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945 GREEN STREET PROJECT

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The comprehensive restoration program formulated and executed for the historic 945 Green Street high-rise apartment tower in San Francisco carries a price tag that might produce a jolt of sticker shock, even for the well-heeled railroad heir who built the steel and concrete palace in the 1920s.

But the current owners—residents of the building’s 12 sprawling apartment units—are getting their money’s worth, says Brian Neumann the project architect who directed the restoration overhaul and the payoff on the investment is considerable. “They let us give them back a fantastic building.”

“They spent a ton of money, out of their own pockets,” said Brian Neumann, the project architect. “There were a couple of huge special assessments for this.”

But, Neumann said, the payoff on the investment is considerable. “They let us give a fantastic building back.”

Neumann, principal with Neumann Sloat Blanco Architects LLP, and Alpha Restoration & Waterproofing collaborated to take on the extensive remediation plan that included repair and restoration, removal of multiple facade coating layers, re-creation of wholly or partly missing decorative elements, and installation of new windows designed to match the original, massive glazing.

The building was designed by noted architects Quandt and Bos and built by railroad heir C. Templeton Crocker who was the grandson of Charles Crocker, one of the “Big Four” who built the Central Pacific Railroad, along with Leland Stanford, Collis Huntington and Mark Hopkins.

Neumann describes the building as elegant but simple in its beauty—steel frame structure, cast-in-place concrete, sprawling single-floor apartment units, and expansive single-frame windows. The elegance derives from Italianate design elements, combined with a few flourishes, such as the decorative cornice hanging high above, the touch of nobility and whimsy with sculptural curiosities, and classical themes with columns and arches.

“It’s typical of San Francisco architects of that time,” Neuman said. “A bit of a mix and match.”

Patchwork Maintenance

The restoration story began four years ago, Neumann says, when he was called in by a representative of the building’s owners—the residents of the 12 units, each of which, spans an entire floor of the 14-story building -- to formulate a scope of work to address problems with the exterior.

“They literally had been maintaining this building for about 80 years,” he said—essentially a band-aid approach.

“They’ve done patches, crack repairs, they’ve been coating it. They’ve never done any kind of real major work on the building.”

The owners knew they lived in a fixer upper, but figured the bill would run in the five-figure neighborhood. Neumann’s analysis quickly scuttled that kind of wishful thinking.

Neumann boarded swing-stage rigging for a close-up condition survey. “When we got up there, I saw a lot of little blisters, everywhere. We would cut one out, and it would peel off, and we found there would be a smell, with puddles of water in places” (under the coating). It was green, indicating the blisters had been there a long time.

Still, Neuman had not heard of any complaints about water intrusion from the residents. Where was the moisture going? It was getting under the coating, into the concrete. With further probing, Neumann saw major spalling was occurring, indicating more than a surface fix was needed. Water had been held back from entering the building interior, apparently by the interior plaster, but had caused damage to the exterior, under multiple layers of elastomeric coatings.

Damage and decay was more clearly evident elsewhere. Water tables could easily be knocked apart. “It was loose and came off in my hands,” Neumann said of the concrete.

Neumann advised the owners of potential dangers and liabilities— “what-ifs,” such as falling concrete crashing through the roof of an adjacent building, or worse. An initial “stopgap” repair program was launched, addressing spalling with removal of weak concrete and fastening of large decorative panels on the upper exterior that had started to disbond.

Window Fix

These weren’t your average windows, but expansive single-glazed elements of approximately 5 by 7 feet in size. Again, some superficial repairs and window replacements had been done over the years, but damage and decay to existing redwood frames was widespread, in addition to degradation of adjacent concrete facade.

A specification was developed for a window-replacement program, based in part on a wind-pressure study on the building. The analysis showed that the heaviest positive and negative pressures occurred on the southeast corner of the building’s mezzanine level, not far from street level, surprisingly. This result was attributed to the building’s location and the tunnel effect produced by other nearby structures. The spec called for resistance up to 6 pounds per square foot.

New windows were custom made by Woodstone Co., using cherry wood. “It takes paint well and is hard and durable,” Neumann said.

“We had them build the biggest window they’d ever made,” Neumann said, matching the appearance of the originals.

Testing, based on the ASTM E -1105 standard, was conducted with a mockup of the window assembly and adjacent wall structure.

The actual design pressures were calculated based on the historical weather data for the local region, topography, design and shape of the building, and immediate surroundings, Neumann said.

