Because there is no frame to hinge from, and the load path suits it.

A pivot carries the door on a point at top and bottom.

Weight goes down into the floor rather than sideways into a jamb.

A hinged door's weight tries to twist its fixings.

Large heavy glass doors are almost always pivoted.

Hinged glass doors exist but suit lighter panes and specific situations.

It is how far the pivot axis sits from the door edge, and it changes the swing.

A centre pivot lets the door swing both ways.

Leading and trailing edges then project equally.

An offset pivot behaves more like a conventional door.

Changing it afterwards means altering the floor and the glass.

It is a design decision rather than a hardware preference.

A correctly positioned, drained recess formed at construction.

Bottom pivots and floor springs both sit below floor level.

Retrofitting into a finished floor means cutting it.

Where the slab is structural or contains heating that may be impossible.

Position has to be accurate relative to the finished opening.

It is the constraint projects most often underestimate.

Yes, using hinges that clamp the pane between plates.

They work like patch fittings and follow the same rules.

Gaskets keep metal off the glass throughout.

Clamping torque is specified rather than judged.

Glass thickness has to match the fitting's range.

They suit lighter doors and situations where a floor recess is not available.

Only if the pivot provides adjustment, which is worth checking before buying.

A glass door will settle over time.

Without adjustment there is nothing to correct alignment with.

Vertical adjustment sets the gap at the threshold.

Lateral adjustment corrects the door meeting its keep.

Retrofitting an adjustable pivot later means disturbing the floor recess again.

From the glass area and thickness, and it is heavier than people expect.

Toughened glass is dense and full-height doors are large.

Hardware capacity is published as a maximum weight.

Door width also matters because it increases leverage on the pivot.

Manufacturers publish maximum width alongside maximum weight.

Both limits have to be satisfied rather than just the weight figure.

Wear in the pivot bearing, which shows as the door dropping or binding.

A dropped door catches the floor or stops meeting its keep.

Grit in the floor socket accelerates wear.

Sealed and dust-excluded designs last considerably longer.

Adjustment corrects early symptoms rather than worn bearings.

Replacing a bottom pivot generally means unloading the glass, which needs proper lifting equipment.