St Dunstan-in-the-East, City of London

Reinstatement of Listed Stonework

The ruin of the Grade I listed church, situated in the heart of the City, has been converted into a public garden. The skeleton of the original nave and chapels, still containing their traceried windows, have been consolidated and are now covered with trees, climbers and overgrown foliage.

In late 2016 London Stone Conservation carried out a conservation and repair program for the City of London Corporation to consolidate the decayed stonework and historic mortar to the chapel and west end of the nave. The works were carried out in two phases, with the first including a survey, make safe and the removal of at risk material. The second phase was carried out following the successful application for buildings consent and involved the reinstatement of the missing stonework and stabilisation of the historic fabric.

The main Portland stone arch had suffered severe structural failures, most likely due to fire and impact damage when the church was hit during the Blitz. The stonework had shattered, causing multi-plane cracks, breaking the stone into individual fragments and undermining the integrity of the structure. Previous attempts at repair were holding the arch together but these in turn had begun to deteriorate. Each individual section of stone was carefully removed, with the condition, location and alignment recorded. This process was continued until a solid stone surface was reached, to provide a secure base for consolidation and reinstatement. The salvaged stone was removed from site and safely stored at the London Stone Conservation workshops before the second phase of works could begin. Each piece of stone was reinstalled to it its original position using austenitic grade stainless steel dowels set in epoxy resin. Friable stonework was consolidated using pigmented dispersed hydrated lime. Voids and delaminations were grouted using a weak lime and pozzolan mix and all water traps and valleys capped with a colour matched lime mortar.

The rendered window reveals to the chapel had also suffered detachment, allowing moisture to penetrate between the layers, causing further separation from the substrate and hollow areas. Following assessment of the damage and precarious condition of the Grade I listed fabric, it was decided that the most appropriate method for repair was to restrain the render in its current position. This involved using bespoke stainless steel fixings with a mesh head, used to spread the load and provide a key for the subsequent application of mortar. This was recessed a few millimetres below the surface, with the restraint carefully drilled through the render layers back into the substrate. The render was secured in pre-designated areas, so as not to apply additional stresses on the weak mortar or historic masonry substrate. Careful analysis of the original mortar, allowed for the use of a range of lime mortars and grouts to match the characteristics of the existing materials. A non-hydraulic lime and pozzolan grout was used to fill the hollows and fractures with the surface cracks and fixing holes made good with a variegated colour matched lime putty and aggregate mix. The reveals were finished with a casein bound pigmented limewash to further protect the historic fabric.