Boulder Retaining Walls Project Overview – Sapphire Valley NC
In late winter 2014 we received a website inquiry from RM outlining concerns about existing structural boulder walls, as well as the desire for a patio and fire circle. We visited the site in spring and found the spacious home, a recent foreclosure purchase, had been built on a blast site high in the NC mountains. The granite harvested from the blasting had been used to construct a pair of massive retaining walls for the upper parking area. Unfortunately, the walls were more than just unattractive, they had been constructed without the skill and care necessary to ensure durability, safety or correct drainage. In one section large stumps and trees were protruding from the wall! In short, the walls were just a few freeze/thaw cycles away from failure; they would have to be reconstructed long before a patio could begin. In addition, the staging was perilous, the shot boulders were enormous, some over 8 tons, and the home’s utilities were buried beneath. To make matters worse RM had just finished the parking area in a mix of asphalt and custom pavers. We explained the various issues to RM and his wife E and immediately addressed costs. The project would easily top $100,000. RM, a successful executive, listened thoughtfully. After negotiations and further site visits we began staging in early May. What followed over the next three months is one of the most technical and dramatic transformations we have ever participated in. And, Yes. R and E did get a gorgeous crab orchard spiral staircase, stone patio and fireplace in the end. The photographs, though representative, fail to capture the magnitude of the site.
Boulder Walls – The Land
The M residence is perched high on a granite outcropping in Jackson County NC. The paved access road is a series of steep, tight switchbacks with other vacation houses nestled below. The existing retaining walls were set without proper footing construction, joint contact and crossing, hearting, or drainage installation. In layman’s terms they violated all basic wall building principles. They also contained stumps, trees and other vegetative material, a big No-No. In addition, the walls were outwardly battered, which gave the menacing sense of inevitable failure seen in the photos. The expansive upper parking area was adequate for staging but required extensive protection and extreme care. The existing walls contained only about two thirds the amount of rock required to complete the project. Finally, all the homes infrastructure, power, phone, septic and drainage lines were buried precariously below the lower wall and would necessitate removal and reconfiguration. In short, the land offered no gimme’s. Even re-vegetation and surface drainage demanded serious consideration.
Boulder Walls – Education
The initial education component focused on thorough site assessment and a detailed explanation of correct walling technique such that R and E could make a comfortable decision regarding the company most qualified for the project. Secondly, we felt a strong need to describe the reconstruction process in a manner that assisted good visualization. The initial demolition was not pretty and a leap of faith was required to see the final product. For this reason we decided to build, “cap” and “pin’ the smaller upper wall first. Although the worst was yet to come this strategy generated some sense of relief and accomplishment. To their credit R and E began investing more heavily in the creative process once this section was completed. Their evolving input, in addition to some fine cooking, was a contributing factor to the success of the project.
From our standpoint the education component was continuous. Until the lower walls were disassembled there was really no way to determine construction access, new wall height and utility routes. The longed-for patio was buried deep in the wall reconstruction process and ultimately required much debate and reconfiguration. The stair construction, a half-turn stairwell comprised of 21 quarried crab orchard treads and elaborate returns, was also a big unknown up until the end.
Boulder Walls – Planning
Much of the initial planning focused on staging difficulties, driveway protection, materials sourcing and handling, safety and weather. Three-quarter-inch plywood and gussets were laid over the entire exposed area of the drive. Large tarpaulins were also brought to help keep the site workable in wet weather – Transylvania county is one of the wettest on the East Coast. A mini-excavator was staged, along with a much larger 32,000lb Link Belt excavator, to minimize traffic across the soft asphalt. Heavy duty 30,000lb-rated chains and custom rigging were purchased, and all unstable rock and inappropriate vegetation was removed early in the process. A major focus of the planning phase was the decision to combine the two lower walls into a one larger wall; this conserved stone and allowed for the construction of safe material and equipment access.
Much of the detailed planning required for the huge lower walls, stone stairs and patio would be a process of discovery, analysis and debate. The best way to ensure this would go smoothly was the teamwork of an expert masonry crew and senior site foreman present at all time.
Boulder Walls – Consolidation
The consolidation component of RM’s project was especially challenging and extensive. As mentioned, two track hoes were staged in an effort to, both minimize driveway damage, and allow two crews to work simultaneously. This strategy worked especially well once the lower walls and stairs were underway. Consolidation extended to task order and site layout. As the upper wall was completed lower wall footings and new utility routes were dug, the lower access road was cut and boulders were staged within easy reach of the big Link Belt excavator. As a way to maximize stone and assist handling, the largest boulders were split with feathers and wedges in traditional masonry fashion. We also worked with the local quarry to allow our masons to pick boulders directly from their “shot” fields. Selecting individual boulders sped up the wall building process and assisted tighter wall construction for the separate patio wall and its enormous “woven” 90 degree corner.
All the while, quality backfill material was imported and compacted in 6” lifts to support the massive suspended patio now underway…. It is worth mentioning that the patio wall footing had to be hammered into the bedrock below the house with a mounted hydraulic hammer.
Once the structural walls and backfill were in place a tremendous amount of finish work remained. Stone stairs, a garden wall, lighting, drainage, site restoration and the 18’ x 24’ crab orchard patio. In addition, propane lines for a raised fire pit were required. Multiple deliveries of quarried flag stone was needed as we were only able to source high quality rock a little at a time. Master masons Franklin Smith and Josh Rigell made the most of it, creating a striking and perfectly constructed patio and landing. V&V site foreman Andy O’Rourke and his crew put the finishing touches on the project by expertly re-grading, matting and hand-seeding the entire site. The project culminated with some thoughtful viewscaping by the V&V tree crew and the installation of a split rail fence above the massive lower wall. Landscaping awaits spring. Huge thanks to all involved!