The last blog post showed the formwork for the Trombe wall nearing completion. Now the stair has been fully revealed and is being left to cure for 28 days.
The Trombe wall was poured using a crane and bucket. It was then left over the weekend and struck on the Monday morning. Positional keys and reinforcing connections were left to build the steps from, ensuring the board-marked finish ran consistently up the risers.
The same 50% GGBS mix has been used to minimise the environmental impact of this carefully positioned lump of thermal mass, providing the building’s low tech solar powered ‘night storage heater’.
Each formwork board matches the exact dimension of the external cladding boards, providing a visual through-line between the external lightweight cladding and the heavyweight internal in-situ stair.
Each step was floated and trowelled with a small bull-nose to minimise risk of scuffing or crumbling. The radii of the bull-noses are precisely 10 times smaller than the radii of the wall itself.