Farringdon. Listed butterfly roof survey.

The butterfly roof has inward-facing slopes meeting at a central gutter. Its concrete tiles contrast with the natural slate still visible on a neighbouring roof. The survey identifies Welsh slate as the intended replacement, bringing the covering back towards the material described for this listed house rather than retaining the later concrete tiles.

The roofer raises a concern about the weight of the replacement covering, but explicitly says he cannot see bowing during this inspection. That distinction matters: the film does not establish structural deformation or provide a load calculation. Checking the rafters once the covering is removed is part of the proposed sequence, before the renewed roof is built up with underlay, battens and slate.

At the central box gutter, the survey describes lead rolled out in long sections and simply lapped over adjoining sheets. The roofer points out leakage along the gutter and lead that has split over time. A new lining is therefore proposed, rather than relying on another overlap to cover the damaged material.

Movement detailing is a central part of that renewal. Lead expands and contracts with temperature changes; the joints must accommodate that movement instead of leaving the metal to split at a constrained connection. The film calls for expansion joints, but the appropriate section lengths and joint arrangement need to suit this gutter's dimensions and detailing. Replacing the lead alone would not explain how the same vulnerability is to be addressed.

The inspection finds coping joints beginning to break away, moss where moisture sits, and render that has detached from the wall. It also identifies mortar falling from chimney joints. Those observations extend the scope beyond the tiles and gutter: the exposed masonry and its weathering details need to be considered together with the roof renewal.

The proposed approach includes lime repointing to the chimneys, lime render to the walls and lead capping to the parapet. Existing chimney vent bricks are noted positively for helping the chimney breathe. The lead capping is a proposal for this roof, not an assumed requirement for every listed parapet; its suitability and appearance would need to be agreed as part of the heritage repair approach.

Alongside Welsh slate and renewed leadwork, the roofer proposes clay ridge tiles and questions the suitability of the existing roof window. He refers to a conservation or other appropriate window depending on what is required. The intended repair is therefore not simply a like-for-like replacement of everything currently on the roof: the materials and details need to be considered in relation to the listed building.

Before that proposal becomes a specification, the required heritage consents, roof-window choice and treatment of the parapets should be agreed. Scaffold access and the inspection of the exposed rafters would then support the planned renewal. The survey provides a clear account of the visible condition and a direction for repair, without claiming approval, a confirmed structural assessment or a finished result.