Kolkata Project Courtyard Tensile Shade

An open courtyard ringed by a building is usable space going to waste if it bakes in the sun and floods in the monsoon. The brief for a shade over it is to cover the whole area, keep the floor as clear as possible, and drain cleanly without dumping water into the surrounding arcades — all while working inside an occupied building with limited access.

Ekra Decor delivered the structure as a turnkey job: survey and setting-out within the courtyard, 3D form-finding and structural design, fabrication of the galvanised steel mast and the membrane, and installation and tensioning, over about 1,115 m² in roughly two months.

A centre-mast cone puts all the vertical load into one point and all the horizontal pull into a ring of perimeter anchors. The membrane is form-found so it hangs in a steep radial double curvature — taut in every direction, stable under wind uplift, and steep enough to shed a Kolkata monsoon straight off its slope.

The single mast carries a large compression force, so its foundation is a substantial pad or pile designed for that plus the overturning from asymmetric wind; the perimeter anchors are designed for uplift and tied into the surrounding building’s structure. Ekra Decor designs the steelwork to IS 800 and takes wind and rain actions to the applicable Indian codes. Because Kolkata is warm, humid and within reach of cyclone-season weather, the steel is hot-dip galvanised and the wind case is taken seriously rather than to a lighter inland figure.

The mast, the tension ring and the perimeter fittings are fabricated and hot-dip galvanised in the workshop, and the cone is cut as radial panels and welded into a single piece off-site. The central foundation is cast within the courtyard.

Erection is quick once the mast is up: the cone is spread out across the courtyard floor, lifted to the mast head, and tensioned down to the perimeter anchors until the peak pulls up true. Working inside an occupied building, access and lifting were the constraints, and the shade was completed in about two months.

The building gained a shaded, rain-protected courtyard with an almost clear floor and a striking single peak overhead — usable space recovered from what the weather had made marginal. The cone needs only periodic cleaning and a check of the mast and cable tensions.

Ekra Decor builds conical and centre-mast courtyard shades for commercial and institutional buildings. See more finished work on the projects page, or read about tensile structures in Kolkata.