Vertical purlins or curved battens are made from 35mm x 25mm tile battens, kerfed and steamed at the approximate radius of the Nissen ribs.
Detail around window, showing draught proofing (extruded foam filler) and typical state of wooden purlins. Inner cladding on the left is new and on the right very rusty, though still solid enough to be used.
Detail of fillets intended to keep the profile of the insulation so that it sheds water. The SuperQuilt insulation claims to be watertight or moisture proof – it does not require a separate membrane. All the galvanised nails visible in this picture were taped over before the outer cladding was restored.
70 years of rust
The rust was removed using a vacuum cleaner – filling the dust bag. Rust is particularly heavy.
The window roof extensions with raised slightly to allow for the insulation layer including the requisite air gap.
A 1inch air gap is maintained between the outer cladding and the “SuperQuilt” insulation.
Details of the finishing: The insulation is taped to the window structure to prevent draughts. Awkwardly shaped roof angles are finished with hand beaten lead.