Atrium Roofs & Interior Tensile Ceilings

Most tensile work is outdoors, where wind uplift governs everything and the roof’s job is to keep weather out. An atrium roof or an interior tensile ceiling inverts almost all of that. There is no wind. The load case is quiet. And in exchange, three things that barely register on an outdoor canopy become the whole design: fire, light and sound.

That is why this work is quoted and engineered differently, and why a contractor who only builds car park shades is the wrong choice for a mall courtyard. A membrane over occupied floor inside a building sits under that building’s fire strategy, in front of its lighting design, and above its acoustic environment — and it usually has to be installed through a finished, operating building without damaging any of it.

Ekra Decor has done this at Vasant Square Mall, on a 20,000 sq ft atrium courtyard in Lucknow, as an atrium skylight in Guwahati, as a faceted ceiling in Bahadurgarh and as an interior office-floor ceiling in Noida. For the underlying technical background, see the tensile structure guide.

Also a 686 m² commercial structure in Lucknow. See all courtyard and atrium projects →

• Diffuse light instead of hot spots. Glass transmits a directional beam — bright patches that track across the floor, glare on shopfronts and screens, and a space that needs blinds. A translucent membrane scatters the same daylight into an even wash across the whole floor.
• Daylight without the solar gain of clear glazing. A membrane can be specified to pass useful light while transmitting far less solar heat than clear glass, which shows up directly in the cooling load of a large atrium. The specific transmission and shading figures depend on the membrane specified and belong in the project’s energy calculation, not on a web page.
• Far lighter, so the existing structure may cope. A membrane roof weighs a fraction of a glazed one. On a retrofit over an existing courtyard that is often the deciding factor, because the existing frame and foundations may take a membrane where they would need strengthening for glass.
• Bigger spans, fewer members. Less structure in the air means less of the daylight blocked by the thing holding the roof up.
• ETFE where the space should read as open sky. Very high light transmission for atria that should not feel roofed at all. ETFE film →
• Nothing falls out of it. No pane to fail over occupied floor — a point building managers raise more often than architects do.

• The membrane still needs prestress. Tension is what keeps the surface taut and wrinkle-free and stops it drumming. A slack interior ceiling looks worse than a slack outdoor one, because people are close enough to see it.
• Load goes into an existing building. On a retrofit the tension has to be taken by something — an existing frame, slab edge or new steel. Whether the host structure can take it is checked before the geometry is fixed, and it sometimes changes the design.
• An atrium roof is still a roof. Roofing a courtyard means rain, falls, gutters, outlets and an overflow route, and in a high-rainfall city like Guwahati that capacity is the governing detail rather than an afterthought.
• Hang nothing off it without asking. Lights, speakers, signage and decorations get added to interior ceilings later. Any of that must be designed in or supported independently — a membrane is not a fixing point.
• Access for cleaning is a design decision. A ceiling fifteen metres above a mall floor has to be reachable. How it will be cleaned, inspected and re-tensioned is settled at design stage; retrofitting access to a finished atrium is expensive and disruptive.
• Coordination with services. Lighting, sprinklers, smoke detection, HVAC and signage all occupy the same volume. The membrane geometry is coordinated against them rather than drawn first.
• Handover pack. As-built drawings, calculations, structural stability certificate, membrane mill and fire certificates, and an O&M manual including the access method.