Patching and repairs to the historic cast stone and stucco facade of the Huntington Gallery were performed using proprietary repair mortars and rendering compounds.
The exterior facade is composed of both cast stone and natural limestone decorative elements. Here the typical deterioration of the cast stone due to iron jacking is evident. Since these brackets are located just under the parapet at the cornice, they are subjected to a higher rate of moisture saturation over time. Consequently the interior steel reinforcement failed and pushed the cement matrix apart to relieve stress.
Various attempts at repairs were made to the cast stone portions of the facade over the years. In each variation, grey Portland cement was used and then coated over with paint.
Our restoration process was designed to eliminate this dependence on the repeated application of coatings to hide previous repairs. Once all coatings were removed, we were able to get an accurate assessment of what needed to be done to restore the exterior surfaces to a stable and maintainable condition.
Once interior issues such as reinforcing steel and patching were resolved, we utilized the same repair mortar (including the same custom color formula) to coat all cast stone elements on the building. In addition to providing a pleasing and uniform appearance, we were able to impart a stable surface which, when treated with a penetrating water repellent, provided a durable and long-lasting veneer to the structure.
There were numerous decorative elements, such as this balustrade on the south elevation, that had undergone many years of similar repair philosophy.
As with so many contemporaneous balusters, this one failed because of the iron jacking due to the central mild-steel reinforcing rod.
Here the balustrade and the tasteful excessiveness of the period have been fully restored.
Many decorative elements on the building facade were made of limestone and had undergone a different decay mechanism. Since there were no internal mild steel reinforcing elements, that source of damage could be eliminated as a cause for the deterioration of the stone. The natural water-soluble components of the limestone, however, were adequate to provide a means for the deterioration over time of the limestone decorative elements. Some limestone's can be very durable and resistant to the weathering effects of moisture, but this particular stone was not so fortunate.
Knowledge of sedimentary limestone formation patterns would have helped in the original fabrication of this egg and dart horizontal course. The delamination of the outer layers is evident in this image and could have been mitigated if not eliminated by re-orienting the block of stone prior to carving by 90 degrees to make the sedimentary layers more horizontal in orientation, and therefore less likely to delaminate like the layers of an onion.
In many locations the limestone had uniformly delaminated leaving a regular loss of surface.
Evidence of former attempts at repairs was widespread, and the ineffectiveness of the solutions obvious, as whole layers of stone could be removed with finger pressure.
By using standard mold-making techniques we were able to fabricate new matching curved corner egg and dart units using a proprietary repair mortar color matched to the original cleaned stone.
This corner areas was completely removed to install new structural upgrades and then re-created using newly fabricated and salvaged components.
Another common problem we face on buildings of this period is the use of dissimilar materials, in this case cast-in-place concrete and cast iron balustrades. Here the damage wrought by the rusting iron components of the railing can be observed.
We have a standard response to issues of this nature when dealing with historic structures. We remove the ferrous components embedded in the concrete or cast stone (anchors/supports) and replace them with stainless steel. Here we are welding these new anchors to the base of the original cast iron railing.
Once the replacement and repairs are complete, the adjacent concrete and cast stone patching can be completed. Repair of any drains and application of an elastomeric waterproof coating to the horizontal surfaces of the balcony will complete the comprehensive repair program.
Final details included the rendering of all cast stone surfaces and the re-patination of metallic elements, including these zinc-coated urns.
This restoration cycle in the ongoing history of the structure will hopefully make it possible for a duty cycle of at least 30-40 years before serious attention is paid to further exterior concerns.
The main house at the Huntington Gallery and Museum stands as a testament to the idea of an institution as repository of our cultural and creative history.