Balcony with a wall of lit arched niches and a round daybed

A circular piece with a woven synthetic fibre base, a mattress and back cushions. Before buying, measure the diameter against the balcony width including circulation: a metre-and-a-half daybed on a two-metre balcony leaves half a metre to pass, which is exactly the uncomfortable minimum. And check a replacement mattress exists, because it's the first thing to fail and usually outlasted by the frame.

A small-diameter fitting, the kind sold in packs and recessed into the top edge of a recess. What you're buying here is the complete pack from one batch: in a grid, a point at a different temperature shows instantly. Check they can all run off a single dimmable driver, because switching them in groups breaks the pattern every time only part of it is used.

A slotted aluminium or flexible PVC profile with a diffuser, bent to follow a curved edge. It's the part that lets a strip follow a curve without reading as dots: stuck straight onto the edge, the line shows lamp by lamp and the curve loses the continuity that justified it. Check the minimum bend radius on the datasheet before buying, because it varies considerably between models.

Outdoor covers with a geometric pattern in a dark tone, to break up an entirely undyed base. In a night-time scene the scale of the pattern matters more than the colour: a fine print disappears at two metres and reads as a grey smudge, while a large high-contrast motif still registers in the little light there is. Buy two matching rather than four different ones.

Fibre cement or moisture-resistant plasterboard, for building the lining wall the niches are cut into. On a balcony, even a covered one, choose cement board over green plasterboard: it takes ambient damp without bowing and accepts a render finish just like a wall. Buy one board extra for the arch cutting trials, which rarely come out right first time.

A profile that bends cold to follow a curved edge, which is what lets you finish a slatted ceiling cut to a curve without mitring every piece. It’s usually polymer or thin laminated wood. Before buying, check the minimum radius it takes: below that radius it doesn’t bend, it snaps, and there’s no finding out once it’s cut to size.