As architects, we must prioritise structural efficiency in our earliest concept sketches, often before the engineers are appointed. The buildings we build now must be ‘long life, loose fit’ to ensure they can be adapted to future needs. Smaller building grids usually reduce upfront embodied carbon but are sometimes resisted as being less adaptable. In fact, the most common reason for not being able to reuse an existing structural frame is that the floor-to-floor height is too small, not that there are too many columns. With an extra few hundred millimetres on the storey height, a building is much more adaptable and future-proofed to new servicing strategies or local structural changes. We believe that embodied carbon is often better spent on storey height, giving better daylighting and ventilation options, than in a wider column spacing. On one of our larger workplace schemes, we have developed an innovative ‘tree column’ to give smaller structural grid efficiencies while maintaining a wider column spacing. When minimising embodied carbon is a serious goal, innovative designs arise through collaboration.
Facade and structure
Structural efficiency doesn’t end with the building grid. The way the facade is supported or restrained by the primary structure can have a big impact on the structural embodied carbon and the way it’s made affects its aesthetic. So our first concept sketches can set constraints on the facade which affect the structure and we must be mindful of the impact on embodied carbon.
It’s not as simple as a heavy facade needing more structure than a light facade; often, limits on structural deflection are more critical. The diagrams below show four different ways that the facade can interface with the primary structure.
CLT panel used as a backing wall for the ceramic rainscreen at our Teaching and Learning Building for University of Nottingham. This loads the structural frame at the grid lines.