Landscape Architect Articles

Waterfall Paradise on the 13th Floor07-07-11 | News

Waterfall Paradise on the 13th Floor
By Erin R. Spencer, Theme Designs, LLC.

The water feature's overall size measured out to 20-feet high by 50 feet wide. To feed the falls, the contractor ran two 2-inch water lines. One line feeds the upper pool and one feeds the lower pool. To push the water, the contractor installed a 2HP 120-gpm centrifugal pump on the 12th floor directly below the swimming pool. The entire project took six weeks to complete, and billed out to more than 1,200 man-hours. The design and project management took an additional 120 hours. All Photos: Erin R. Spencer, Theme Designs, LLC

The Fountains at the Memorial City project in Houston, Texas confronted Theme Designs with a unique waterfall design and installation challenge. The project did not allow for the usual methods of waterfall construction, as it was located on the 13th floor of Metro National's new high-rise luxury apartment complex.

Due to its unique location, Theme Designs had to follow a strict set of criteria in the design and installation of the 2-story vertical faux-rock feature flowing into the Penthouse swimming pool. The client had sketches provided as a conceptual schematic, however, it fell to Theme Designs to make it happen.

According to the contractor, ''Because fiber-reinforced concrete (FRC) casting is an unusual product with specialized installation, Theme Designs hired its own structural engineer to work directly with them and follow the company's direction to produce documents for permit and construction.''

This was Theme Designs initial site visit to the project. The general contractor provided the substructure, which is CMU with core-filled voids. Structural tension cables run horizontally on the upper concrete part. The pool and spa cavities were provided, but with no gunite, piping or electrical wiring.

Keeping the water from the waterfall required creating sides out of rebar and mesh. This part was freeform sculpted due to the narrow sides the contractor had to contend with. Workers cut, bent and anchored the rebar to the rebar frame under the rock panels, and then lath was wired to the frame. Following this, the contractor applied an initial fiber cement mix to create a more detailed rock look.

A Unique Installation

A typical rock waterfall has plenty of floor space to achieve height, and provide a support structure, and allow a nice gentle slope to the top. Weight is usually not an issue, as most waterfalls tend to be on ground level. With little or no floor space and a floating pool deck, the contractor had to keep the rockwork from extending out into the Jacuzzi, pool, or walkway. To accommodate this reality, the contractor suspended the panels from the wall. The panel's weight does not rest upon the pool deck, but rather hangs from a rebar frame and J-anchor epoxy insets into the cinder block wall.

Coordination involved working with numerous other subcontractors since the rockwork was integral to the structure and its facade. Basically, every trade that had point of contact with Theme Design's rockwork needed to be involved in the process.

Shown here is the diamond lath (typically used for stucco) mesh the workers installed to close the gaps between panels and adjoin the substructure. The contractor used roofing paper to prevent the cement mix from falling through.

Workers predrilled and secured the castings in place with J?EUR??,,????'?????<

The electrician installed light fixtures and emergency exit signs recessed in the rockwork. The waterproofing contractor installed a flexible membrane that extended from the roofline, behind the rockwork, and under the floating pool deck to provide a monolithic shell to prevent water from leaking to the floors below. After the anchors were sealed with epoxy, workers installed a flange around all the anchors to maintain the membrane's integrity.

The stucco crew joined the two finishes together. The roofing and gutter contractors provided a water-tight seal at the roofline to keep rainwater contained or in front of the rockwork and not behind it or into the building.

The flooring contractor also was in the mix since he needed to set the finished grade and install his pavers prior to our rockwork installation.

The contractor applied black and pink waterproofing coatings. The Rico Rock panels are made of FRC (fiber reinforced concrete) with a thickness of 3/4-to-1.5 inches and come from castings of real rocks.

Here a worker applies the cement mix. The contractor hand sculpted the ceiling with the wet cement mix.

FRC Panels Verses Real Rocks

For this project, Theme Designs chose Rico Rock FRC panels, which are produced from castings of natural cliff faces. According to the contractor, ''The difference in the weight of real boulders (150 pounds per foot) and FRC panels (10 pounds per face foot) is huge in terms of handling, but even so, the biggest panels weighed more than 400 pounds.'' Getting from the ground level to the penthouse required transporting the rockwork up the outside of the building on open motorized scaffolding.

''Man-handling 400-pound panels on a 2 x 2-inch planks over a 13-story gap was nerve racking, even though the workers were tied off with OSHA-approved safety harnesses and rigging,'' stated the contractor. Once on the pool deck, the panels had to be hand-lifted up to the scaffolding and then lifted up the face of the wall to be bolted to the J-anchors. The waterfall drop was a major design concern for Theme Designs. The drop exceeded their ''Fall/Splash Ratio.'' As explained by the contractor, ''When working with a close walkway, Theme Designs follows the 2:1 formula, which is whatever the fall the furthest drops will be twice the distance dropped. While one can get away with a 1:1 ratio when surrounded by planting, the drop was adjacent to a pedestrian walkway and was guaranteed to splash onto in.'' Theme Designs had to consider the liability issues of water splashing on a slippery paved surface. To work around this, the contractor hand sculpted the sides to contain water splash and wind-driven spray, while still retaining a natural look.

Workers secured the lath to the rebar frame, FRC panels, and then applied the first coat of the cement mix.

Here a worker drills mounting screws into the mesh to secure it to the FRC panels

The two waterfall weirs and sides were 90-percent finished prior to turning on the water.

After turning on the pump, the company performed hand-work to put the water flow just where they wished. They calculated it out to 25gpm per weir foot.

Each panel had to be predrilled at the edges to attach the seaming materials. And the really tricky part is securing the lathe to the back of the panels and not the front so the joint appears natural and not like a ridge or scar that can't be blended into the surrounding cracks and crevices. For a smooth transition when fabricating the joint seam the contractor used their silicone rock texture mats to stamp in natural relief.

The detail shows how the complex installation was secured to the wall.

Per the client's direction, another finish design requirement was matching the rockwork with the color of the natural moss rock boulders in the building's landscape. The acrylic stain used bonds with the FRC so that it does not flake or chip off. The contractor used four different colors and finishes with a dry bush technique for meticulous realism, going as far as to replicate embedded soil and moss growth. The final step was applying an acrylic waterproofing binder to increase the façade's longevity.

From start to finish the project took four weeks to complete, and the crew consisted of 16 workers.