So we retained every piece of original Elm rafter we could, re-jigging some of their positions. One rear corner of the wall plate and a principal rafter needed new timber splicing in, due to a leak in the old corrugated tin. Also my mind turned to planning the 'eye brow' window. A curved glue-lam beam was required with a rebate to accept the window frame. Strong enough to carry the roof, so four thicknesses of 25mm engineering ply was glued together and machined out in the workshop.last time we made this type of element was in a marquee on St Margaret's bay for the Prince of Wales's Institute of Architecture.