Deck Lighting in Madeira, OH

The standard way to light a deck is to run the cable inside the frame, drilled through the joists before the boards go down. On the houses in Madeira (ZIP 45243) where the deck sits over heated space, that is the one method not available, because the structure under those boards is a roof.

A roof works by having an unbroken waterproof layer across it. Everything above that layer is a wearing surface and everything below it is the living room of the people inside, and the only reason it stays dry is that nothing goes through. A hole drilled for a cable is a hole through a roof. So is a fitting recessed into the deck surface, which is why in-floor lights come off the list here before anything else is discussed.

The run goes up instead. Cable travels in the guard: through the posts and along the underside of the rail, above the membrane the whole way, which puts it exactly where the fittings that matter want to be anyway. Post caps and under-rail work normally. The stair, where there is one, takes its risers as usual, because a flight standing on its own bearing is not part of the roof. What changes is the floor plane, and the floor plane is the part of a lighting scheme with least to lose.

The transformer and its supply follow the same rule. It mounts on a wall or on the guard frame, never on the deck surface, and the cable reaches it without crossing the membrane at any point. All of that is settled while the build-up is being drawn, which is the moment somebody is already thinking hard about what does and does not pass through.