Semi-frameless and post & handrail are the value options — their posts carry the structural load, so both use 10mm toughened glass, which keeps the cost per metre down. Spigot and channel systems put the load through the glass itself and need thicker laminated panes at height, which is what moves them up the price scale. For most residential decking and patio projects, semi-frameless is the starting point.
Both give you glass-led looks without posts. The spigot system holds each pane on two discreet floor-mounted clamps — a frameless appearance with small fixings visible at the base. The channel system sets the glass into a continuous base channel with nothing else on show at all — the only true frameless glass balustrade. Channel is the more premium route; spigot gets you most of the look for less.
All four work on decking with adequate structure beneath the fixing points. Semi-frameless is the most popular for value and forgiving installation; spigot suits contemporary decks where minimal hardware matters; the channel system is the premium pick where the deck is all about the view. If the deck includes steps, post & handrail handles the staircase run best.
Post & handrail — building regulations require a continuous graspable handrail on staircases, and it's the system built around one. The other systems can serve the level areas either side of the stairs, with post & handrail on the flight itself.
Not always. Under BS 6180:2011, a barrier protecting a drop over 600mm should have a handrail unless toughened laminated glass that stays in place if a panel fails is used — which is exactly how the spigot (21.5mm) and channel systems achieve the no-rail look at height. On stairs a handrail is always required. Each system's page covers its own glass rules in detail.