Lead was the traditional answer for a box gutter and, dressed properly, it is still a beautiful material. The trouble is that a long box gutter run has to be joined every 1.5 to 2 metres, and every one of those joints becomes a potential failure point after twenty years of thermal movement. Add the theft risk that London has never quite shaken, and the maintenance cost of the material starts to look very different on paper.
GRP fibreglass is laid over the timber deck as a single continuous laminate, with no joints. Nothing to steal, nothing to fatigue, no re-dressing every decade. It carries a 25 year manufacturer warranty and is inert to the pollutants a London roof deals with. For flashings and abutment detail, lead is still the right answer. For a long concealed gutter, the honest answer is GRP.
The reclaimed slate is a different conversation. That is a match, not a specification. We hand-sourced the stock, laid it to the original coursing, and the finished roof reads as one continuous piece of work, not a patch.
London · 2026
