West facade showing typical cracks in the stone wall telegraphing though the stucco surface (above) and the chased cracks (below right).
This week Federal Masonry Restoration has begun the assessment phase of the masonry repair project under the watchful eye of Aeon Preservation Services.
Craftsmen have “chased” (carefully removed loose material) persistent cracks in the exterior wall system which have “telegraphed” through the stucco exterior surface, to reveal the source of the problem. Since these are very thick (2′-3′) mostly stone walls the centers are often filled with rubble and cemented together with lime based mortar. Inside the walls the mortar has powdered in some areas and we have even found whole oyster shells as part of the fill.
The discovery process involves “sounding” or tapping lightly upon the entire wall surface with a hammer to discover hollow sounding areas which indicate loose masonry and or that the stucco has separated from the wall surface.
In removing the layers of stucco on the surface, we have found numerous campaigns of repair beginning with the original lime/oyster shell mortar, and later Portland cement based mortars, and even some ready mix concrete. It appears that the top layer of stucco applied during the 1980 restoration contained a much softer Portland cement based plaster mix, though with none of the oyster shell particulates.
The good news is that the cracks so far are all localized and are not as a result of foundation subsidence (from poor construction or sinking soils), so the repairs are quite typical – grouting with a lime based mortar in several lifts to fill all of the voids and bring the “chased” cracks back to the adjacent intact stucco surface.
We’ll talk about the chimney conditions in another post as they are constructed of brick masonry and were a concern as a result of the earthquake a few years ago.
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