How it is built
Stainless steel cables run vertically between anchors at the balcony floor or parapet and the soffit above. Each cable passes through a tensioner, and each is tightened individually to a specified tension.
The anchors are the part that matters. They land in the floor slab and the soffit — on most balconies the soundest structure available — and they have to be fixed into solid concrete rather than screed or repaired render. We check this at survey, because on older Mumbai balconies the parapet top and slab edge have often been made good more than once.
Why vertical is the default
It anchors into better structure
A vertical run has the slab below and the soffit above. A horizontal run relies on the side walls or jambs, which on a balcony may be masonry rather than concrete and may be shared with a neighbour.
Nothing to climb
This is the safety argument that decides it in most family homes. Closely spaced horizontal cables can function as a ladder for a determined toddler. Vertical cables offer no foothold at all.
Where horizontals are preferred for appearance, we say this plainly rather than leave it for later. See horizontal wire grills for when they are the right call.
It reads as less visible
Against a city skyline of vertical buildings and edges, vertical lines disappear more readily than horizontal ones. The difference is subtle but real from inside the room.
Spacing and tension
Spacing follows safety standards — close enough that a small child or a pet cannot pass through. Tension is specified so the cable is taut with negligible deflection under load, and each cable is individually adjustable.
Annual checking is worth the few minutes it takes. A cable that has gone slightly slack is re-tensioned in seconds; one left for years puts extra load on its neighbours.
Materials
Marine-grade stainless for cable, anchors, tensioners and end caps. This is not an upgrade in coastal Mumbai — a lower grade will pit within a couple of monsoons and leave rust staining down the parapet.
Where it suits
Balcony edges of any depth, window openings above ground floor, terrace parapets and internal void edges. For the residential decision in more detail, see invisible grills for balconies in Mumbai, or the full invisible grill range for the other five systems — including cable mesh, which is the choice where a pet climbs.