The panels clamp onto the trays at an angle. A panel lying flat on a roof faces the sky rather than the sun, holds water and collects dirt; tilted, the rain washes it and it produces more across the year.

The flat roof carries six panels and has its own string, labelled at the cable end as exactly that, so the two roofs never have to be worked out from scratch by whoever services the system next.

The finished flat roof

Two rows on the dormer, with the trays in line and a walkway left between them, so every panel can be reached without stepping on another.

Around the roof windows, not over them

On the tiled slope the rest of the array sits on rails, laid out around the two roof windows of the loft room. The room keeps its daylight, and the panels still take the slope that faces the sun.

A cable route you can inspect

The DC cables come off the roof and down the rendered wall in galvanised steel conduit, clipped in straight runs, turned around the downpipe with proper bends, and into a junction box.

It costs more than loose cable tied to a pipe. It is also the difference between a route an electrician can trace in ten years and one they have to guess at.

Tested before it was switched on

Every cable end in the junction box was marked, and the strings were checked with a voltage tester before the system was connected.