Our practice is focused on restoring buildings’ “skin” and “skeleton”—the exterior envelope and underlying structure. But sometimes our work takes us inside the envelope. One example is our restoration of an interior mural at the Dr. Sun Yat Sen Intermediate School (I.S. 131).

SUPERSTRUCTURES was engaged to provide long-term solutions to the deterioration of the mural, Timeless Spirit (Seong Moy, 1984), located in the building’s lobby. The abstract, geometric composition is constructed of 12″ square tiles crafted from white earthenware with bright, painterly glazes. The tiles are set in grout with hand-tight, flush joints. Our investigation was initiated in response to tiles that had fallen off the wall, in addition to numerous cracks and spalls in the existing tile.

The school’s lobby is used for various community activities, reportedly even as a gymnasium space, so the mural receives frequent wear and distress. As part of a previous repair campaign conducted by others, approximately eight tiles were replaced or re-set, and the remainder were treated in-place. Epoxy injection was used along the seams of several tiles to provide additional stability.

We observed that the reach of the epoxy from the previous repair was limited, often only reattaching the tile edges. Large voids still existed behind many of the tiles where they had never been properly set in a grout bed.

We performed a visual and hands-on inspection of the wall via vertical lift, sounding each tile with a rubber mallet to determine their adhesion to the backup wall. Representative areas were subjected to pull tests. Locations of spalls, cracks, detachment, and hollow areas were documented.

We developed various options for the school to provide long-term stability for the mural, from installing a protective plexiglass cover, to drilling and injecting grout directly into the voids, to removing and resetting all tiles on a panel system.

When testing revealed that the tiles were too fragile to be removed from the wall without damage, we worked with the team at RLA Conservation LLC to find the best materials for in-place grout injection.

In contrast to the previous epoxy repairs, the conservators drilled strategic pilot holes into the tile face to inject grout directly into the voids. Re-sounding the tiles with a mallet after the injection verified that this method was a resounding success.

The conservation team meticulously filled, color-matched, and in-painted each of the pilot holes. The final step to fully restore the mural will be the fabrication of remaining replica tiles.

Watch this space for future posts on our work “inside the envelope.”