Approximately 230 windows were replaced—about 90 percent of the building’s total.

The Main Event

The exterior was stripped of multiple coating layers down to the concrete wall surface, using a chemical coating remover and power washing.

Besides degraded concrete facade, they encountered a range of missing or damaged concrete and metal elements, including decorative panels, capitals, floral sculptures, and cornice sections. For concrete elements, molds were crafted, making use of decorative features that remained intact, to produce new replacement elements.

Scaffold erection proved to be a challenge in its own right, due to the building’s exterior geometry—in particular the overhanging cornice above the 12th floor. Vehicle access to the building’s interior parking spaces remained open during the project, and the contractors erected scaffold systems on top of platforms, creating a bridge over driveway entrances to the parking area. Scaffold planking was covered with plywood and plastic sheeting to prevent damage to grounds or vehicles below from falling debris.

Anticorrision Measures

Subcontractor Concrete Science Inc., a materials and structural engineering specialist firm, was brought in to evaluate corrosion issues and devise protective measures.

Rebar that was exposed due to facade deterioration was cleaned and treated with a three-component epoxy- modified cementious bonding agent/ coating. Anodic zinc “pucks” were attached to rebar in various locations because corrosive action migrates away from the steel rebar and the zinc “pucks” served as the sacrificial corrosion target.

The restoration team also carried out sample testing of penetrating anticorrosion treatments to be applied to the entire concrete exterior, as recommended by Concrete Science Inc. Blind laboratory testing was conducted, using core samples obtained from the building façade to evaluate penetration; a 3-inch depth for this penetration was the criterion set due to the depth of the structural steel.

Repairs

In quantifying the size and scope of concrete repair, concrete spalls and cracks were highlighted with spray paint, detailed on paper, and categorized according to severity and extent. The data was entered into a spreadsheet program as a way to calculate costs, Alpha Restoration and Waterproofing’s project manager Eissa Kishek said. A CAD file showed locations and types of spalls and cracks, locations of sacrificial anodes, and type of repair measures taken.

For concrete repairs, Alpha Restoration employed a number of materials, some incorporating anticorrosion functionality. Choice of material hinged on depth of spalls or cracks, surface alignment (horizontal or vertical/ overhead), and relative importance of structural strength, flexibility, and other performance properties.

In addition to application of the penetrating anticorrosive treatment to the building façade, the restoration team applied a primer followed by application of acrylic elastomeric coatings recommended for use on cementious substrates subject to cracking and dynamic movement, according to product literature. A “buttery white” topcoat color was chosen, Neumann said.

Re-creating Buried, Lost Treasures

In addition to restoring or rebuilding decorative concrete panels and elements and sheet-metal decorative cornice elements, the restoration team was given the assignment of essentially designing and reconstructing an architectural feature that had been obscured in a remodeling that took place several decades ago on street level—a onetime service entrance and doorman’s station that was turned into a breezeway.

Behind a plaster wall in the passageway, the restoration team found decorative panels and the remnants of a fountain element. Neumann Sloat Blanco designed new architectural elements to reconstruct a lion’s-head fountain and adjacent decorative treatments, including two massive GFRC rosette pieces for installation on the breezeway ceiling. The architects drew from the building’s existing decorative themes in designing these elements.

“They won’t even know it’s not original,” Kishek said of building residents and visitors who encounter these new features.

Also added were new light fixtures, again designed to blend with the building’s architecture, and arches built into the facade above the breezeway entrance, serving as a continuum of the building’s existing street-level arches.

A new doorman’s station structure was added, also in a design in keeping with the building’s style, to replace an original wood-framed enclosure.

An aesthetic detail added to ground- level decorative concrete panels was the application of a glaze to flat portions of the surface, producing a shadow effect and adding “pop” to the sculpted relief of the panels.

Complex Recipe for an Exquisit Edifice

Located atop San Francisco’s breathtaking Russian Hill in the Russian Hill-Macondray Lane Historic District, 945 Green Street can reclaim its rightful status as a carefully preserved resident alongside prominent neighbors such as the Eichler Summit next door.

From an aesthetic and design standpoint, Kishek said he’s heard the building described as resembling a “wedding cake.”

That may be a matter for the eye of the beholder. In any event, comprehensive recipe, ingredients and process components were needed to bring back the substance and flavor of this appealing menu item on the San Francisco skyline.

About the Author

Joe Maty is a Contributing Staff Writer.

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